Tagged Phys Ed

Exercise May Ease Hot Flashes, Provided It’s Vigorous

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Hot flashes are a lamentable part of reaching middle age for many women. While drug treatments may provide relief, two new studies suggest that the right type of exercise might lessen both the frequency and discomfiting severity of hot flashes by changing how the body regulates its internal temperature.

As estrogen levels drop with the onset of menopause, many women become less adept, physiologically, at dealing with changes to internal and external temperatures. The result, famously, is the hot flash (also known as a hot flush), during which women can feel sudden, overwhelming heat and experience copious sweating, a problem that in some cases can linger for years.

Hormone replacement therapy can effectively combat hot flashes, and antidepressants may also help, though drug treatments have well-established side effects. Weight loss also may lessen hot flashes, but losing weight after menopause is difficult.

So researchers at Liverpool John Moores University in England and other institutions recently began to consider whether exercise might help.

Endurance exercise, after all, improves the body’s ability to regulate temperature, the scientists knew. Athletes, especially those in strenuous sports like distance running and cycling, start to sweat at a lower body temperature than out-of-shape people. Athletes’ blood vessels also carry more blood to the skin surface to release unwanted heat, even when they aren’t exercising.

If exercise had a similar effect on older, out-of-shape women’s internal thermostats, the scientists speculated, it might also lessen the number or the intensity of their hot flashes.

Previous studies examining exercise as a treatment for hot flashes had shown mixed results, the scientists knew. However, many of those experiments had been short term and involved walking or similarly light exercise, which might be too gentle to cause the physiological changes needed to reduce hot flashes.

So for the two new studies, one of which was published in the Journal of Physiology and the other in Menopause (using the same data to examine different aspects of exercise and hot flashes), the researchers decided to look at the effects of slightly more strenuous workouts.

They first recruited 21 menopausal women who did not currently exercise but did experience hot flashes. According to diaries each woman kept for a week at the start of the study, some women were having 100 or more of them each week.

The scientists also measured each woman’s general health, fitness, blood flow to the brain (which affects heat responses) and, most elaborately, ability to respond to heat stress. For that test, researchers fitted the women with suits that almost completely covered their bodies. The suits contained tubes that could be filled with water. By raising the temperature of the water, the scientists could induce hot flashes — which typically occur if an affected woman’s skin grows hot — and also track her body’s general ability to deal with heat stress.

Fourteen of the women then began an exercise program, while seven, who served as controls, did not. (This was a small pilot study, and the researchers allowed the women to choose whether to exercise or not.)

The sessions, all of them supervised by trainers, at first consisted of 30 minutes of moderate jogging or bicycling three times a week. Gradually, the workouts became longer and more intense, until by the end of four months the women were jogging or pedaling four or five times per week for 45 minutes at a pace that definitely caused them to pant and sweat.

They also, in the last of those 16 weeks, kept another diary of their hot flashes.

Then they returned to the lab to repeat the original tests.

The results showed that the exercisers, unsurprisingly, were considerably more aerobically fit now, while the control group’s fitness was unchanged.

More striking, the women who had exercised showed much better ability to regulate their body heat. When they wore the suit filled with warm water, they began to sweat a little earlier and more heavily than they had before, showing that their bodies could generally dissipate heat better.

But at the same time, during an actual hot flash induced by the hot suit, the exercisers perspired less and showed a lower rise in skin temperature than the control group. Their hot flashes were less intense than those of the women who had not worked out.

Probably best of all from the standpoint of the volunteers who had exercised, they turned out to have experienced far fewer hot flashes near the end of the experiment, according to their diaries, with the average frequency declining by more than 60 percent.

These findings strongly suggest that “improvements in fitness with a regular exercise program will have potential benefits on hot flushes,” said Helen Jones, a professor of exercise science at Liverpool John Moores University, who oversaw the new studies.

Precisely how exercise might change a women’s susceptibility to hot flashes is still not completely clear, although the researchers noted that the women who exercised developed better blood flow to the surface of their skin and to their brains during heat stress. That heightened blood flow most likely aided the operations of portions of the brain that regulate body temperature, Dr. Jones said.

The cautionary subtext of this study, though, is that to be effective against hot flashes, exercise probably needs to be sustained and somewhat strenuous, she said. “A leisurely walk for 30 minutes once a week is not going to have the required impact.”

To Boost Memory: Study, Wait, Then Exercise

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Learning requires more than the acquisition of unfamiliar knowledge; that new information or know-how, if it’s to be more than ephemeral, must be consolidated and securely stored in long-term memory.

Mental repetition is one way to do that, of course. But mounting scientific evidence suggests that what we do physically also plays an important role in this process. Sleep, for instance, reinforces memory. And recent experiments show that when mice and rats jog on running wheels after acquiring a new skill, they learn much better than sedentary rodents do. Exercise seems to increase the production of biochemicals in the body and brain related to mental function.

Researchers at the Donders Institute for Brain, Cognition and Behavior at Radboud University in the Netherlands and the University of Edinburgh have begun to explore this connection. For a study published this month in Current Biology, 72 healthy adult men and women spent about 40 minutes undergoing a standard test of visual and spatial learning. They observed pictures on a computer screen and then were asked to remember their locations.

Afterward, the subjects all watched nature documentaries. Two-thirds of them also exercised: Half were first put through interval training on exercise bicycles for 35 minutes immediately after completing the test; the others did the same workout four hours after the test.

Two days later, everyone returned to the lab and repeated the original computerized test while an M.R.I. machine scanned their brain activity.

Those who exercised four hours after the test recognized and recreated the picture locations most accurately. Their brain activity was subtly different, too, showing a more consistent pattern of neural activity. The study’s authors suggest that their brains might have been functioning more efficiently because they had learned the patterns so fully. But why delaying exercise for four hours was more effective than an immediate workout remains mysterious. By contrast, rodents do better in many experiments if they work out right after learning.

Eelco van Dongen, the study’s lead author and a former researcher at Radboud University (he is now a policy officer at the Netherlands Organization for Scientific Research), hopes that future studies will help determine both the optimal time to exercise and the ideal activity to reinforce learning. Workouts that are too strenuous “could be less positive or even detrimental” to acquiring knowledge, Dr. van Dongen says, while gentle exertions — “a short, slow walk,” he adds — might not prompt enough of an increase in the biochemicals needed to influence how the brain learns.

For now, he says, if you are trying to memorize a PowerPoint narrative or teach yourself macroeconomics, it could be beneficial to exercise a few hours after a study session. “Long-term memory is not only influenced by what happens when you learn new things,” he says, “but also by the processes that take place in the hours and days afterward, when new information is stabilized and integrated in your brain.”

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Being Unfit May Be Almost as Bad for You as Smoking

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Being out of shape could be more harmful to health and longevity than most people expect, according to a new, long-term study of middle-aged men. The study finds that poor physical fitness may be second only to smoking as a risk factor for premature death.

It is not news that aerobic capacity can influence lifespan. Many past epidemiological studies have found that people with low physical fitness tend to be at high risk of premature death. Conversely, people with robust aerobic capacity are likely to have long lives.

But most of those studies followed people for about 10 to 20 years, which is a lengthy period of time for science but nowhere near most of our actual lifespans. Some of those studies also enrolled people who already were elderly or infirm, making it difficult to extrapolate the findings to younger, healthier people.

So for the new study, which was published this week in the European Journal of Preventive Cardiology, researchers from the University of Gothenburg in Sweden and other institutions turned to an impressively large and long-term database of information about Swedish men.

The data set, prosaically named the Study of Men Born in 1913, involved exactly that. In 1963, almost 1,000 healthy 50-year-old men in Gothenburg who had been born in 1913 agreed to be studied for the rest of their lives, in order to help scientists better understand lifetime risks for disease, especially heart disease.

The men completed baseline health testing in 1963, including measures of their blood pressure, weight and cholesterol, and whether they exercised and smoked. Four years later, when the volunteers were 54, some underwent more extensive testing, including an exercise stress test designed to precisely determine their maximum aerobic capacity, or VO2 max. Using the results, the scientists developed a mathematical formula that allowed them to estimate the aerobic capacity of the rest of the participants.

Aerobic capacity is an interesting measure for scientists to study, because it is affected by both genetics and lifestyle. Some portion of our VO2 max is innate; we inherit it from our parents. But much of our endurance capacity is determined by our lifestyle. Being sedentary lowers VO2 max, as does being overweight. Exercise raises it.

Among this group of middle-aged men, aerobic capacities ranged from slight to impressively high, and generally reflected the men’s self-reported exercise habits. Men who said that they seldom worked out tended to have a low VO2 max. (Because VO2 max is more objective than self-reports about exercise, the researchers focused on it.)

To determine what impact fitness might have on lifespan, the scientists grouped the men into three categories: those with low, medium or high aerobic capacity at age 54.

Then they followed the men for almost 50 years. During that time, the surviving volunteers completed follow-up health testing about once each decade. The scientists also tracked deaths among the men, based on a national registry.

Then they compared the risk of relatively early death to a variety of health parameters, particularly each man’s VO2 max, blood pressure, cholesterol profile and history of smoking. (They did not include body weight as a separate measure, because it was indirectly reflected by VO2 max.)

Not surprisingly, smoking had the greatest impact on lifespan. It substantially shortened lives.

But low aerobic capacity wasn’t far behind. The men in the group with the lowest VO2 max had a 21 percent higher risk of dying prematurely than those with middling aerobic capacity, and about a 42 percent higher risk of early death than the men who were the most fit.

Poor fitness turned out to be unhealthier even than high blood pressure or poor cholesterol profiles, the researchers found. Highly fit men with elevated blood pressure or relatively unhealthy cholesterol profiles tended to live longer than out-of-shape men with good blood pressure and cholesterol levels.

Of course, this study found links between poor fitness and shortened lifespans. It cannot prove that one caused the other, or explain how VO2 max might affect lifespan. However, the findings raise the possibility, as the scientists speculate, that by strengthening the body, better fitness may lower the risk of a variety of chronic diseases.

This study also involved men — and Swedish men at that. So whether the findings are applicable to other people, particularly women, is uncertain.

But “there is no reason not to think” that the rest of us would also share any beneficial associations between fitness and longevity, said Per Ladenvall, a researcher at the Sahlgrenska Academy at the University of Gothenburg, who led the study. Past studies involving women have found such links, he said.

Encouragingly, if you now are concerned about the state of your particular aerobic capacity, you most likely can increase it just by getting up and moving. “Even small amounts of physical activity,” Dr. Ladenvall said, “may have positive effects on fitness.”

Lifting Lighter Weights Can Be Just as Effective as Heavy Ones

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Upending conventions about how best to strength train, a new study finds that people who lift relatively light weights can build just as much strength and muscle size as those who grunt through sessions using much heftier weights — if they plan their workouts correctly.

Strength training has long been dominated by the idea that to develop a physique like that of Charles Atlas or even Zac Efron, we — and I include women here — must load our barbells or machines with almost as much weight as we can bear.

In traditional weight training programs, in fact, we are told to first find the heaviest amount of weight that we possibly can lift one time. This is our one-repetition maximum weight. We then use this to shape the rest of the program by lifting 80 to 90 percent of that amount eight to 10 times, until our affected arms or legs shake with fatigue.

This approach to weight training is very effective, says Stuart Phillips, a professor of kinesiology at McMaster University in Hamilton, Ontario, who has long studied muscles and exercise. It builds muscle strength and size, possibly, many experts believe, by sparking a surge in the body’s production of testosterone and human growth hormone.

But many people find lifting such heavy weights to be daunting or downright unpleasant, which can discourage them from taking up or continuing with a resistance-training program, Dr. Phillips says.

So in recent years, he and his colleagues have been looking into the effects of a different type of weight training, which employs much lighter weights hefted through as many as 25 repetitions.

Since 2010, his lab has published several studies in which volunteers followed either the traditional regimen using heavy weights or an alternative that employed much slighter weight stacks. In general, the lifters’ results were comparable.

But those studies had been small and featured volunteers who were new to the gym, potentially skewing the outcomes, Dr. Phillips says. Almost everyone who takes up weight training shows significant improvements in strength and muscle size, making it difficult to tease out the impacts of one version of training versus another.

So for the new study, which was funded by the Natural Sciences and Engineering Research Council of Canada and published this month in the Journal of Applied Physiology, he and his colleagues recruited 49 young men who had been weight training for a year or more. (The scientists plan to study women and older people in future studies.)

All completed tests of strength, fitness, hormone levels and muscular health, then were randomly divided into two groups.

One group was assigned to follow the standard regimen, in which weights were set at between 75 and 90 percent of the man’s one-repetition maximum and the volunteer lifted until he could not lift again, usually after about 10 repetitions.

The other volunteers began the lighter routine. Their weights were set at between 30 and 50 percent of each man’s one-repetition maximum, and he lifted them as many as 25 times, until the muscles were exhausted.

All of the volunteers performed three sets of their various lifts four times per week for 12 weeks.

Then they returned to the lab to have muscle strength, size and health reassessed and their hormone levels re-measured.

The results were unequivocal. There were no significant differences between the two groups. All of the men had gained muscle strength and size, and these gains were almost identical, whether they had lifted heavy or light weights.

Interestingly, the scientists found no connection between changes in the men’s hormone levels and their gains in strength and muscle size. All of the men had more testosterone and human growth hormone flowing through their bodies after the workouts. But the degree of those changes in hormone levels did not correlate with their gains in strength.

Instead, the key to getting stronger for these men, Dr. Phillips and his colleagues decided, was to grow tired. The volunteers in both groups had to attain almost total muscular fatigue in order to increase their muscles’ size and strength.

That finding suggests, Dr. Phillips says, that there is something about the cellular mechanisms jump-started in muscle tissue by exhaustion that enables you to develop arms like the first lady’s.

This data does not prove, though, that one approach to lifting weights is necessarily better than the other, Dr. Phillips says.

“But some people will find it much easier or less intimidating” to lift lighter weights, he says, even though they need to complete more repetitions in order to tire their muscles. They also may experience fewer injuries, he says, although that possibility has not yet been tested.

For now, someone hoping to strengthen his or her muscles should choose a weight that feels tolerable and then lift it repeatedly until the effort of the final lift is at least an eight on a scale of one to 10, Dr. Phillips says. “There should be some discomfort,” he says, “but the dividends on the back side” in terms of stronger, healthier muscles “are enormous.”

Can Running Make You Smarter?

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To strengthen your mind, you may first want to exert your leg muscles, according to a sophisticated new experiment involving people, mice and monkeys. The study’s results suggest that long-term endurance exercise such as running can alter muscles in ways that then jump-start changes in the brain, helping to fortify learning and memory.

I often have written about the benefits of exercise for the brain and, in particular, how, when lab rodents or other animals exercise, they create extra neurons in their brains, a process known as neurogenesis. These new cells then cluster in portions of the brain critical for thinking and recollection.

Even more telling, other experiments have found that animals living in cages enlivened with colored toys, flavored varieties of water and other enrichments wind up showing greater neurogenesis than animals in drab, standard cages. But animals given access to running wheels, even if they don’t also have all of the toys and other party-cage extras, develop the most new brain cells of all.

These experiments strongly suggest that while mental stimulation is important for brain health, physical stimulation is even more potent.

But so far scientists have not teased out precisely how physical movement remakes the brain, although all agree that the process is bogglingly complex.

Fascinated by that complexity, researchers at the National Institutes of Health recently began to wonder whether some of the necessary steps might be taking place far from the brain itself, and specifically, in the muscles, which are the body part most affected by exercise. Working muscles contract, burn fuel and pump out a wide variety of proteins and other substances.

The N.I.H. researchers suspected that some of those substances migrated from the muscles into the bloodstream and then to the brain, where they most likely contributed to brain health.

But which substances were involved was largely a mystery.

So for the new study, which was published last month in Cell Metabolism, the N.I.H. researchers first isolated muscle cells from mice in petri dishes and doused them with a peptide that affects cell metabolism in ways that mimic aerobic exercise. In effect, they made the cells think that they were running.

Then, using a technique called mass spectrometry, the scientists analyzed the many chemicals that the muscle cells released after their pseudo-workouts, focusing on those few that can cross the blood-brain barrier.

They zeroed in on one substance in particular, a protein called cathepsin B. The protein is known to help sore muscles recover, in part by helping to clear away cellular debris, but it had not previously been considered part of the chain linking exercise to brain health.

To determine whether cathepsin B might, in fact, be involved in brain health, the researchers added a little of the protein to living neurons in other petri dishes. They found that those brain cells started making more proteins related to neurogenesis.

Cathepsin B also proved to be abundant in the bloodstreams of mice, monkeys and people who took up running, the scientists found. In experiments undertaken in collaboration with colleagues in Germany, the researchers had mice run for several weeks, while rhesus monkeys and young men and women took to treadmills for four months, exercising vigorously about three times a week for approximately an hour or sometimes longer.

During that time, the concentrations of cathepsin B in the jogging animals and people steadily rose, the researchers found, and all of the runners began to perform better on various tests of memory and thinking.

Most striking, in the human volunteers, the men and women whose fitness had increased the most — suggesting that they had run particularly intensely — not only had the highest levels of cathepsin B in their blood but also the most-improved test scores.

Finally, because there’s nothing like removing something from the body to underscore how important it may be, the scientists bred mice without the ability to create cathepsin B, including after exercise. The researchers had those mice and other, normal animals run for a week, then taxed their ability to learn and retain information.

After running, the normal mice learned more rapidly than they had before and also held on to those new memories well. But the animals that could not produce cathepsin B learned haltingly and soon forgot their new skills. Running had not helped them to become smarter.

The lesson of these experiments is that our brains appear to function better when they are awash in cathepsin B and we make more cathepsin B when we exercise, says Henriette van Praag, an investigator at the National Institute on Aging at the N.I.H. who oversaw this study.

Of course, increases in cathepsin B explain only part of the benefits of exercise for the brain, she said. She and her colleagues plan to continue looking for other mechanisms in future studies.

They also hope to learn more about how much exercise is necessary to gain brain benefits. The regimen that the human runners followed in this study was “fairly intensive,” she said, but it’s possible that lighter workouts would be almost as effective.

“There is good reason to think,” she said, “that any amount of exercise is going to be better than none” for brain health.

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The Surprising Health Benefits of an Electric Bike

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In the Tour de France, equipping your bike with a small electric motor is called mechanical doping, and is considered cheating. But for the rest of us, an electrified bicycle might be a way to make exercise both tolerable and practical, according to an encouraging new study of bicycle commuting.

Exercise is necessary in our lives, as we all know by now. People who are physically active are much less likely than sedentary people to develop heart disease, diabetes, cancer, stroke, depression, disabilities in old age, or to die prematurely.

But statistics show that, despite its benefits, a majority of us never exercise. When researchers ask why, most people offer the same two excuses — they don’t have time to fit exercise into their lives or they aren’t fit enough to undertake exercise.

Potentially, electric bicycles could address those concerns. Their motors shore up your pedaling as needed—or, with some electric bikes, do the pedaling for you—making climbing hills or riding for long distances less taxing and daunting than the same ride on a standard bicycle.

In the process, they could make cycling a palatable alternative to commuting by car, allowing people with jammed daily schedules to work out while getting to work.

But the value of electric bicycles has so far been mostly notional. Few of us have seen, let alone ridden, an electric bike and there is scant scientific evidence supporting—or refuting—the potential health benefits of using the machines.

So for the new experiment, which was published last month in the European Journal of Applied Physiology, researchers at the University of Colorado, Boulder, decided to see what would happen if they gave a group of out-of-shape men and women zippy electric bikes and suggested that they begin riding to work.

Notably, the researchers only studied motorized bikes that assist the rider rather than doing all the work for them, like a moped. They used electric bikes that require the rider to pedal in order to receive assistance from the motor.

The researchers wanted to determine whether these bikes — even with the added assistance of a motor — would provide a meaningful workout for people who previously had not been exercising much. They also wanted to see whether such bikes were fundamentally safe, given that they enable even novice riders to achieve speeds of 20 miles per hour or higher. (The Boulder city government partially funded the study as part of an assessment of whether to allow electric bikes on municipal bike paths. Additional funding came from local bike shops and Skratch Labs, a sports nutrition company in Boulder.)

The researchers first brought their 20 sedentary volunteers into the lab to check their body composition, aerobic fitness, blood sugar control, blood pressure and cholesterol profiles. Then they provided each with an electric bicycle, heart rate monitor, GPS device, instructions on the use of all of this equipment, and asked each volunteer to don the monitors and ride his or her new bike to and from work at least three times a week for the next month, spending at least 40 minutes in the saddle on those days.

The volunteers were directed to choose whatever speed and effort felt comfortable for them.

Then the researchers loosed the novice riders onto Boulder’s roads and bike paths.

A month later, the volunteers returned to the lab to repeat the original tests and turn over heart rate and GPS data. All of them had ridden at least the prescribed minimum of 40 minutes three times per week and in fact, according to their monitor data, most had ridden more than required, several about 50 percent more.

The riders also had ridden with some intensity. Their heart rates averaged about 75 percent of each person’s maximum, meaning that even with the motor assist, they were getting a moderate workout, comparable to brisk walking or an easy jog.

But thankfully none had crashed and hurt themselves (or anyone else). In fact, “we found that participants rode at a reasonable average speed of about 12 miles per hour,” said James Peterman, a graduate student at U.C. Boulder who led the study.

Perhaps most important, the riders were healthier and more fit now, with significantly greater aerobic fitness, better blood sugar control, and, as a group, a trend toward less body fat.

They also reported finding the riding to “be a blast,” said William Byrnes, the study’s senior author and director of the university’s Applied Exercise Science Laboratory. “It’s exercise that is fun.”

Several participants have bought electric bikes since the study ended, he said. He also rides an electric bike to and from campus.

Electric bikes are unlikely to be a solution for everyone who is pressed for time or reluctant to exercise, though. The bikes are pricey, typically retailing for thousands of dollars.

They also offer less of a workout than non-motorized bicycles. Mr. Peterman, an accomplished bike racer who placed fifth in the time trial at the United States National Cycling Championships last week admits that motorized bicycles are unlikely to goose the fitness of well-trained athletes.

But for the many other people who currently do not exercise or have never considered bike commuting, there is much to be said for knowing that, if needed, you can get a little help pedaling up that next hill.

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Could Environmental Chemicals Shape Our Exercise Habits?

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A disquieting new study finds that mice exposed prenatally to a common chemical found in many cosmetics and personal care products are less likely than other mice to exercise as adults, adding a new wrinkle to the mystery of exercise motivation. Although mice obviously are not people, the findings at least raise the possibility that exposure to environmental toxins before birth might change babies’ physiology in ways that affect their interest in exercise throughout their lives.

By now, we all know that we should work out to improve health and well-being. But a hefty majority of us never manage to exercise and many who do visit the gym do so reluctantly and sporadically.

The question of why some people are so loath to exercise is of pressing interest to exercise scientists. Work and family obligations of course play an outsize role, as do genes. Studies of the genetics of exercise suggest in fact that the will to exercise — or not — is mostly inherited.

But scientists also have begun to wonder about early physical development and whether differences in the environment within a mother’s womb might lead to changes in her baby that affect how much that infant moves around later in life.

A mouse study I wrote about recently suggested, encouragingly, that if a mother exercises during pregnancy, she might increase her offspring’s subsequent interest in working out.

But whether the environment within the womb might reduce a baby’s later desire to exercise has not been much studied.

So for the new study, which will appear next month in Medicine & Science in Sports & Exercise, scientists at Texas A&M University in College Station, Tex., decided to look at pregnancy, exercise behavior and phthalates.

Phthalates (THAL-ates) are a class of chemicals used as solvents and fixatives and to make plastic pliable. Found today in a boggling array of everyday products, from food containers to shampoos and perfume, they are virtually ubiquitous in the environment and in our bloodstreams.

They easily cross into a pregnant woman’s womb and accumulate in her offspring. Rather ominously, phthalates are known as endocrine disrupters, meaning that they can change the body’s production of the sex hormones testosterone and estrogen and, in animal studies, alter the onset of puberty in mouse pups exposed to high levels of the chemicals in utero.

The Texas scientists wondered whether phthalates might also influence how much exposed babies exercised, since varying levels of sex hormones, especially testosterone, are known to change how readily young animals move around.

To find out, they gathered healthy female mice, mated them with healthy males, and then fed half of the pregnant females benzyl butyl phthalate (B.B.P.), a common phthalate. The mice received the B.B.P. at the point in their pregnancies when their babies were rapidly developing organs and sex characteristics, which in human terms, would be near the end of the second trimester.

According to the scientists’ calculations, the exposure for each pup would be slightly higher than the amount that the E.P.A. has determined to be safe for humans.

The rest of the pregnant animals were fed a harmless oil to serve as a control group.

After birth, all of the pups were provided with running wheels and allowed to exercise as much or little as they chose.

The scientists checked the animals’ sex hormone levels at several points during the animals’ lives.

What the researchers found was that by young adulthood and continuing on into the mouse version of late middle age, the exposed animals were not moving much.

In fact, the male mice that had been exposed to B.B.P. in utero ran about 20 percent less during adulthood than the other animals, while the exposed females exercised about 15 percent less.

Interestingly, the exposed animals did not differ much from the other rodents in terms of body composition. They were not significantly fatter. Obesity and any accompanying disability had not discouraged them from exercising, the scientists concluded. They had been sedentary by choice, not necessity.

That choice, however, seems to have been influenced by disruptions in their sex hormones. Checking their data, the researchers found that the male mice exposed to B.B.P. in utero had notably lower levels of testosterone than the other animals in young adulthood, which is also when their running mileage cratered. Those differences lingered into middle age. The exposed females similarly developed during young adulthood low estrogen levels and other reproductive system abnormalities that then produced a profound desire, it seems, to sit for most of the day.

The implication of these findings is that, in mice, “exposure to the endocrine disrupter B.B.P. might affect lifelong physical activity,” said Emily Schmitt, a postdoctoral researcher at Texas A&M who led the new study.

It’s impossible at this point to say whether human babies would be similarly affected, Dr. Schmitt said.

Likewise scientists don’t know whether a father’s exposure to phthalates can affect his unborn offspring or if eating and dousing oneself in phthalates long after birth, including when you are fully grown, might dampen your subsequent enthusiasm for working out, although Dr. Schmitt and her colleagues hope to investigate some of those issues in future studies.

But even with many questions remaining unanswered, “it certainly seems like a good idea to try to avoid endocrine disruptors as much as possible, especially if you are pregnant,” Dr. Schmitt said.

You can find tips for reducing exposure to the chemicals at saferchemicals.org/.

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How Many Calories We Burn When We Sit, Stand or Walk

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There are many compelling reasons to get up out of your desk chair and stand more at work. But weight control is probably not one of them, according to a new study that precisely measured how many calories people burn during everyday office activities.

The new study’s results suggest that engaging frequently in one type of activity while at work may help many of us avoid weight gain. But that activity is not standing up.

Most of us sit more than we should, and a majority of our sitting time occurs at work, since many modern professions are sedentary. Many of us spend six or seven hours tied to our desks each day.

These long, uninterrupted periods of physical lethargy have been linked with increased risks for diabetes, heart disease, premature mortality and, not least, weight gain.

In response, many people, including me, have begun to look for ways to break up our sitting time. We download smartphone apps that chirp and tell us to stand up several times every hour. Health-minded supervisors organize walking meetings, in which employees discuss business while hoofing along hallways. And standing desks have become so popular that the satirical website The Onion has poked fun at users, declaring “Standing at Work Can Increase Coworkers’ Disdain Up to 70 Percent.”

Recent studies indicate that measures that get us off our seats can help us better regulate blood sugar and lessen the risks for diabetes and chronic disease. But more to the point, many of us are rising from our chairs in the hopes that sitting less will help keep our waistlines and nether quarters from spreading.

Surprisingly few studies, however, have closely tracked how many additional calories we burn if we stand up or walk around our offices.

So for the new experiment, which was published this month in the Journal of Physical Activity and Health, researchers affiliated with the Physical Activity and Weight Management Research Center at the University of Pittsburgh rounded up 74 healthy volunteers. Most were in their mid-20s, of normal weight, and with some acquaintance with office life.

These volunteers were randomly assigned to four different groups. One group was asked to sit and type at a computer for 15 minutes and then stand up for 15 minutes, moving around and fidgeting as little as possible.

Another group also sat for 15 minutes, but watched a television screen and didn’t type. Afterward, they immediately moved to a treadmill and walked for 15 minutes at a gentle, strolling pace.

The third group stood up for 15 minutes and then sat down for 15 minutes.

And the final group walked on the treadmills for 15 minutes and then sat.

Throughout, the volunteers wore masks that precisely measured their energy expenditure, which means how many calories they were using.

Unsurprisingly, sitting was not very taxing. The volunteers generally burned about 20 calories during their 15 minutes of sitting, whether they were typing or staring at a television screen.

More unexpected, standing up was barely more demanding. While standing for 15 minutes, the volunteers burned about 2 additional calories compared to when they sat down. It didn’t matter whether they stood up and then sat down or sat down and then stood up. The total caloric expenditure was about the same and was not sizable.

Over all, in fact, the researchers concluded, someone who stood up while working instead of sitting would burn about 8 or 9 extra calories per hour. (Just for comparison, a single cup of coffee with cream and sugar contains around 50 calories.)

But walking was a different matter. When the volunteers walked for 15 minutes, even at a fairly easy pace, they burned about three times as many calories as when they sat or stood. If they walked for an hour, the researchers calculated, they would incinerate about 130 more calories than if they stayed in their chairs or stood up at their desks, an added energy expenditure that might be sufficient, they write, to help people avoid creeping, yearly weight gain.

The upshot of this experiment is that if your goal is to control your weight at work, then “standing up may not be enough,” said Seth Creasy, a graduate student at the University of Pittsburgh and the lead author of the new study.

You probably need to also incorporate walking into your office routine, he said. Maybe “put the printer at the other end of the hallway, or get up to walk to the water fountain every hour or so” instead of keeping a water bottle at your desk.

“Brief periods of walking can add up to make a big difference” in energy expenditure, he said, while standing barely budges your caloric burn.

Of course, standing up almost certainly has other health benefits apart from weight management, Mr. Creasy said, including better blood sugar control and less back and shoulder pain associated with hunching in a chair all day. So don’t dismantle or abandon your stand-up desk just yet. But don’t expect it to counteract that extra cookie with lunch.

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How Exercise May Help the Brain Grow Stronger

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Physical activity is good for our brains. A wealth of science supports that idea. But precisely how exercise alters and improves the brain remains somewhat mysterious.

A new study with mice fills in one piece of that puzzle. It shows that, in rodents at least, strenuous exercise seems to beneficially change how certain genes work inside the brain. Though the study was in mice, and not people, there are encouraging hints that similar things may be going on inside our own skulls.

For years, scientists have known that the brains of animals and people who regularly exercise are different than the brains of those who are sedentary. Experiments in animals show that, for instance, exercise induces the creation of many new cells in the hippocampus, which is a part of the brain essential for memory and learning, and also improves the survival of those fragile, newborn neurons.

Researchers believe that exercise performs these feats at least in part by goosing the body’s production of a substance called brain-derived neurotropic factor, or B.D.N.F., which is a protein that scientists sometimes refer to as “Miracle-Gro” for the brain. B.D.N.F. helps neurons to grow and remain vigorous and also strengthens the synapses that connect neurons, allowing the brain to function better. Low levels of B.D.N.F. have been associated with cognitive decline in both people and animals. Exercise increases levels of B.D.N.F. in brain tissue.

But scientists have not understood just what it is about exercise that prompts the brain to start pumping out additional B.D.N.F.

So for the new study, which was published this month in the journal eLIFE, researchers with New York University’s Langone Medical Center and other institutions decided to microscopically examine and reverse engineer the steps that lead to a surge in B.D.N.F. after exercise.

They began by gathering healthy mice. Half of the animals were put into cages that contained running wheels. The others were housed without wheels. For a month, all of the animals were allowed to get on with their lives. Those living with wheels ran often, generally covering several miles a day, since mice like to run. The others remained sedentary.

After four weeks, the scientists looked at brain tissue from the hippocampus of both groups of animals, checking for B.D.N.F. levels. As expected, the levels were much higher in the brains of the runners.

But then, to better understand why the runners had more B.D.N.F., the researchers turned to the particular gene in the animals’ DNA that is known to create B.D.N.F. For some reason, the scientists realized, this gene was more active among the animals that exercised than those that did not.

Using sophisticated testing methods, the scientists soon learned why. In both groups of animals, the B.D.N.F. gene was partially covered with clusters of a particular type of molecule that binds to the gene, though in different amounts.

In the sedentary mice, these molecules swarmed so densely over the gene that they blocked signals that tell the gene to turn on. As a result, the B.D.N.F. genes of the sedentary animals were relatively muted, pumping out little B.D.N.F.

But among the runners, the molecular blockade was much less effective. The molecules couldn’t seem to cover and bind to the entire B.D.N.F. gene. So messages from the body continued to reach the gene and tell it to turn on and produce more B.D.N.F.

Perhaps most remarkably, the researchers also found a particular substance in the runners’ brains that fended off the action of these obstructionist molecules. The runners’ brains contained high levels of ketones, which are a byproduct of the breakdown of fat. During strenuous exercise, the body relies in part on fat for fuel and winds up creating ketones, some of which migrate to the brain. (They are tiny enough to cross the blood-brain barrier.) The brain uses these ketones for fuel when blood sugar levels grow low.

But it appears that ketones also cause the molecules that hinder the B.D.N.F. gene to loosen their grip, as the scientists realized when they experimentally added ketones to brain tissue from some of the mice. Afterward, their B.D.N.F. genes were not blocked by nearly as many of the bothersome molecules, and those genes could get on with the job of making B.D.N.F.

None of this occurred in the brains of the sedentary mice.

“It’s incredible just how pervasive and complex the effects of exercise are on the brain,” said Moses Chao, a professor at the Skirball Institute of Biomolecular Medicine at N.Y.U. who oversaw the study.

Whether the same mechanisms that occur in mice occur in our own brains when we exercise is still unknown. But, Dr. Chao pointed out, like the mice, we have more B.D.N.F. in our bodies after exercise. We also create ketones when we exercise, and those ketones are known to migrate to our brains..

Generally, however, this process requires exerting yourself vigorously for an hour or more, after which time your body, having exhausted its stores of sugar, starts burning stored fat and making ketones.

If an hour or more of intense exercise seems daunting — and it does to me — don’t despair. “We are only starting to understand” the many ways in which exercise of any kind and amount is likely to alter our brains, Dr. Chao said. For now, he says, “it’s a very good idea to just keep moving.”

Yoga May Be Good for the Brain

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A weekly routine of yoga and meditation may strengthen thinking skills and help to stave off aging-related mental decline, according to a new study of older adults with early signs of memory problems.

Most of us past the age of 40 are aware that our minds and, in particular, memories begin to sputter as the years pass. Familiar names and words no longer spring readily to mind, and car keys acquire the power to teleport into jacket pockets where we could not possibly have left them.

Some weakening in mental function appears to be inevitable as we age. But emerging science suggests that we might be able to slow and mitigate the decline by how we live and, in particular, whether and how we move our bodies. Past studies have found that people who run, weight train, dance, practice tai chi, or regularly garden have a lower risk of developing dementia than people who are not physically active at all.

There also is growing evidence that combining physical activity with meditation might intensify the benefits of both pursuits. In an interesting study that I wrote about recently, for example, people with depression who meditated before they went for a run showed greater improvements in their mood than people who did either of those activities alone.

But many people do not have the physical capacity or taste for running or other similarly vigorous activities.

So for the new study, which was published in April in the Journal of Alzheimer’s Disease, researchers at the University of California, Los Angeles, and other institutions decided to test whether yoga, a relatively mild, meditative activity, could alter people’s brains and fortify their ability to think.

They began by recruiting 29 middle-aged and older adults from the Los Angeles area who told the researchers that they were anxious about the state of their memories and who, during evaluations at the university, were found to have mild cognitive impairment, a mental condition that can be a precursor to eventual dementia.

The volunteers also underwent a sophisticated type of brain scan that tracks how different parts of the brain communicate with one another.

The volunteers then were divided into two groups. One began a well-established brain-training program that involves an hour a week of classroom time and a series of mental exercises designed to bolster their memory that volunteers were asked to practice at home for about 15 minutes a day.

The others took up yoga. For an hour each week, they visited the U.C.L.A. campus to learn Kundalini yoga, which involves breathing exercises and meditation as well as movement and poses. The researchers chose this form of yoga largely because people who are out of shape or new to yoga generally find it easy to complete the classes.

The yoga group also was taught a type of meditation known as Kirtan Kriya that involves repeating a series of sounds — a mantra — while simultaneously “dancing” with repetitive hand movements. They were asked to meditate in this way for 15 minutes every day, so that the total time commitment was equivalent for both groups.

The volunteers practiced their programs for 12 weeks.

Then they returned to the university’s lab for another round of cognitive tests and a second brain scan.

By this time, all of the men and women were able to perform significantly better on most tests of their thinking.

But only those who had practiced yoga and meditation showed improvements in their moods — they scored lower on an assessment of potential depression than those in the brain-training group — and they performed much better on a test of visuospatial memory, a type of remembering that is important for balance, depth perception and the ability to recognize objects and navigate the world.

The brain scans in both groups displayed more communication now between parts of their brains involved in memory and language skills. Those who had practiced yoga, however, also had developed more communication between parts of the brain that control attention, suggesting a greater ability now to focus and multitask.

In effect, yoga and meditation had equaled and then topped the benefits of 12 weeks of brain training.

“We were a bit surprised by the magnitude” of the brain effects, said Dr. Helen Lavretsky, a professor of psychiatry at U.C.L.A. who oversaw the study.

How, physiologically, yoga and meditation had uniquely changed the volunteers’ brains is impossible to know from this study, although reductions in stress hormones and anxiety are likely to play a substantial role, she said. “These were all people worried about the state of their minds,” she pointed out.

Movement also increases the levels of various biochemicals in the muscles and brains that are associated with improved brain health, she said.

Whether other forms of yoga and meditation or either activity on its own might likewise bulk up the brain remains a mystery, she said. But there may be something especially potent, she said, about combining yoga with the type of meditation practiced in this study, during which people were not completely still.

The Alzheimer’s Research and Prevention Foundation, which partially funded this study, provides information on its website about how to start meditating in this style, if you would like to try.

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Exercise Tied to Lower Risk for 13 Types of Cancer

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Anyone who still needs motivation to move more may find it in a new study showing that, in addition to its other health benefits, exercise appears to substantially reduce the risk of developing 13 different varieties of cancer. That is far more types than scientists previously thought might be impacted by exercise. The comprehensive study also suggests that the potential cancer-fighting benefits of exercise seem to hold true even if someone is overweight.

The idea that exercise might change someone’s susceptibility to cancer is, of course, not new. Many studies have found that people who are physically active, either through exercise or while on the job, tend to be less likely to develop certain types of cancer than people who are sedentary.

But those studies primarily looked at associations between exercise and a few common malignancies, such as breast cancer in women, and colon and lung cancers in both women and men.

Whether physical activity, and more precisely, regular exercise, would also lower our risk for other cancers has remained an open question.

So for the new study, which was published this week in JAMA Internal Medicine, scientists with the division of cancer epidemiology and genetics at the National Cancer Institute, as well as Harvard Medical School, and a number of other institutions around the world turned to a large trove of epidemiological health studies conducted in the United States or Europe.

In these earlier studies, researchers directly measured volunteers’ body mass and other health markers and also asked about their diets and exercise habits. The researchers then tracked the participants for a decade or more, noting disease diagnoses or, in some instances, deaths.

Such studies help to establish links between lifestyles and disease risk. But the number of people involved must be hefty if the associations are to be persuasive.

To gain sufficient numbers now, the Cancer Institute researchers gathered data from 12 large-scale studies that, pooled together, involved 1.44 million men and women.

The researchers focused on specific information for each of those 1.44 million people about whether they exercised, and how vigorously and how often. They also zeroed in on whether and when, after each study’s start, the participant had been diagnosed with any type of cancer.

Then, using elaborate statistical methods, they computed the role that exercise, and in particular, moderate or vigorous exercise such as brisk walking or jogging, seemed to be playing in people’s risks for cancer.

It turned out to be considerable. For most cancers, people who reported exercising moderately, even if the time that they spent exercising was slight, had significantly less risk of developing 13 different types of cancer than people who were sedentary.

The researchers found a reduced risk of breast, lung and colon cancers, which had been reported in earlier research. But they also found a lower risk of tumors in the liver, esophagus, kidney, stomach, endometrium, blood, bone marrow, head and neck, rectum and bladder.

And the reductions in risk for any of these 13 cancers rose steeply as people exercised more. When the researchers compared the top 10 percent of exercisers, meaning those who spent the most time each week engaging in moderate or vigorous workouts, to the 10 percent who were the least active, the exercisers were as much as 20 percent less likely to develop most of the cancers in the study.

On the other hand, they found an increased risk of two types of malignancies — melanoma and slow-growing prostate tumors — among people who exercised the most. Those findings can most likely be explained, in large part, by certain characteristics of active people, said Steven Moore, an investigator at the National Cancer Institute who led the study.

“People who exercise generally go in for more checkups” than sedentary people, he said, resulting in more screenings for conditions such as so-called indolent prostate cancers. (There was no discernible association, positive or negative, between exercise and aggressive prostate tumors.) “They also often exercise outside,” he continued, “and are more prone to sunburns” than people who rarely work out, potentially contributing to a greater risk for melanoma.

Encouragingly, the associations between exercise and reduced cancer risks held true even when the researchers factored in body mass. People who were overweight or obese but exercised had a much lower risk of developing most cancers than overweight people who did not move much.

Just how physical activity may be undercutting the risk for so many disparate types of cancers is not yet fully understood, Dr. Moore said, although he and his colleagues suspect that changes in exercisers’ hormone levels, degree of inflammation, digestion and overall energy balance most likely contribute.

Bear in mind, though, that this was an observational study, so it cannot directly prove that exercise reduces cancer risks, only that there is an association between more exercise and less disease. It also relied on participants’ memories of exercise, which can be unreliable.

But even with those limitations, the findings sturdily suggest that exercise may help to reduce the risk of many types of cancer, “and it has few side effects and doesn’t cost much,” said Dr. Moore, who runs almost every day.

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Can High-Intensity Exercise Help Me Lose Weight? And Other Questions, Answered

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I recently wrote about a study showing that one minute of intense interval training, tucked into a workout that was, in total, 10 minutes long, produced comparable health and fitness benefits to 45 minutes of more moderate, uninterrupted endurance training.

Readers posted almost 400 comments to the article and flooded the Internet and my inbox with questions and sentiments about extremely short workouts. Given the extent of the response and the astuteness of the questions, I thought I would address some of the issues that arose over and over.

Q. Are high-intensity interval workouts actually better for you than longer, endurance-style workouts — or just shorter?

A. Better is such a subjective word. At the moment, the two types of workouts appear to be largely equivalent to each other in terms of a wide variety of health and fitness benefits.

In the study that I wrote about, “1 Minute of All-Out Exercise May Equal 45 Minutes of Moderate Exertion,” for instance, three months of high-intensity interval training practiced three times per week led to approximately the same improvements in aerobic endurance, insulin resistance and muscular health as far longer sessions of moderate pedaling on a stationary bicycle.

One type of workout was not more beneficial than the other, in other words, but one required much, much less time.

Other studies have generally produced similar results, although, to be honest, the science related to interval training for health purposes and not simply for athletic performance remains scant. An interesting new review of past research to be published in June did conclude that, for overweight and obese children, short sessions of intense intervals may lead to greater improvements in endurance and blood pressure than longer bouts of moderate exercise, although the authors did not discuss how best to get children to complete frequent interval sessions.

The upshot of the available science is that if you currently have the time and inclination to complete long-ish, moderate workouts — if you enjoy running, cycling, swimming, walking or rowing for 30 minutes or more, for instance — by all means, continue.

If, on the other hand, you frequently skip workouts because you feel that you do not have enough time to exercise, then very brief, high-intensity intervals may be ideal for you. They can robustly improve health and fitness without overcrowding schedules.

Q.

What about combining brief high-intensity workouts with longer, endurance workouts?

A.

Alternating high-intensity workouts with endurance-style workouts may yield the greatest health and fitness gains of all.

In a 2014 study, a group of sedentary adults began either a standard endurance-training program, in which they pedaled a bicycle moderately for 30 minutes five times a week, or swapped one of those bike rides for an interval session. All of the participants wound up significantly more aerobically fit after 12 weeks.

But the men and women who had completed one interval session per week had developed slightly more overall endurance than the other volunteers. As a result, they had lowered their risk for premature death by about an additional 18 percent, the study’s authors conclude.

Q.

Do I have to use a stationary bicycle for interval training?

A.

Most recent studies of high-intensity intervals have involved computerized stationary bicycles because scientists can easily monitor the riders’ pace and intensity. But there is nothing magical about the equipment. The key to high-intensity interval training is the intensity, which most of us can gauge either with a heart rate monitor or our own honest judgment.

For moderate exercise, your heart rate typically should be between 70 and 85 percent of your maximum. (I recently wrote about how to determine your individual maximum heart rate.) This intensity would feel like about an 8 on an arduousness scale of 1 to 10.

During an intense interval, however, your heart rate should rise to 90 percent of your maximum heart rate, or above. Think of this as feeling like about a 9.5 on the 10-point scale. You maintain that intensity for only 10 or 20 seconds at a time, however, followed by several minutes of very easy exercise before repeating the intense work.

Almost any type of exercise can be used for interval training, including running up the stairs in your office’s stairwell during your lunch hour, said Martin Gibala, a professor of kinesiology at McMaster University in Hamilton, Ontario, and an expert on intervals. (His book about the science and practical implications of high-intensity interval training will be published in early 2017.)

Q.

Will high-intensity intervals help me to lose weight?

A.

Few studies have yet looked at the long-term effects on body weight of exercising exclusively with high-intensity intervals, although some experiments do hint that high-intensity interval training can reduce body fat, at least in the short term.

In a 2015 study, for example, overweight, out-of-shape men who began either to jog or otherwise exercise moderately for an hour five days per week for six weeks or to complete intensive interval training for a few minutes per week all dropped body fat and about the same percentages of fat, despite very different amounts of exercise. Likewise, a group of women recovering from breast cancer who were assigned either to moderate exercise or brief interval training for three weeks lost comparable amounts of body fat during the study.

But these were small-scale, brief experiments. Whether interval training helps or hinders long-term weight control is still unknown.

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To Keep Obesity at Bay, Exercise May Trump Diet

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Young rats prone to obesity are much less likely to fulfill that unhappy destiny if they run during adolescence than if they do not, according to a provocative new animal study of exercise and weight. They also were metabolically healthier, and had different gut microbes, than rats that keep the weight off by cutting back on food, the study found. The experiment was done in rodents, not people, but it does raise interesting questions about just what role exercise may play in keeping obesity at bay.

For some time, many scientists, dieting gurus and I have been pointing out that exercise by itself tends to be ineffective for weight loss. Study after study has found that if overweight people start working out but do not also reduce their caloric intake, they shed little if any poundage and may gain weight.

The problem, most scientists agree, is that exercise increases appetite, especially in people who are overweight, and also can cause compensatory inactivity, meaning that people move less over all on days when they exercise. Consequently, they wind up burning fewer daily calories, while also eating more. You do the math.

But those discouraging studies involved weight loss. There has been much less examination of whether exercise might help to prevent weight gain in the first place and, if it does, how it compares to calorie restriction for that purpose.

So for the new study, which was published last week in Medicine & Science in Sports & Exercise, researchers at the University of Missouri in Columbia and other schools first gathered rats from a strain that has an inborn tendency to become obese, starting in adolescence. (Adolescence is also when many young people begin to add weight.)

These rats were young enough, though, that they were not yet overweight.

After weighing them, the researchers divided the animals into three groups.

One group was allowed to eat as much kibble as they wished and to remain sedentary in their cages. These were the controls.

Another group, the exercise group, also was able to eat at will, but these animals were provided with running wheels in their cages. Rats like to run, and the animals willingly hopped on the wheels, exercising every day.

The final group, the dieting group, was put on a calorie-restricted meal plan. Their daily kibble helpings were about 20 percent smaller than the amount that the runners ate, a portion size designed to keep them at about the same weight as the runners, so that extreme differences in body size would not affect the final results.

After 11 weeks, all of the animals were moved to specialized cages that could measure their metabolisms and how much they moved around. They then returned to their assigned cages for several more weeks, by which time they were effectively middle-aged.

At that point, the control animals were obese, their physiques larded with fat.

The runners and the lower-calorie groups, however, although they also had gained ounces, had put on far less weight than the controls. None were obese.

Both exercise and portion control, in other words, had effectively protected the animals against their fated fatness.

But beneath the skin, the runners and the dieters looked very unalike. By almost all measures, the runners were metabolically healthier, with better insulin sensitivity and lower levels of bad cholesterol than the dieters. They also burned more fat each day for fuel, according to their metabolic readings, and had more cellular markers related to metabolic activity within their brown fat than the dieting group. Brown fat, unlike the white variety, can be quite metabolically active, helping the body to burn additional calories.

Interestingly, the runners also had developed different gut microbes than the dieters, even though they ate the same food. The runners had greater percentages of some bacteria and smaller populations of others than the dieters or the control group; these particular proportions of gut bugs have been associated in a few previous studies with long-term leanness in both animals and people.

Perhaps most striking, “the runners showed no signs of compensatory eating or compensatory inactivity,” said Victoria Vieira-Potter, an assistant professor of nutrition and exercise physiology at the University of Missouri who oversaw the study. They didn’t scarf down more food than the control group, despite running several miles every day and, according to the specialized cages, actually moved around more when not exercising than either of the other groups of rats.

In essence, the runners, while weighing the same as the dieters at the end of the study, seemed better set up to avoid weight gain in the future.

Of course, these were rats, which do not share our human biology or our tangled psychological relationships with food and body fat.

This study also involved young, normal-weight rodents and cannot tell us whether exercise or dieting alone or in combination would aid or hinder weight loss in people (or animals) who already are overweight, Dr. Vieira-Potter said. Metabolisms change once a body contains large amounts of fat, and it becomes increasingly difficult to permanently drop those extra pounds.

So better to avoid weight gain in the first place, if possible. And in that context, she said, “restricting calories can be effective,” but exercise is likely to be more potent in the long term and, of course, as common sense would tell us, doing both—watching what you eat and exercising—is best of all.

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1 Minute of All-Out Exercise May Equal 45 Minutes of Moderate Exertion

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For many of us, the most pressing question about exercise is: How little can I get away with? The answer, according to a sophisticated new study of interval training, may be very, very little. In this new experiment, in fact, 60 seconds of strenuous exertion proved to be as successful at improving health and fitness as three-quarters of an hour of moderate exercise.

Let me repeat that finding: One minute of arduous exercise was comparable in its physiological effects to 45 minutes of gentler sweating.

I have been writing for some time about the potential benefits of high-intensity interval training, a type of workout that consists of an extremely draining but brief burst of exercise — essentially, a sprint — followed by light exercise such as jogging or resting, then another sprint, more rest, and so on.

Athletes rely on intervals to improve their speed and power, but generally as part of a broader, weekly training program that also includes prolonged, less-intense workouts, such as long runs.

But in the past few years, exercise scientists and many of the rest of us have become intrigued by the idea of exercising exclusively with intervals, ditching long workouts altogether.

The allure of this approach is obvious. Interval sessions can be short, making them a boon for anyone who feels that he or she never has enough time to exercise.

Previously, I have written about a number of different interval programs, involving anywhere from 10 minutes of exhausting intervals in a single session to seven minutes, six, four and even fewer. Each program had scientific backing. But because of time and funding constraints, most studies of interval training have had limits, such as not including a control group, being of short duration or studying only health or fitness results, not both.

Consequently, fundamental questions have remained unanswered about just how well these very short, very intense workouts really stack up against traditional, endurance-style training.

So scientists at McMaster University in Hamilton, Ontario, who had themselves conducted many of those earlier studies of interval training, decided recently to mount probably the most scientifically rigorous comparison to date of super-short and more-standard workouts.

They began by recruiting 25 out-of-shape young men and measuring their current aerobic fitness and, as a marker of general health, their body’s ability to use insulin properly to regulate blood sugar levels. The scientists also biopsied the men’s muscles to examine how well their muscles functioned at a cellular level.

Then the researchers randomly divided the men into three groups. (The scientists plan to study women in subsequent experiments.) One group was asked to change nothing about their current, virtually nonexistent exercise routines; they would be the controls.

A second group began a typical endurance-workout routine, consisting of riding at a moderate pace on a stationary bicycle at the lab for 45 minutes, with a two-minute warm-up and three-minute cool down.

The final group was assigned to interval training, using the most abbreviated workout yet to have shown benefits. Specifically, the volunteers warmed up for two minutes on stationary bicycles, then pedaled as hard as possible for 20 seconds; rode at a very slow pace for two minutes, sprinted all-out again for 20 seconds; recovered with slow riding for another two minutes; pedaled all-out for a final 20 seconds; then cooled down for three minutes. The entire workout lasted 10 minutes, with only one minute of that time being strenuous.

Both groups of exercising volunteers completed three sessions each week for 12 weeks, a period of time that is about twice as long as in most past studies of interval training.

By the end of the study, published in PLOS One, the endurance group had ridden for 27 hours, while the interval group had ridden for six hours, with only 36 minutes of that time being strenuous.

But when the scientists retested the men’s aerobic fitness, muscles and blood-sugar control now, they found that the exercisers showed virtually identical gains, whether they had completed the long endurance workouts or the short, grueling intervals. In both groups, endurance had increased by nearly 20 percent, insulin resistance likewise had improved significantly, and there were significant increases in the number and function of certain microscopic structures in the men’s muscles that are related to energy production and oxygen consumption.

There were no changes in health or fitness evident in the control group.

The upshot of these results is that three months of concerted endurance or interval exercise can notably — and almost identically — improve someone’s fitness and health.

Neither approach to exercise was, however, superior to the other, except that one was shorter — much, much shorter.

Is that reason enough for people who currently exercise moderately or not at all to begin interval training as their only workout?

“It depends on who you are and why you exercise,” said Martin Gibala, a professor of kinesiology at McMaster University who oversaw the new study.

“If you are an elite athlete, then obviously incorporating both endurance and interval training into an overall program maximizes performance. But if you are someone, like me, who just wants to boost health and fitness and you don’t have 45 minutes or an hour to work out, our data show that you can get big benefits from even a single minute of intense exercise.”

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Getting People to Move More

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In 2010, a group of public and private organizations banded together to develop and release the first National Physical Activity Plan, a blueprint for getting Americans to move more.

Among its recommendations were that every schoolchild be allowed and encouraged to participate in frequent — and preferably daily — physical education classes; that employers find ways to reduce sitting time at the office; and that municipalities both create and promote parklands, bike paths and other places for people to be active.

But since the release of the plan, by an alliance that includes the American Heart Association, American Cancer Society, Centers for Disease Control and Prevention, and the Department of Health and Human Services, physical activity levels in the United States have barely budged, and for many people, they have declined. According to a recent report, only eight states require recess every day for elementary school students and only Oregon and the District of Columbia mandate that all children in elementary and middle school participate in at least 30 minutes of physical education every day, the minimum desirable level of daily P.E. that experts recommend.

Meanwhile, according to the C.D.C., barely 20 percent of American adults meet the minimum national exercise guidelines of at least 150 minutes per week of mixed aerobic workouts and strength training. The percentages are even lower for many minority groups, including Hispanic adults. Only about 15 percent of them manage to meet the exercise recommendations.

More disquieting, a health study published last month concluded that, over all, fewer than 3 percent of American adults live the kind of comprehensively healthy life that we all know we should, with a diet rich in fruits and vegetables, no smoking, a normal weight and regular exercise. Of these, the factor that was most likely to keep someone from joining the small group of health-wise Americans was exercise. Almost no one in the study did much.

In the face of this seemingly intractable tug toward physical stillness, the alliance today released a new National Physical Activity Plan, with updated priorities, a broader focus on minorities with the addition of a diversity committee, and more recommendations and advice for how people might encourage physical activity in their communities and schools.

To find out more about the new plan and why so many of us remain so resolutely sedentary, I spoke with Russell Pate, a professor of public health at the University of South Carolina in Columbia and chairman of the National Physical Activity Plan Alliance. Here are edited excerpts from our conversation.

Q.

The most obvious question about the National Physical Activity Plan is why do we need one? Why is it still so hard to get people to exercise, when we all know that we should?

A.

In fairness to people, we have made it so easy to be inactive. Once, stairs would have been the first thing that you saw in a building. Today, elevators are front and center. You have to hunt around for the stairs. And we can drive everywhere. In today’s world, it’s activity that is unusual, not inactivity. Being active requires commitment, and for some people, that commitment can seem too much. A single mother of three kids working two or three jobs may well feel like working out is a luxury that she can do without.

Q.

Is that why the plan emphasizes physical activity rather than exercise?

A.

Many people think of exercise as something that is planned and high-intensity and a lot of work. Physical activity is a more inclusive term. Any movement can be considered physically active and beneficial, even if you just walk around the house instead of sitting on the couch. We want to convey the idea that you don’t have to exercise, just move more.

Q.

But how, in a concrete way, can a national plan increase activity? How could someone use the plan to, for instance, get more P.E. classes added to the curriculum of their child’s elementary school?

A.

There is a section devoted to education. It includes a series of evidence-based strategies and tactics. You can find information there about why schools should meet national and state standards for physical education and how to accomplish that, such as encouraging shared-use agreements so that schools can use community facilities if they don’t have their own resources. This plan is meant to be practical. A parent could print out that section, take it to a school board meeting and say, ‘Look, I didn’t dream up the idea that we need P.E. It’s right here in the National Physical Activity Plan.’

Q.

Are you optimistic?

A.

We are swimming upstream. We know that. The social conditions that promote inactivity have been building for decades. It is so easy now not to move. But the consequences are also becoming more obvious. Inactivity is associated with so many health problems and premature death. I believe that as people consider what it means to have a high-quality life, there will be a shift in behavior. Do we want to spend our lives on the couch surrounded by empty pizza boxes? Sure, some people might. But I think that most of us want healthy workplaces, schools and homes. We want our children and loved ones and ourselves to be well. To achieve that, we must move more.

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An Easy Way to Prevent Blisters? Try Tape

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Credit Getty Images

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Paper tape, the kind you can find in a first-aid kit, can help prevent blisters.

Paper tape, the kind you can find in a first-aid kit, can help prevent blisters.Credit Grant S. Lipman, M.D.

Exercise science today is exploring countless mysterious, exciting and poetic aspects of human physiology and performance. But sometimes you just wish that someone would tell you how to keep your feet from hurting. A wonderfully practical new study obliges, providing the first reliable, field-tested evidence about how to prevent blisters during prolonged exercise. Anyone running next week’s Boston Marathon, you’re welcome.

Blisters are one of the most common bugaboos of physical activity. Almost everyone who regularly trains or competes in any sport has experienced blisters. They reportedly afflict about 40 percent or more of marathon runners and frequently cause racers to drop out of the event.

“Blisters happen to just about everyone,” said Dr. Grant S. Lipman, a clinical associate professor of medicine at Stanford University, who led the new study.

Blisters develop when something rubs repeatedly against a patch of skin. The resulting friction causes the top layers of the skin to begin separating from one another, producing a feeling of heat. This is a hot spot, a warning sign of an incipient blister. If the friction continues, fluid fills the spaces between the skin layers, and you have a blister.

Blisters hurt, as most of us know from experience. So active people have tried many methods to avoid them. Past studies in the small field of blister science have found that, by and large, none of these methods work. Applying petroleum jelly to the feet, for instance, increases friction and the incidence of blisters, according to a 1995 study. Ditto for wearing cotton socks, using lotion combined with antiperspirant, or sticking a bandage, Moleskin or other specialized protective patch onto the foot.

But Dr. Lipman, who is the director of the Wilderness Medicine program at Stanford and the medical director for several ultramarathons around the world, had heard from ultramarathon runners that wrapping parts of their feet in paper tape helped them to stave off blisters.

Paper tape is exactly what its name suggests, a thin, inexpensive tape made of paper. You can find it at virtually any drugstore, sold as surgical or medical tape, and it is a common component of first-aid kits. It is thinner than bandages, and breathable.

But anecdotes from happy racers do not constitute scientific evidence, Dr. Lipman knew.

So for the new study, which was published this week in the Clinical Journal of Sport Medicine, he turned to a group for whom blisters are almost inevitable: ultra-ultramarathoners and, specifically, the participants in an annual, grueling multistage ultramarathon run across parts of Jordan, Madagascar and the Gobi and Atacama deserts.

Dr. Lipman and his colleagues asked all of the runners signed up for the 2014 event if they would wear paper tape on their feet to determine if doing so actually prevented blisters. Almost 130 men and women agreed.

Immediately before the first stage began, those racers visited Dr. Lipman’s medical tent and had their feet wrapped. Runners with a history of blisters, which was most of the runners, showed the researchers where they had been prone to develop the sores in the past. Those areas — usually the toes — were then covered with the thin tape. If someone had not experienced blisters before, the researchers wrapped parts of their feet at random.

The uncovered portions of each runner’s affected foot would serve as a control, the scientists had decided. If a runner developed no blisters or blisters only where his or her foot had remained unprotected, then the tape could be considered to have worked.

Six stages and more than 200 miles later, most of the runners had developed at least one blister. But an overwhelming majority of those blisters, about 70 percent, had occurred on the unprotected parts of the foot. Very few blisters had developed beneath the tape.

Over all, the scientists concluded, the tape had reduced the incidence of blisters by at least 40 percent, a very “robust effect,” they wrote.

But there were quibbles. Paper tape is not very sticky and typically will peel away as feet sweat. Most runners had to reapply the tape multiple times throughout the race stages, meaning they had to carry a roll with them, stop, uncover their feet, retape and resume running. Whether participants in shorter, single-stage events, such as a marathon, would need to retape their feet is not known

(On the plus side, Dr. Lipman said, paper tape won’t stick to a blister and tear away skin or tissue when removed, as bandages will.)

Most of the racers involved in the study, however, said afterward that they planned to use the tape in future events, Dr. Lipman said.

For those at home considering likewise taping their feet to avoid blisters, the process is simple, he said. Cut or tear a single narrow strip of the paper tape and wrap it over whichever part of your foot has been prone to blisters. (See photo.) For most people, the toes and ankle are the spots most vulnerable to blisters.

Also, he said, use common sense. Make sure that your shoes fit and don’t rub against your skin. Never wear brand-new shoes in a race, as you won’t know whether they rub. And don’t wear cotton socks or coat your feet in petroleum jelly.

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Does Exercise During Pregnancy Lead to Exercise-Loving Offspring?

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Mice born to mothers that run during their pregnancies grow up to be rodents that love to run as adults, according to a thought-provoking new animal experiment, while pups with sedentary moms had a less-enthusiastic attitude toward exercise. Though it’s a long way from mice to people, the study’s findings hint at the possibility that to some extent our will to work out may be influenced by a mother’s exercise habits during pregnancy, and begin as early as in the womb.

Most of us have probably observed that activity patterns tend to run in families, a situation that has been confirmed in studies involving both people and animals. Children whose parents are sedentary often tend to be inactive themselves, whereas parents who are physically active typically have children who move around and exercise often.

Logically, home environment and nurture influence familial activity levels; children learn from and mimic their parents.

Recent science, however, suggests that there are other, deeper biological influences at work as well, including genetics. A number of studies have identified various snippets of DNA that, if someone carries them, predispose that person to be quite active, while other gene variations may nudge someone toward being a couch potato.

But scientists also have begun to wonder about the role of a process known as developmental programming. According to this theory, a growing baby’s body and its very DNA can be changed by the environment it experiences in the womb and immediately after birth. These changes may, in turn, affect lifelong health and disease risk. Mouse pups born to mothers that become overweight and metabolically unhealthy during pregnancy, for instance, are more likely to be overweight and diabetic as adults than genetically identical mice born to mothers that maintain a normal weight during pregnancy.

To what extent developmental programming might affect someone’s willingness to work out, though, had rarely been explored.

So for the new study, which was published this month in the FASEB Journal, researchers from Baylor University and Rice University in Houston gathered genetically identical female mice and put them in cages with running wheels. Mice like running, and most of these animals jogged about six miles a day. After a week with wheels, the females were matched with male mice from the same genetic line. Pregnancies ensued.

At that point, half of the pregnant mice had their running wheels locked so that they could not run freely during pregnancy.

The other mice were allowed to continue running at will throughout their pregnancies, and they did keep running, although their distance and speed declined as they grew heavy with young.

After the babies were born and weaned, the pups were removed to their own cages, without wheels. Their cages were separated from those of the adult mice, so the young mice would not have watched their mothers working out and tried to emulate them.

But at multiple points throughout their lives, this second generation of mice was moved for several days to special cages equipped with unlocked running wheels and monitors that tracked how much they moved when not on the wheels.

During the pups’ childhoods, the scientists noted few differences in exercise behavior between the young mice. But as the animals entered adolescence, those born to running moms started to become enthusiastic runners themselves, putting in more miles on the wheels than the other mice and moving around more frequently in their cages when they were not running.

These differences accelerated as the animals aged, so that during the rodent equivalent of middle age, the animals born to runners were running and moving around significantly more throughout the day than the other mice, even though all of them were genetically the same and had had identical upbringings.

The clear implication of these results is that “a mother’s physical activity during pregnancy likely affects the physical activity of her offspring,” said Robert Waterland, a professor of pediatrics and genetics at Baylor who led with study with his colleagues Jesse Eclarinal and Shaoyu Zhu.

In essence, baby mice with active moms had literally been born to run.

Of course, mice are not people, and this study can’t tell us whether similar programming occurs in our babies if we are active during pregnancy.

The study also can’t explain how exercise during pregnancy affects a developing infant’s later urge to work out. It may be, Dr. Waterman said, that the mother’s physical movements jiggle the womb slightly in ways that alter fetal brain development in parts of the brain devoted to motor control and behavior; or that certain biochemicals produced by the mom during exercise pass through the placenta, affecting the baby’s physiology and gene activity lifelong.

He and his colleagues hope to study those issues in future experiments.

But for now, he said, it’s important that no mother interpret these results as a criticism if she didn’t exercise much during pregnancy. Those of us who have borne children know how exhausting the experience can be. But, he said, if a pregnant woman — with her doctor’s blessings — can walk, jog, swim or otherwise be physically active, she may improve her own health and also, just possibly, instill an incipient love of exercise in the child growing within her.

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Exercise Makes Our Muscles Work Better With Age

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To keep our muscles healthy deep into retirement, we may need to start working out more now, according to a new study of world-class octogenarian athletes. The study found substantial differences at a cellular level between the athletes’ muscles and those of less active people.

Muscular health is, of course, essential for successful aging. As young adults, we generally have scads of robust muscle mass. But that situation doesn’t last.

Muscles consist of fibers, each attached to a motor neuron in our spinal column by long, skinny nerve threads called axons. The fiber and its neuron are known as a muscle unit.

When this muscle unit is intact, the neuron sends commands to the muscle fiber to contract. The muscle fiber responds, and your leg, eyelid, pinky finger or other body part moves.

However, motor neurons die as we age, beginning as early as in our 30s, abruptly marooning the attached muscle fiber, leaving it disconnected from the nervous system. In younger people, another neuron can come to the rescue, snaking out a new axon and re-attaching the fiber to the spinal cord

But with each passing decade, we have fewer motor neurons. So some muscle fibers, bereft of their original neuron, do not get another. These fibers wither and die and we lose muscle mass, becoming more frail. This process speeds up substantially once we reach age 60 or so.

Scientists have not known whether the decline in muscular health with age is inevitable or whether it might be slowed or altered.

There have been encouraging hints that exercise changes the trajectory of muscle aging. A 2010 study of recreational runners in their 60s, for instance, found that their leg muscles contained far more intact muscle units than the muscles of sedentary people of the same age.

But whether exercise would continue to protect muscles in people decades older than 60, for whom healthy muscles might be the difference between independence and institutionalization, had never been examined.

So for the new study, which was published last week in the Journal of Applied Physiology, researchers from McGill University in Canada and other schools contacted 29 world-class track and field athletes in their 80s and invited them to the university’s performance lab. They also recruited a separate group of healthy but relatively inactive people of the same age to act as controls.

At the lab, the scientists measured muscle size and then had the athletes and those in the control group complete a simple test of muscular strength and function in which they pressed their right foot against a movable platform as forcefully as possible. While they pressed, the scientists used sensors to track electrical activity within a leg muscle.

Using mathematical formulas involving muscle size and electrical activity, the scientists then determined precisely how many muscle units were alive and functioning in each volunteer’s leg muscle. They also examined the electrical signal plots to see how effectively each motor neuron was communicating with its attached muscle fiber.

Unsurprisingly, the elite masters athletes’ legs were much stronger than the legs of the other volunteers, by an average of about 25 percent. The athletes had about 14 percent more total muscle mass than the control group.

More interesting to the researchers, the athletes also had almost 30 percent more motor units in their leg muscle tissue, and these units were functioning better than those of people in the sedentary group. In the control group, many of the electrical messages from the motor neuron to the muscle showed signs of “jitter and jiggle,” which are actual scientific terms for signals that stutter and degrade before reaching the muscle fiber. Such weak signaling often indicates a motor neuron that is approaching death.

In essence, the sedentary elderly people had fewer motor units in their muscles, and more of the units that remained seemed to be feeling their age than in the athletes’ legs.

The athletes’ leg muscles were much healthier at the cellular level.

“They resembled the muscles of people decades younger,” said Geoffrey Power, who led the study while a graduate student at McGill and is now an assistant professor at the University of Guelph in Ontario.

Of course, this type of single-snapshot-in-time study can’t tell us whether the athletes’ training actually changed their muscle health over the years or if the athletes were somehow blessed from birth with better muscles, allowing them to become superb masters athletes.

But Dr. Power, who also led the 2010 study, said that he believes exercise does add to the numbers and improve the function of our muscle units as we grow older.

Whether we have to work out like a world-class 80-year-old athlete to benefit, however, remains in question. Most of these competitors train intensely for several hours every week, Dr. Power said. But on the plus side, some of them did not start their competitive regimens until they had reached their 50s, providing hope for the dilatory among us.

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Chocolate Can Boost Your Workout. Really.

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Adding a little dark chocolate to a training diet may effortlessly improve endurance performance, according to a new study of sports nutrition. The findings provide ammunition both for athletes looking for an edge and those hoping for an excuse to indulge.

For some time, dark chocolate has been touted as a relatively healthy treat, with studies showing that small amounts may have benefits for the heart and brain. Most of this research has focused on the role of a substance called epicatechin, a plant nutrient found in cocoa. Dark chocolate is generally rich in epicatechin, though levels vary, depending on how the sweet was produced. Levels of epicatechin tend to be much lower in milk chocolate, which contains little cocoa, and white chocolate contains little or none of the nutrient.

Epicatechin is known to prompt cells that line blood vessels to release extra nitric oxide, a substance that has multiple effects in the body. Nitric oxide slightly increases vasodilation, or a widening of the veins and arteries, improving blood flow and cardiac function. It also gooses muscle cells to take in more blood sugar, providing them with more energy, and it enhances the passage of oxygen into cells.

Because of its many physiological effects, each of which can aid physical performance, athletes long have looked for ways to increase the amount of nitric oxide in their bloodstreams. Some down supplement pills, although the benefits of nitric oxide supplements are unproven. Others swallow beetroot juice, a beverage that contains a hefty dose of nitrates, which then break down in the body into nitric oxide and other substances. There are questions, however, about the safety of nitrates and also, as anyone who has tried beetroot juice will tell you, the palatability of a beverage that tastes distinctly like liquid dirt.

Surprisingly, athletes and scientists have devoted relatively little attention to the potential of dark chocolate as a way to up natural nitric oxide and subsequent performance, perhaps in part because chocolate can cause weight gain and also seems neither medicinal nor unpleasant, two attributes often associated with ergogenic aids.

But researchers at Kingston University in England suspected that dark chocolate might be a potent performance enhancer, if the chocolate were deployed carefully.

So for the new study, which was published in December in The Journal of the International Society of Sports Medicine, they found eight male recreational cyclists who agreed, in the interests of science, to swallow a little dark chocolate every day.

The cyclists first, however, visited the researchers’ lab for tests of their fitness and oxygen uptake during moderate rides and all-out sprints on a stationary bicycle.

Then the scientists provided half of the cyclists with 40 grams (1.4 ounces, or about one and a half squares) per day of Dove brand dark chocolate, which has been found in past tests to contain an above-average amount of epicatechin.

The cyclists were told to replace one of their normal snacks or desserts with the chocolate, to avoid weight gain.

The other cyclists were provided with 40 ounces of white chocolate, as a control.

They all ate their chocolate every day for two weeks, then returned to the lab to repeat the tests.

Then each group was provided with whichever type of chocolate, white or dark, they had not eaten before and sent off for another two weeks.

They returned and repeated the cycling and oxygen uptake tests again.

The results were beguiling. Each of the cyclists performed better in most of the physical tests after two weeks of supplementing with dark chocolate, compared to baseline results and after they had eaten white chocolate. The riders utilized less oxygen to ride at a moderate pace, a change that would generally allow them to ride longer or harder before tiring; and they covered more distance during a two-minute, all-out time trial, meaning that their anaerobic, sprinting ability had been enhanced.

The researchers did not directly measure nitric oxide in their volunteers’ blood, but believe that the chocolate ramped up production of the substance, improving oxygen delivery to riders’ cells.

Performance gains were not huge. The riders who had eaten dark chocolate covered an additional tenth of a mile during the two-minute time trial compared to when they had white chocolate. But that extra mileage occurred, the scientists point out, even though the riders otherwise followed the same dietary and training regimens during each of the two-week sessions.

The upshot of these findings would seem to be that “recreational athletes who would like to improve their performance” might consider swapping a daily cookie or soda for a square or two of dark chocolate, said Rishikesh Kankesh Patel, a graduate student at Kingston University who led the study.

But he cautioned that scientists do not yet know the ideal dosage of dark chocolate for athletes, and that more than 40 grams is unlikely to be helpful, so put away the rest of that bar. Cocoa and epicatechin levels also vary widely from bar to bar, he said, which makes precise dosing of the performance-enhancing content tricky.

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Meditation Plus Running as a Treatment for Depression

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Meditating before running could change the brain in ways that are more beneficial for mental health than practicing either of those activities alone, according to an interesting study of a new treatment program for people with depression.

As many people know from experience, depression is characterized in part by an inability to stop dwelling on gloomy thoughts and unhappy memories from the past. Researchers suspect that this thinking pattern, known as rumination, may involve two areas of the brain in particular: the prefrontal cortex, a part of the brain that helps to control attention and focus, and the hippocampus, which is critical for learning and memory. In some studies, people with severe depression have been found to have a smaller hippocampus than people who are not depressed.

Interestingly, meditation and exercise affect those same portions of the brain, although in varying ways. In brain-scan studies, people who are long-term meditators, for instance, generally display different patterns of brain-cell communication in their prefrontal cortex during cognitive tests than people who don’t meditate. Those differences are believed to indicate that the meditators possess a more honed ability to focus and concentrate.

Meanwhile, according to animal studies, aerobic exercise substantially increases the production of new brain cells in the hippocampus.

Both meditation and exercise also have proven beneficial in the treatment of anxiety, depression and other mood disorders.

These various findings about exercise and meditation intrigued researchers at Rutgers University in New Brunswick, N.J., who began to wonder whether, since meditation and exercise on their own improve moods, combining the two might intensify the impacts of each.

So, for the new study, which was published last month in Translational Psychiatry, the scientists recruited 52 men and women, 22 of whom had been given diagnoses of depression. The researchers confirmed that diagnosis with their own tests and then asked all of the volunteers to complete a computerized test of their ability to focus while sensors measured electrical signals in their brains.

The researchers found that the depressed volunteers showed signaling patterns in their prefrontal cortex that are associated with poor concentration and focus.

Then the researchers had all of the volunteers begin a fairly rigorous, supervised program of sitting, followed by sweating.

To start, the volunteers were taught a form of meditation known as focused attention. Essentially entry-level mindfulness meditation, it requires people to sit quietly and think about their respiration by counting their breaths up to 10 and then backward. This practice is not easy, especially at first.

“If people found their thoughts wandering” during the meditation, and especially if they began to ruminate on unpleasant memories, they were told not to worry or judge themselves, “but just to start counting again from one,” said Brandon Alderman, a professor of exercise science at Rutgers who led the study.

The volunteers meditated in this way for 20 minutes, then stood and undertook 10 minutes of walking meditation, in which they paid close attention to each footfall.

Then they clambered onto treadmills or stationary bicycles at the lab and jogged or pedaled at a moderate pace for 30 minutes (with five minutes of warming up and five minutes of cooling down).

The volunteers completed these sessions twice a week for eight weeks. Then the researchers retested their moods and their ability to focus and concentrate.

There were significant changes. The 22 volunteers with depression now had a 40 percent reduction in symptoms of the condition. They reported, in particular, much less inclination to ruminate over bad memories.

Meanwhile, the members of the healthy control group also reported feeling happier than they had at the start of the study.

Objectively, the volunteers’ results on the computerized tests of their ability to focus and their brain activity also were different. The group with depression now showed brain cell activity in their prefrontal cortex that was almost identical to that of the people without depression. They could concentrate much better and hone their attention, attributes that are believed to help reduce stubborn rumination.

“I was quite surprised that we saw such a robust effect after only eight weeks,” Dr. Alderman said.

He and his colleagues theorize that the meditation and exercise may have produced synergistic effects on the brains of their volunteers.

“We know from animal studies that effortful learning, such as is involved in learning how to meditate, encourages new neurons to mature” in the hippocampus, he said.

So while the exercise most likely increased the number of new brain cells in each volunteer’s hippocampus, Dr. Alderman said, the meditation may have helped to keep more of those neurons alive and functioning than if people had not meditated.

Meditation also may have made the exercise more tolerable, he said, since some studies indicate that being mindful of your breathing and your body during workouts increases people’s enjoyment of the exertion.

“I’ve started meditating,” said Dr. Alderman, a long-time athlete.

Of course, this was a small study and the scientists did not follow their volunteers long term, so they do not know if any mood improvements linger. They also have no idea whether similar or even greater benefits might occur if someone were to run and then meditate or to practice both activities but on alternating days. They plan to study those questions in future experiments.

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For Serious Training, Hold the Carbs at Dinnertime

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Triathletes plunged into the Hudson River for the 12th annual N.Y.C. Triathlon held in 2012.

Triathletes plunged into the Hudson River for the 12th annual N.Y.C. Triathlon held in 2012.Credit Christopher Gregory for The New York Times

Strategically skipping bread, pasta and other carbohydrates at dinner might improve subsequent athletic performance, provided those low-carb meals are combined with the right types of workouts, according to a new sports nutrition study. Its findings undercut some entrenched ideas about how athletes should eat in preparation for spring marathons and other endurance races.

As those of us who are athletes or spend time around them know, diets are a topic of consuming interest for the group, since an athlete’s diet affects how well he or she can train, recover, progress, chisel a physique and compete.

But the ideal sports diet remains elusive. Many dietitians and coaches advocate for heaps of carbohydrates at the training table. Carbohydrates, which break down during digestion into sugar, are the body’s first choice as fuel during exercise. But the body’s reservoir of stored carbohydrates is small, and even if athletes supplement their supply during exercise with sugary drinks or food, prolonged or intense exertion generally incinerates much of the body’s available carbohydrates.

Consequently, some experts suggest that athletic success may depend in part on making the body better able to use fat as a fuel. Even the leanest athlete’s body is girded with the stuff, theoretically providing enough energy for even the longest, hardest workouts. Low-carbohydrate diets will force the body to turn to fat. But working muscles must become used to burning fat, a process that can make exercising on a low-carb diet difficult in the short term. Indeed, athletes on extremely low-carbohydrate diets tend to struggle to finish hard workouts.

So researchers at the French National Institute of Sport, Expertise and Performance in Paris and other institutions began to wonder about the possibilities of modified forms of low-carb diets, and specifically about what they and other scientists call “sleeping low.”

With a “sleep-low” sports diet, an athlete skips carbohydrates at dinner. In the morning, his or her body should have low reserves of the macronutrient, and any ensuing workouts would force the body to turn to fat, its most abundant fuel. In past studies of the technique, however, it has produced mixed results in terms of whether it improves competitive performance.

The authors of the new study, which was published in January in Medicine & Science in Sports & Exercise, suspected that the sleep-low diet needed to be integrated into a broader training plan in order to show desirable results.

To test that possibility, they recruited 21 experienced, competitive triathletes who bravely agreed to have their diets manipulated. The scientists ran their volunteers through a simulated triathlon and other tests of their current fitness and pace.

Half of the athletes were then randomly assigned to eat a standard sports diet, with large helpings of carbohydrates at every meal and after workouts.

The others were put on a sleep-low regimen. With this program, the athletes consumed the same amount of carbohydrates over the course of the day as the other group, but in a different sequence. Virtually all of their carbohydrates were consumed at breakfast and lunch, with none at dinner.

At the same time, all of the athletes also began a new training program. In the afternoon, both groups completed a draining, intense interval-training session, designed to increase fitness and deplete the body’s carbohydrate stores. The members of the control group then replenished their carbohydrates at dinner; the sleep-low group did not.

Next morning, before breakfast, the volunteers pedaled for an hour at a moderate pace on stationary bicycles. By this time, the sleep-low group was running on carbohydrate fumes and body fat.

Afterward, all of the athletes sat down to large, carb-rich breakfasts and lunches, meaning that both groups were flush with carbohydrates for the afternoon interval training.

This program continued for four days per week for three weeks. (On the remaining days, the athletes ran, cycled or swam at an easy pace and ate as they chose.)

After three weeks, the athletes in the sleep-low group were grumbling about evening hunger.

But when the researchers now repeated the simulated triathlon, those athletes in the sleep-low group showed notable improvement. Their times on the 10-kilometer running leg at the end of the race were faster by about 75 seconds, or 3 percent, than at the start of the study. The control group had not improved.

The sleep-low volunteers also had lost body fat, while the other athletes had not.

These findings suggest, said Laurie-Anne Marquet, a graduate student at the French National Institute of Sport who led the study, that exercising strenuously in the afternoon, depriving yourself of carbohydrates afterward, training gently the next morning and then swallowing a mound of pancakes might be a useful way to improve endurance and performance. The regimen seemed to have increased the athletes’ ability to access fat as muscle fuel, she said, allowing them to exercise harder during the workouts than the control group and gain additional fitness and speed.

Such a rigorous routine is not for everyone, of course. Those of us not training for a marathon, triathlon or similar event probably would not enjoy or benefit from sleeping low. Even serious athletes should thread the approach into their training cautiously, Ms. Marquet said, beginning a few weeks before a race and easing off in the days just before the event, when they should down carbohydrates at will.

Encouragingly for those tempted by the diet, though, “most of the athletes” in the study, Ms. Marquet said, “have now integrated this strategy into their training.”

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Learning a New Sport May Be Good for the Brain

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Gretchen Reynolds, Phys Ed columnist, tries snowboarding for the first time.

Gretchen Reynolds, Phys Ed columnist, tries snowboarding for the first time.Credit Lynn Tran

Learning in midlife to juggle, swim, ride a bicycle or, in my case, snowboard could change and strengthen the brain in ways that practicing other familiar pursuits such as crossword puzzles or marathon training will not, according to an accumulating body of research about the unique impacts of motor learning on the brain.

When most of us consider learning and intelligence, we think of activities such as adding numbers, remembering names, writing poetry, learning a new language.

Such complex thinking generally is classified as “higher-order” cognition and results in activity within certain portions of the brain and promotes plasticity, or physical changes, in those areas. There is strong evidence that learning a second language as an adult, for instance, results in increased white matter in the parts of the brain known to be involved in language processing.

Regular exercise likewise changes the brain, as I frequently have written, with studies in animals showing that running and other types of physical activities increase the number of new brain cells created in parts of the brain that are integral to memory and thinking.

But the impacts of learning on one of the most primal portions of the brain have been surprisingly underappreciated, both scientifically and outside the lab. Most of us pay little attention to our motor cortex, which controls how well we can move.

“We have a tendency to admire motor skills,” said Dr. John Krakauer, a professor of neurology and director of the Center for the Study of Motor Learning and Brain Repair at Johns Hopkins University in Baltimore. We like watching athletes in action, he said. But most of us make little effort to hone our motor skills in adulthood, and very few of us try to expand them by, for instance, learning a new sport.

We could be short-changing our brains.

Past neurological studies in people have shown that learning a new physical skill in adulthood, such as juggling, leads to increases in the volume of gray matter in parts of the brain related to movement control.

Even more compelling, a 2014 study with mice found that when the mice were introduced to a complicated type of running wheel, in which the rungs were irregularly spaced so that the animals had to learn a new, stutter-step type of running, their brains changed significantly. Learning to use these new wheels led to increased myelination of neurons in the animals’ motor cortexes. Myelination is the process by which parts of a brain cell are insulated, so that the messages between neurons can proceed more quickly and smoothly.

Scientists once believed that myelination in the brain occurs almost exclusively during infancy and childhood and then slows or halts altogether.

But the animals running on the oddball wheels showed notable increases in the myelination of the neurons in their motor cortex even though they were adults.

At the same time, other animals that simply ran on normal wheels for the same period of time showed no increase in myelination afterward.

In other words, learning the new skill had changed the inner workings of the adult animals’ motor cortexes; practicing a well-mastered one had not.

“We don’t know” whether comparable changes occur within the brains of grown people who take up a new sport or physical skill, Dr. Krakauer said. But it seems likely, he said. “Motor skills are as cognitively challenging” in their way as traditional brainteasers such as crossword puzzles or brain-training games, he said. So adding a new sport to your repertory should have salutary effects on your brain, and also, unlike computer-based games, provide all the physical benefits of exercise.

These considerations cheered me a few weeks ago when I took to the slopes of my local mountain for a weekend-long crash course in snowboarding. (Crashing, regrettably, is inevitable while learning to shred.) I had wondered if I might be too advanced in years and hardened in the habits of skiing to learn to ride. But the experience was in fact exhilarating and glorious. Learning a new sport or skill when you are old enough to be a parent to your instructor is psychologically uplifting, as well as beneficial for the body and brain. It reminds you that your body can still respond, that it can still yearn for movement and speed.

By the end of the second day, I attempted my first moguls on a snowboard and completed precisely one turn before auguring hindside into the slope and slipping and picking my way down the rest of the run. But one mogul turn was 100 percent more than I had managed before. I now aim to return to the mountain and double that number to two turns, which is how we learn and progress and, with luck, change our minds — both literally and about our limits.

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How Exercise May Lower Cancer Risk

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The relationship between exercise and cancer has long both intrigued and puzzled oncologists and exercise physiologists.

Exercise is strongly associated with lowered risks for many types of cancer. In epidemiological studies, people who regularly exercise generally prove to be much less likely to develop or die from the disease than people who do not. At the same time, exercise involves biological stress, which typically leads to a short-term increase in inflammation throughout the body. Inflammation can contribute to elevated risks for many cancers.

Now, a new study in mice may offer some clues into the exercise-cancer paradox. It suggests that exercise may change how the immune system deals with cancer by boosting adrenaline, certain immune cells and other chemicals that, together, can reduce the severity of cancer or fight it off altogether.

To try to better understand how exercise can both elevate inflammation and simultaneously protect the body against cancer, scientists at the University of Copenhagen in Denmark and other institutions decided to closely examine what happens inside mice at high risk for the disease.

So, for the new study, which was published this month in Cell Metabolism, they began by gathering a group of adult lab mice. These animals generally like to run.

The scientists then implanted melanoma skin cancer cells into the mice before providing half of them with running wheels in their cages while the other animals remained sedentary. After four weeks, far fewer of the runners had developed full-blown melanoma than the sedentary mice and those that had been diagnosed with the disease showed fewer and smaller lesions. They also were less prone to metastases, even if scientists injected some of the cancer cells into their lungs to stimulate metastases.

In effect, running seemed to have at least partially inoculated the mice against the cancer.

Next, the scientists undertook the far more challenging task of reverse-engineering the process by which exercise might be helping to fight off the tumors. To start, they drew blood from both the exercising and sedentary animals and cells from any tumors in both groups. Then they looked microscopically at how the various samples were different.

As expected, they found much higher levels of the hormone adrenaline in the blood of the exercising animals, especially right after they had been working out on the wheels but also at other times of the day. The body releases adrenaline in response to almost any type of stressful experience, including exercise.

They also found higher levels of interleukin-6 in the blood of the runners. This is a substance that is released by working muscles and is believed to both increase and decrease inflammation in the body capriciously, depending on where and how it goes to work.

Perhaps most important, they found much higher numbers in the bloodstreams of runners than in the sedentary mice of a type of immune cell named natural killer cells that are known to be potent cancer fighters.

Somehow, the scientists speculated, these elements in the runners — their elevated adrenaline, IL-6, and natural killer immune cells and their lower cancer risk — must be entwined, but it wasn’t clear how.

So the scientists repeated their original experiment multiple times, inducing cancer while allowing some mice to run and others to sit. But in some of these follow-up experiments, they injected the runners with a substance that blocked the production of adrenaline and gave sedentary animals large doses of added adrenaline.

Then they again looked at the animals’ blood and other cells.

What they now saw was that when running mice could not produce adrenaline, they developed cancer at the same rate as the sedentary animals, while the sedentary animals that had been injected with extra adrenaline fought off their tumors better than other sitting mice.

More remarkably, by studying the action of various genes within the cells of the mice, the scientists determined that adrenaline seemed to be sending biochemical signals to some of the animals’ IL-6 cells, making them physiologically more alert, so that when a tumor began to develop in the affected animal, those IL-6 cells in turn activated the natural killer cells in the bloodstream and actually directed them to the tumors, like minute guide fish.

Because the runners’ blood generally contained more adrenaline, more IL-6, and more natural killer cells than did the blood of the sedentary mice, this process was intensified. A larger number of natural killer cells were directed to tumors in the runners, allowing their immune systems, it seems, to more effectively combat the malignancy.

With these results, “we show that voluntary wheel running in mice can reduce the growth of tumors, and we have identified an exercise-dependent mobilization of natural killer cells as the underlying cause of this protection,” said Pernille Hojman, a researcher at the University of Copenhagen who oversaw the new study.

But mice, obviously, are not people, and it is impossible to know from this study whether a similar process occurs in humans, although exercise, particularly moderately intense exercise such as jogging, has been shown to increase adrenaline and the production of natural killer immune cells in people, Dr. Hojman said.

“So the mechanisms,” she said, that seemed to partially protect the running mice in this study from malignancies, “can also happen in people,” perhaps providing one more incentive, if we still need it, to get up and move.

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Which Type of Exercise Is Best for the Brain?

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Some forms of exercise may be much more effective than others at bulking up the brain, according to a remarkable new study in rats. For the first time, scientists compared head-to-head the neurological impacts of different types of exercise: running, weight training and high-intensity interval training. The surprising results suggest that going hard may not be the best option for long-term brain health.

As I have often written, exercise changes the structure and function of the brain. Studies in animals and people have shown that physical activity generally increases brain volume and can reduce the number and size of age-related holes in the brain’s white and gray matter.

Exercise also, and perhaps most resonantly, augments adult neurogenesis, which is the creation of new brain cells in an already mature brain. In studies with animals, exercise, in the form of running wheels or treadmills, has been found to double or even triple the number of new neurons that appear afterward in the animals’ hippocampus, a key area of the brain for learning and memory, compared to the brains of animals that remain sedentary. Scientists believe that exercise has similar impacts on the human hippocampus.

These past studies of exercise and neurogenesis understandably have focused on distance running. Lab rodents know how to run. But whether other forms of exercise likewise prompt increases in neurogenesis has been unknown and is an issue of increasing interest, given the growing popularity of workouts such as weight training and high-intensity intervals.

So for the new study, which was published this month in the Journal of Physiology, researchers at the University of Jyvaskyla in Finland and other institutions gathered a large group of adult male rats. The researchers injected the rats with a substance that marks new brain cells and then set groups of them to an array of different workouts, with one group remaining sedentary to serve as controls.

Some of the animals were given running wheels in their cages, allowing them to run at will. Most jogged moderately every day for several miles, although individual mileage varied.

Others began resistance training, which for rats involves climbing a wall with tiny weights attached to their tails.

Still others took up the rodent equivalent of high-intensity interval training. For this regimen, the animals were placed on little treadmills and required to sprint at a very rapid and strenuous pace for three minutes, followed by two minutes of slow skittering, with the entire sequence repeated twice more, for a total of 15 minutes of running.

These routines continued for seven weeks, after which the researchers microscopically examined brain tissue from the hippocampus of each animal.

They found very different levels of neurogenesis, depending on how each animal had exercised.

Those rats that had jogged on wheels showed robust levels of neurogenesis. Their hippocampal tissue teemed with new neurons, far more than in the brains of the sedentary animals. The greater the distance that a runner had covered during the experiment, the more new cells its brain now contained.

There were far fewer new neurons in the brains of the animals that had completed high-intensity interval training. They showed somewhat higher amounts than in the sedentary animals but far less than in the distance runners.

And the weight-training rats, although they were much stronger at the end of the experiment than they had been at the start, showed no discernible augmentation of neurogenesis. Their hippocampal tissue looked just like that of the animals that had not exercised at all.

Obviously, rats are not people. But the implications of these findings are provocative. They suggest, said Miriam Nokia, a research fellow at the University of Jyvaskyla who led the study, that “sustained aerobic exercise might be most beneficial for brain health also in humans.”

Just why distance running was so much more potent at promoting neurogenesis than the other workouts is not clear, although Dr. Nokia and her colleagues speculate that distance running stimulates the release of a particular substance in the brain known as brain-derived neurotrophic factor that is known to regulate neurogenesis. The more miles an animal runs, the more B.D.N.F. it produces.

Weight training, on the other hand, while extremely beneficial for muscular health, has previously been shown to have little effect on the body’s levels of B.D.N.F., Dr. Nokia said, which could explain why it did not contribute to increased neurogenesis in this study.

As for high-intensity interval training, its potential brain benefits may be undercut by its very intensity, Dr. Nokia said. It is, by intent, much more physiologically draining and stressful than moderate running, and “stress tends to decrease adult hippocampal neurogenesis,” she said.

These results do not mean, however, that only running and similar moderate endurance workouts strengthen the brain, Dr. Nokia said. Those activities do seem to prompt the most neurogenesis in the hippocampus. But weight training and high-intensity intervals probably lead to different types of changes elsewhere in the brain. They might, for instance, encourage the creation of additional blood vessels or new connections between brain cells or between different parts of the brain.

So if you currently weight train or exclusively work out with intense intervals, continue. But perhaps also thread in an occasional run or bike ride for the sake of your hippocampal health.

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Why We Get Running Injuries (and How to Prevent Them)

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Warm weather is on its way across the country — really, it is, I promise— and so are spring marathons, meaning that many people soon will begin a new or augmented running program. Many also will wind up sidelined by injury. But a new study suggests that being light on your feet could keep most runners healthy.

Running injuries are extremely common, with some statistics estimating that as many as 90 percent of runners miss training time every year due to injury.

But the underlying cause of many of these injuries remains in question. Past studies and popular opinion have blamed increased mileage, excess body weight, over-striding, modern running shoes, going barefoot, weak hips, diet, and rough pavement or trails. But most often, studies have found that the best indicator of a future injury is a past one, which, frankly, is not a helpful conclusion for runners hoping not to get hurt.

So for the new study, which was published in December in the British Journal of Sports Medicine, researchers at Harvard Medical School and other universities decided to look at running injuries, one of the more obvious but surprisingly understudied aspects of running, and to focus their attention, in part, on those rare long-time runners who have never been hurt.

Specifically, they set out to look at pounding, or impact loading, which means the amount of force that we create when we strike the ground. Pounding is, of course, inevitable during a run. But runners with similar body types and running styles can experience wildly different amounts of impact loading, and it hasn’t been clear to what extent these differences directly contribute to injuries.

The researchers recruited 249 experienced female recreational runners, who were chosen in part because they all struck the ground with their heels when they ran. Most runners are heel strikers, and heel striking is believed by many running experts to cause higher impacts than landing near the middle or front of the foot, possibly contributing to an increased risk of injuries. (The scientists focused on a single sex so that they would not have to control for gender in the results.)

The volunteers reported to the biomechanics lab at the Spaulding National Running Center, which is affiliated with Harvard Medical School, where they completed questionnaires about their injury history and then strode along a track equipped with force monitors to determine their impact loads.

Afterward, the scientists asked each volunteer to complete an ongoing, online running diary and injury log.

The researchers tracked the runners for two years.

During that time, more than 100 of the runners reported sustaining an injury that was serious enough to require medical attention. Another 40 or so reported minor injuries, while the rest remained uninjured.

More remarkably, in the minds of the researchers, 21 of the runners not only did not become injured during the two-year study but also had not had a prior injury. They remained long-term running-injury virgins, the athletic equivalent of unicorns.

Intrigued, the scientists decided to compare that small group’s impact loading with the pounding experienced by the seriously injured runners, since, the researchers theorized, the contrast between these groups should provide the most telling data about whether how hard you land affects your risk of being hurt.

The answer was that it does. The never-injured runners, as a group, landed far more lightly than those who had been seriously hurt, the scientists found, even when the researchers controlled for running mileage, body weight and other variables.

That finding refutes the widely held belief that a runner cannot land lightly on her heels.

“One of the runners we studied, a woman who has run multiple marathons and never been hurt, had some of the lowest rates of loading that we’ve ever seen,” said Irene Davis, a Harvard professor and director of the Spaulding center, who led the study. She pounded far less than many runners who land near the front of their feet, Dr. Davis said. “When you watched her run, it was like seeing an insect running across water. It was beautiful.”

The data also, however, contain a more general message for those of us who are not as wispy and whippy in our landings. Consciously think about “a soft landing,” Dr. Davis said. Some runners, especially those with a long history of injuries, might want to experiment with landing closer to the midfoot, she said, since many — but not all — runners naturally land more lightly when they don’t lead with the heel.

Consider, too, slightly increasing your cadence, she said, which is the number of steps you take per minute, a change that also tends to reduce the pounding from each stride. Or you might, as I plan to do, imagine that you are running over eggshells or, even more evocatively, are a water strider, moving gracefully and weightlessly across the pond.

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