Tagged Muscles

Do Statins Really Cause Muscle Aches?

People taking cholesterol-lowering statin drugs often report muscle pain, but the pain may be the same when they take a look-alike placebo pill.

Many people who take the cholesterol-lowering statin drugs report that they cause muscle pain, but a randomized trial suggests that the pain is no different when they take a placebo pill.

In rare cases, statins are known to cause a severe muscle condition called rhabdomyolysis, in which skeletal muscle tissue is destroyed, leading to serious complications. But much more frequently, people complain that the drugs simply cause muscle pain.

Whether statins are responsible for the muscle pain, however, remains uncertain. Muscle pain has many causes and is common in the older age group using statins, so determining whether statins are causing the pain is not easy. Results from observational studies, along with many media reports, may have led some to unnecessarily discontinue a treatment that is potentially lifesaving.

This new study, published in BMJ, involved a series of what is known as n-of-1 clinical trials, a methodology that allows researchers to examine the results of treatment and placebo in individual patients, rather than studying them as a group. In effect, each patient serves as his or her own control.

Mike Mergen for The New York Times

Researchers assembled 200 people in England and Wales who had either stopped or planned to stop taking statins because of intolerable muscle pain. For a year, each patient randomly took either a statin or a placebo pill over six two-month periods. Half the time they received 20 milligrams of Lipitor, and the other half they got a look-alike dummy pill. Until the end of the study, neither the researchers nor the patients knew when they were taking the statin and when they were taking the placebo.

During the last seven days of each two-month phase, the researchers measured each patient’s pain daily using a validated 10-point visual pain scale, with 10 indicating the worst possible pain. They also tracked other aspects of daily life, including the patient’s general activity level, mood, comfort in walking, ability to pursue normal work activities, social relationships, sleep and enjoyment of life.

The study found no differences between the statin and placebo periods in either muscle pain or reports on daily life activities and moods. Nine percent withdrew because of pain while they were on statins, but so did 7 percent who were taking placebos, an insignificant difference.

“These studies are difficult to do,” said Dr. Henry N. Ginsberg, a professor of medicine at Columbia who was not involved in the work. “This one is done as well as you can, and it’s a nice one to talk about with patients. You can tell your patients, ‘They’ve done studies in people like you, and these people couldn’t tell the difference between placebo and medicine.’”

Three months after the final treatment, when the patients had been informed of their results, the researchers asked them whether they had restarted statins, or intended to, and whether they found their own trial result helpful in making their decision. Most of the patients said that the trial was helpful, and more than two-thirds reported that they planned to start taking statins again.

The lead author, Dr. Liam Smeeth, a primary care physician and professor of clinical epidemiology at the London School of Hygiene and Tropical Medicine, said that when people stop statins because of muscle pain “they’re missing out on the huge benefits — reducing the risk of heart attack or stroke by about a third. What we’ve shown is that among these people who gave up their medicine because of pain — and their pain was real — it wasn’t made worse by statins.”

Why Exercise Can Be So Draining for People With Rheumatoid Arthritis

Even a gentle session of leg lifts set off an exaggerated nervous system reaction in older women with rheumatoid arthritis.

Exercise can feel more difficult and draining than usual if you have rheumatoid arthritis, and it’s not just because of the stiff and painful joints caused by this autoimmune disorder. In a groundbreaking new experiment involving older women and exercise, researchers found that even a gentle session of leg lifts set off an exaggerated nervous system reaction in those with rheumatoid arthritis. Light exercise also negatively affected the inner workings of their muscles and blood vessels.

The findings build on earlier research about rheumatoid arthritis and the nervous system and raise pressing new questions about the best and safest ways for people with this disorder or similar autoimmune diseases to become and remain active.

Anyone who has rheumatoid arthritis or is close to someone who has it knows the havoc it creates in the body. Immune cells mistakenly attack healthy tissue, especially in joints, causing swelling, pain and deterioration, along with full-body inflammation and fatigue. Rheumatoid arthritis also often results in cardiovascular disease, which initially puzzled doctors, since the misguided immune cells do not directly target the heart or arteries.

But in recent years, researchers discovered that people with rheumatoid arthritis tend to have unusually twitchy sympathetic nervous systems. The sympathetic nervous system is the portion of our internal wiring that stimulates the fight-or-flight response, biochemically alerting our brains, heart, muscles and other bodily systems to brace ourselves for impending danger. The opposing parasympathetic nervous system, the Matthew McConaughey of our internal biology, lulls us, sending signals that quiet the sympathetic upsets.

But in rheumatoid arthritis patients, researchers found, the sympathetic system seems stuck in overdrive, keeping people’s internal operations constantly on edge. A result is a high risk for elevated blood pressure and heart rate, even when people are resting quietly, which contributes over time to cardiovascular disease.

Few of those earlier studies, though, looked at exercise, which also raises blood pressure and heart rates and changes nervous system reactions. Some past studies — and considerable anecdotal evidence — had indicated that people with rheumatoid arthritis feel more fatigue during and after activity than other exercisers. Their heart rates and blood pressures also remain stubbornly elevated for longer after workouts. But what might be going on inside their nerves and muscles leading to these reactions has been mostly unclear.

So, for the new study, which was published in February in The Journal of Physiology, scientists at the University of São Paulo in Brazil decided to ask people with rheumatoid arthritis to do a little resistance training. Turning to patients at the university’s rheumatology clinic, they recruited 33 older women with rheumatoid arthritis and another 10 older women without the condition, to serve as controls. Most of them, in both groups, were on various medications.

They invited all of their volunteers to the lab, drew blood, asked about their current pain levels, tested blood pressure and other health markers, and gently embedded tiny sensors beneath the skin in one leg to measure nervous system activity. Finally, they asked each woman to complete leg lifts with that leg, using a standard weight machine set to a low resistance. The women were supposed to lift repeatedly for three minutes — although some quit earlier than that — while the researchers tracked their blood pressures, nervous system reactions, and markers of muscular response, during and immediately afterward.

What they found when they compared results was that “the women with R.A. showed greater blood pressure and sympathetic responses” to the light workout than those in the control group, says Tiago Peçanha, a postdoctoral research associate at the University of São Paulo who was a co-author of the new study with his doctoral adviser Hamilton Roschel, the director of the university’s Laboratory of Assessment and Conditioning in Rheumatology, and others.

Their nerves seemed especially sensitive to the buildup of certain substances in the working muscles, the researchers concluded, which prompted the nerves to send urgent messages to nearby blood vessels, ordering them to contract. The result was lingering high blood pressure, during and after the workout.

These reactions were most marked among the rheumatoid arthritis patients with the highest levels of inflammatory activity in their blood before the exercise, the researchers found.

Taken as a whole, the findings indicate that physical activity can be extra difficult for people with rheumatoid arthritis, because their nervous systems may overreact to relatively minor changes inside the muscles.

But the findings do not suggest that those with the autoimmune disorder should avoid exercise, Dr. Roschel says. “Physical activity is highly recommended for people with R.A,” he points out. “But these individuals may require additional attention and support to engage in physical activity programs.”

If you have been diagnosed with rheumatoid arthritis, talk with your physician or an exercise physiologist about how best to exercise, he says. And if you begin a new routine, start slowly and perhaps keep a log of how you feel during workouts.

Of course, this study focused on older women with rheumatoid arthritis and a single session of very light resistance training. It is unknown whether the results apply equally to younger women or men with the condition, or whether other types of exercise, such as walking, may produce a similar response. It is also unknown how those with different autoimmune diseases or related conditions might be affected.

Dr. Roschel and his colleagues are looking into all of those questions, though. “We have also been conducting some exercise studies with patients who have recovered from Covid-19 in our lab, and they also present abnormal cardiorespiratory responses to exercise,” he says. They hope to publish additional studies soon.

Ice for Sore Muscles? Think Again.

After a particularly vigorous workout or sports injury, many of us rely on ice packs to reduce soreness and swelling in our twanging muscles. But a cautionary new animal study finds that icing alters the molecular environment inside injured muscles in detrimental ways, slowing healing. The study involved mice, not people, but adds to mounting evidence that icing muscles after strenuous exercise is not just ineffective; it could be counterproductive.

Check inside the freezers or coolers at most gyms, locker rooms or athletes’ kitchens and you will find ice packs. Nearly as common as water bottles, they are routinely strapped onto aching limbs after grueling exercise or possible injuries. The rationale for the chilling is obvious. Ice numbs the affected area, dulling pain, and keeps swelling and inflammation at bay, which many athletes believe helps their aching muscles heal more rapidly.

But, in recent years, exercise scientists have started throwing cold water on the supposed benefits of icing. In a 2011 study, for example, people who iced a torn calf muscle felt just as much leg pain later as those who left their sore leg alone, and they were unable to return to work or other activities any sooner. Similarly, a 2012 scientific review concluded that athletes who iced sore muscles after strenuous exercise — or, for the masochistically minded, immersed themselves in ice baths — regained muscular strength and power more slowly than their unchilled teammates. And a sobering 2015 study of weight training found that men who regularly applied ice packs after workouts developed less muscular strength, size and endurance than those who recovered without ice.

But little has been known about how icing really affects sore, damaged muscles at a microscopic level. What happens deep within those tissues when we ice them, and how do any molecular changes there affect and possibly impede the muscles’ recovery?

So, for the new study, which was published in March in the Journal of Applied Physiology, researchers at Kobe University in Japan and other institutions, who long had been interested in muscle physiology, gathered 40 young, healthy, male mice. Then, using electrical stimulation of the animals’ lower legs to contract their calf muscles repeatedly, they simulated, in effect, a prolonged, exhausting and ultimately muscle-ripping leg day at the gym.

Melody Melamed for The New York Times

Rodents’ muscles, like ours, are made up of fibers that stretch and contract with any movement. Overload those fibers during unfamiliar or exceptionally strenuous activities and you damage them. After healing, the affected muscles and their fibers should grow stronger and better able to withstand those same forces the next time you work out.

But it was the healing process itself that interested the researchers now, and whether icing would change it. So, they gathered muscle samples from some animals immediately after their simulated exertions and then strapped tiny ice packs onto the legs of about half of the mice, while leaving the rest unchilled. The scientists continued to collect muscle samples from members of both groups of mice every few hours and then days after their pseudo-workout, for the next two weeks.

Then they microscopically scrutinized all of the tissues, with a particular focus on what might be going on with inflammatory cells. As most of us know, inflammation is the body’s first response to any infection or injury, with pro-inflammatory immune cells rushing to the afflicted area, where they fight off invading germs or mop up damaged bits of tissue and cellular debris. Anti-inflammatory cells then move in, quieting the inflammatory ruction, and encouraging healthy new tissue to form. But inflammation is often accompanied by pain and swelling, which many people understandably dislike and use ice to dampen.

Looking at the mouse leg muscles, the researchers saw clear evidence of damage to many of the muscles’ fibers. They also noted, in the tissue that had not been iced, a rapid muster of pro-inflammatory cells. Within hours, these cells began busily removing cellular debris, until, by the third day after the contractions, most of the damaged fibers had been cleared away. At that point, anti-inflammatory cells showed up, together with specialized muscle cells that rebuild tissue, and by the end of two weeks, these muscles appeared fully healed.

Melody Melamed for The New York Times
Melody Melamed for The New York Times

Not so in the iced muscle, where recovery seemed markedly delayed. It took seven days in these tissues to reach the same levels of pro-inflammatory cells as on day three in the unchilled muscle, with both the clearance of debris and arrival of anti-inflammatory cells similarly slowed. Even after two weeks, these muscles showed lingering molecular signs of tissue damage and incomplete healing.

The upshot of this data is that “in our experimental situation, icing retards healthy inflammatory responses,” says Takamitsu Arakawa, a professor of medicine at Kobe University Graduate School of Health Sciences, who oversaw the new study.

But, as Dr. Arakawa points out, their experimental model simulates serious muscle damage, such as a strain or tear, and not simple soreness or fatigue. The study also, obviously, involved mice, which are not people, even if our muscles share a similar makeup. In future studies, Dr. Arakawa and his colleagues plan to study gentler muscle damage in animals and people.

But for now, his study’s findings suggest, he says, that damaged, aching muscles know how to heal themselves and our best response is to chill out and leave the ice packs in the cooler.

Too Much High-Intensity Exercise May Be Bad for Your Health

A new study hints that excessive HIIT may harm your mitochondria, the energy generators found in every cell of your body.

If high-intensity exercise is good for us, is more necessarily better?

Maybe not, according to an admonitory new study of the molecular effects of high-intensity interval training, also known as HIIT. In the study, people who began working out strenuously almost every day developed sudden and severe declines in the function of their mitochondria, which are the energy powerhouses inside of cells, along with incipient signs of blood sugar dysfunction.

Their metabolic issues started to reverse when they dialed back on their workouts but did not disappear, suggesting that the benefits of extremely vigorous exercise may depend on just how much we do.

At this point, almost anyone with an interest in fitness is familiar with the concept and appeal of high-intensity interval training. Consisting of repeated, brief spurts of hard exercise interspersed with a few minutes of rest, HIIT workouts can be quite short but are still able to improve substantially our aerobic fitness and many other aspects of our health. Studies show, for example, that intense bursts of exercise increase the number of mitochondria in our muscle cells, and more mitochondria are thought to contribute to better cellular and metabolic health.

But recent research has begun to hint that HIIT also may have unexpected downsides. In a study I wrote about in January, people who worked out with HIIT routines three times a week for six weeks did not improve their blood pressure or body fat as much as people who exercised far more moderately five times a week.

The authors of that study speculated that, by being sedentary for four days each week, the intense exercisers in the study may have undermined the otherwise potent effects of their HIIT sessions. On a weekly basis, they were not exercising enough.

But whether it would be advisable to do more HIIT sessions in a single week has not been clear. Most past studies and formal recommendations about intense workouts top out at three sessions a week, and few researchers have looked into how HIIT-ing harder or more often might affect health.

So, for the new study, which was published recently in the journal Cell Metabolism, researchers at the Swedish School of Sport and Health Sciences and the Karolinska Institute, both in Stockholm, set out, like Goldilocks, to sample different amounts of weekly hard exercise and see if any might be just right.

They began by recruiting 11 healthy men and women who exercised but were not competitive athletes. These volunteers visited the researchers’ lab for tests of their current fitness and metabolic health, including blood-sugar levels over the course of a day.

Then the volunteers began an ambitious exercise program. During the first week, they performed two sessions of HIIT, repeating four-minute-long intervals five times on a stationary bicycle, with three minutes of rest in between. The riders pedaled as hard as they could during each four-minute surge, while researchers monitored their power output. Afterward, the researchers biopsied leg muscles and rechecked the riders’ fitness and 24-hour blood-sugar control.

During week two, the riders added a third HIIT session and ramped up the length of some of their intervals to a draining eight minutes. In week three, they worked out five times, with a mix of four-minute and eight-minute spurts of all-out pedaling. Finally, in week four, for recovery, they effectively halved the amount and intensity of their exercise. Each week, the researchers repeated all testing.

Then they compared how people’s bodies had changed week over week.

At first, the findings were encouraging. By the end of week two, the riders were pedaling harder and appeared to be getting fitter, with better daily blood-sugar control and more total mitochondria in their muscle cells. Each of these mitochondria was also more efficient now, producing greater amounts of energy than at the start.

But something began to go wrong during week three. The volunteers’ ability to generate power while cycling flattened, and their subsequent muscle biopsies showed sputtering mitochondria, each of which was now producing only about 60 percent as much energy as during the previous week. The riders’ blood-sugar control also slipped, with seesawing spikes and dips throughout the day.

After a week of lower-intensity riding, their mitochondria started to bounce back, producing more energy, but still 25 percent less than during week two. Their blood-sugar levels also stabilized, but again, not to the same extent as before. The riders could pedal, however, with the same — or even greater — vigor as in week two.

Taken as a whole, the monthlong experiment suggests that “HIIT exercise should not be excessive if increased health is a desired outcome,” says Mikael Flockhart, a doctoral student at the Swedish School of Sport and Health Sciences, who conducted the study with his adviser, Filip Larsen, and others.

The study was not focused on athletic performance, but even for serious athletes, he says, piling on multiple, intense, interval workouts each week, with little rest between them, is likely to lead to a tipping point, after which performance, as well as indicators of metabolic health, slip.

The researchers are not sure precisely what changes within their volunteers’ bodies and muscles precipitated the negative results in week three. They tested multiple potential molecular causes, Mr. Flockhart says, but did not isolate an obvious, single instigator. He and his colleagues suspect that a cascade of biochemical changes within people’s muscles during the hardest week of exercise overwhelmed the mitochondria then, and the weakened mitochondria contributed to the disruptions in people’s blood-sugar control.

This study was small, though, and quite short-term, with barely a week of each exercise routine. It also featured healthy volunteers, so does not show whether results would be the same, better or worse in people with existing metabolic problems.

Even so, the findings strongly suggest that anyone interested in high-intensity interval training start small, Mr. Flockhart says. Train a few times a week and on the remaining days, maybe take a walk.

The Hardship of Social Distancing When Touch Is a Lifeline

Sonali Gupta, who has limb-girdle muscular dystrophy, gets help from her caregiver, Martha Tirki, at her apartment in Mumbai.
Sonali Gupta, who has limb-girdle muscular dystrophy, gets help from her caregiver, Martha Tirki, at her apartment in Mumbai.Credit…Atul Loke for The New York Times

Voices

The Hardship of Social Distancing When Touch Is a Lifeline

For me, and many others with physical disabilities, touch is not merely a luxury or a pleasure, but an aspect of my functionality, my basic survival.

Sonali Gupta, who has limb-girdle muscular dystrophy, gets help from her caregiver, Martha Tirki, at her apartment in Mumbai.Credit…Atul Loke for The New York Times

  • Feb. 10, 2021, 11:36 a.m. ET

The sun broke through the cream-colored blinds at my mother’s New Jersey home. I felt its warmth on my face before throwing my body weight to one side, trying once again to roll and push up to sit.

I hoped the sudden movement would give me some momentum, but it wasn’t enough and I rolled back down, my back once again flat against the bed, sinking deeper into the plush mattress my mother had bought for me when I returned to her home.

In my bedroom in Mumbai, my mattress is made of high-density foam, a better surface to move on for someone like me, someone with muscular dystrophy. If I needed a hand to sit up, my live-in caregiver, Martha Tirki, was a holler away. But in New Jersey, my mother was still sleeping upstairs and I hated the thought of waking her up to help me. My part-time caregiver wouldn’t arrive for another hour. After more failed attempts with lots of twisting and turning, I finally sat up.

I took some seconds to feel good about this because it was easy to think otherwise, to think: All of that and I haven’t even gotten out of bed yet.

It was 12 years ago when I learned I had limb-girdle muscular dystrophy, or LGMD, a rare and progressive muscle-wasting disease. Before that I’d been a fully functional, independent young woman about to graduate from New York University. I had well-oiled friendships and an active social life. I had job offers and a head full of dreams. But I would suddenly fall while walking to class. And it became harder to climb the subway stairs.

My family and I got genetically tested and discovered that my parents carried a defective recessive gene, a gene that forever changed the way I’d interact with the world around me. A gene that eventually meant I wouldn’t be able to take care of myself alone anymore.

As my disease progressed, it ushered in a way of living that made other people’s hands a crucial part of my most basic activities. For me, and many others with physical disabilities, touch is not merely a luxury or a pleasure, but an aspect of my functionality, my basic survival. Many other people’s hands were now a part of my daily routines.

That is, until Covid descended on the world.

Ms. Tirki helps support the author.
Ms. Tirki helps support the author.Credit…Atul Loke for The New York Times

My parents are both doctors who are originally from North India. In 2008, I traveled to India with my father in search of an alternative cure for my condition. I ingested ayurvedic herbs in Pune, consulted healers and astrologers in Mangalore and learned yoga at ashrams in Rishikesh in an effort to arrest my body’s degeneration.

When that didn’t work, I returned to New York and attempted to resume the life I had left behind. I got a job and insisted I could live alone. But it wasn’t long before I needed help with everything from showering to walking to cooking to driving and sometimes even sitting up. I ended up returning to India for a stem cell procedure that seemed promising, and living in Mumbai for its accessible physical therapy and home care options, two essential services that have kept me functional and semi-independent. Now more than ever, other people’s hands were my lifelines.

And so I came to rely on people and their hands. People like Verna, my physical therapist, whose intuitive hands perfectly positioned my legs as we worked individual muscles during our sessions. Or Anjali, my aqua therapist, whose soft hands stabilized the forward tilt of my pelvis as we walked together underwater. Or Sheila, my masseuse, whose heavy hands rubbed out the soreness in my muscles and brought new life to underused or atrophied parts of my body. Or Karishma, my yoga teacher, whose hands stretched my arms overhead because they couldn’t do that on their own. Or Martha, who held my cup of tea in the morning with one hand and held me with the other as we walked over to my customized desk and chair so I could write. When I was ready to shower, she hoisted me up and we locked hands as we moved on to the next activity.

The author on her balcony in Mumbai.Credit…Atul Loke for The New York Times

During our leg exercise routine, Verna held her palm against my knee and told me that all I needed was a slight, supportive touch and my body would take care of the rest. Sometimes I wasn’t able to tell if she was moving my leg or whether my muscles were performing the exercise on their own. But it didn’t matter. Much of the time it was about knowing that her hands were there to support me if I needed them.

My body and mind rely on touch as a means of support, as a method of surviving and navigating a life with muscular dystrophy. When India’s lockdown hit, my therapy stopped abruptly. I continued sessions on Zoom while Martha tried to help me keep up with the exercises, but it wasn’t enough. I needed trained hands on my body, and I wasn’t sure what would happen without them.

Before the pandemic, I’d recruit help from a nearby stranger or security guard outside a building I was entering and they almost always assisted me. Now asking for a hand, even if it was gloved, was dangerous, sometimes even impossible. I was being met with suspicious stares and mumbles under half-hidden faces. I felt helpless and yet I understood. Touching someone you didn’t know, or even someone you did, could mean contracting a mysterious, invisible illness — or worse — death.

After relying on so many hands to help me, I was left with only two, those of Martha, who took great care of me the first several months of the pandemic. I was grateful for her help and felt the significance of our pairing the longer the lockdown persisted.

Still, I felt deprived of the comfort that came from touching my loved ones. In July, I flew back to New Jersey for hugs from my family and to curl into bed with my mother at night, warming her feet with mine. Martha returned to her village because she didn’t have a passport. I cried deeply when we parted ways.

Even though I tried to stay active in New Jersey, I worried about exposing my parents to too many caregivers, so I couldn’t receive the same care I did in India. With Covid cases raging across the country, I wondered when we would ever touch again.

With India’s ambitious plan to roll out the vaccines, I returned to Mumbai not long ago, back to Martha and my other caregivers, to the hands that once touched me. I need extra support for my body now, which is a vulnerable thing to ask for at any time, and especially during a pandemic. After I completed my quarantine, I got back to my normal activities, including physical therapy. It felt surreal to see my therapists, to get back in the pool and move my body again with the help of other people.

At home, I look out over the balcony to see people wearing masks and carrying on with their lives. Streets that were once empty are now full of noise. Schools have not reopened since the lockdown, and the numbers of cases and deaths in the country have dropped.

I’m working on getting registered for the vaccine soon not only for myself but because I need so many people to help me, I am constantly in the position of putting others at risk.

As more of the world gets vaccinated, our physical interactions will change again. And with that change comes a deeper understanding of what it means to ask for a hand.

Sonali Gupta is a writer based in Mumbai who is working on a book about her search for a cure for limb-girdle muscular dystrophy.

Running Is a Total Body Affair

Phys Ed

Running Is a Total Body Affair

We can thank our heads and shoulders — and not just our knees and toes — that we evolved to run as well as we do.

Credit…Edward Muybridge/Getty Images
Gretchen Reynolds

  • Feb. 10, 2021, 5:00 a.m. ET

We can thank early human evolution that many of us can enjoy running as much as we do. Watch anyone with a ponytail run, and you can see their hair repeatedly describe a figure-eight in the air, responding to the forces generated by the running. But their heads stay still, their eyes and gaze level.

If it weren’t for some unique evolutionary advances, our heads would do the same as that ponytail, flopping like a swim noodle when we run, according to a clever new study of how — and why — our upper bodies seem to work the way they do when we run, but not when we walk. The study, which involved treadmills, motion capture, hand weights and an eon’s worth of back story, finds that an unusual coordination between certain muscles in runners’ shoulders and arms helps to keep heads stable and runners upright.

The new findings may answer lingering questions about the role of our upper bodies in running and why we, unthinkingly, bend and swing our arms with each stride. They also add to the mounting evidence that, long ago, distance running began shaping human bodies and lives in ways that still reverberate today.

The possibility that we humans are born to run has inspired many studies, books, lectures and debates in recent years, including the journalist Christopher McDougall’s 2009 best seller, “Born to Run.” The idea is based on fossil research indicating that early humans evolved to have distinctive leg bones and other characteristics that would have aided distance running. The findings suggest that those of our ancestors who could run well dominated in the procuring-food and procreating sweepstakes, so that natural selection started favoring physical characteristics associated with running.

Much of this research came from the mind and laboratory of Daniel Lieberman, a professor of human evolutionary anatomy at Harvard University and author of the new book “Exercised,” which delves into exercise and evolution. At first, most of his and other scientists’ work related to evolution and running centered on lower bodies, since legs play such an obvious part in how we get from one place to another.

But Dr. Lieberman also was interested in runners’ upper bodies and, especially, their heads. As a longtime marathon runner himself, he knew that a stable head is critical for successful running, but not necessarily a simple thing to achieve. Running is propulsive. You push off, rise and then brake forcefully against the ground with every stride, placing forces on your head that could make it flop uncontrollably, like that bobbing ponytail.

How we manage to keep our heads stable, however, has not been altogether clear. Like most cursorial species, or animals that run, including dogs and horses, we have a well-developed nuchal ligament, a tissue that connects the skull and neck. That is not the case in species that aren’t natural runners, like apes or swine.

When he was a young scientist, Dr. Lieberman recalled, he enticed pigs — who are inelegant runners — onto treadmills to study their biomechanics. Their heads jiggled like bobbleheads when they were forced to run, prompting Dr. Lieberman and his colleagues to conclude they lacked a nuchal ligament, a finding borne out by anatomical studies.

But we humans also have the challenge of being upright, on two legs. Presumably to balance ourselves while running, we began, at some point, to swing our arms. Dr. Lieberman guessed that the arm swing helped to stabilize our heads. But, if so, there would have to be coordination between the muscles in our forearms and shoulders, he thought, even though these muscles do not physically connect. They would need to fire together and with comparable force during running, if they were to be successful in stabilizing our heads.

He was uncertain about how to test that theory, though, until his colleague Andrew Yegian, a college fellow in the department of human evolutionary biology at Harvard, suggested weighting runners’ arms and heads. Add mass there, he said, watch how the muscles respond, and you would be able to tell if the arms and shoulders were working together to steady the head or not.

So, for the new study, which was published last month in the American Journal of Physical Anthropology, Dr. Lieberman, Dr. Yegian and their colleagues fitted 13 men and women with sensors on their upper bodies that track muscle activity and asked them to, first, walk and then run on a treadmill while the researchers filmed them with motion-capture technology. Then the scientists handed the volunteers light hand weights and asked them to run again. Finally, they strapped weighted masks to the volunteers’ faces and had them run once more, before comparing how everyone’s muscles had responded to each of these interventions.

It turned out that not much of interest happened while the study volunteers walked; the muscles in their forearms and shoulders showed no evidence of coordinated activity. But those same muscles snapped into synchronized action when the volunteers started to run; the muscles began firing at the same time and with about the same amount of force.

That synchrony grew during the weighted runs. When the volunteers carried weights and their forearm muscles fired with extra force to compensate, the muscles in their shoulders did the same. Similarly, when their weighted faces prompted the runners’ shoulder muscles to fire more forcefully, their arm muscles did likewise.

The study does not explain how these widely separate muscles communicate with one another, though. Nor can the findings pinpoint when, in our existence as a species, they may have started to work together in this way. It also does not prove that all of us are natural born runners; plenty of people do not enjoy the sport.

Still, the results do tell us more than we knew before about our bodies, Dr. Lieberman says, and underscore that running molded us as a species. “If we didn’t have to run” in our early days as humans, he says, “we wouldn’t have this system” of muscular interplay today.

Can 4 Seconds of Exercise Make a Difference?

Phys Ed

Can 4 Seconds of Exercise Make a Difference?

Four seconds of intense intervals, repeated until they amount to a minute of total exertion, led to rapid improvements in strength and fitness in middle-aged and older adults.

Credit…iStock
Gretchen Reynolds

  • Dec. 30, 2020, 5:00 a.m. ET

In what is probably the definitive word on how little exercise we can get away with, a new study finds that a mere four seconds of intense intervals, repeated until they amount to about a minute of total exertion, lead to rapid and meaningful improvements in strength, fitness and general physical performance among middle-aged and older adults.

The study relied on a type of specialized stationary bicycle that is not widely available, but, even so, the results suggest that strenuous but super-abbreviated workouts can produce outsize benefits for our health and well-being, a timely message as we plan our New Year’s exercise resolutions.

I have often written about the potential benefits of brief, high-intensity interval training, or H.I.I.T., an approach to exercise that consists of quick spurts of draining physical effort, followed by rest, with the sequence repeated multiple times. In studies, short H.I.I.T. workouts typically produce health gains that are equal to or more pronounced than much longer, gentler workouts.

But the ideal length of the intervals in these workouts has been unsettled. Researchers studying H.I.I.T. agree that the optimal interval span should stress our muscles and other bodily systems enough to jump-start potent physiological changes but not so much that we groan, give up and decline to try that workout ever again. In practice, those dueling goals have led H.I.I.T. scientists to study intervals ranging from a protracted four minutes to a quickie 20 seconds.

But Ed Coyle, an exercise physiologist at the University of Texas in Austin, and his graduate assistant Jakob Allen suspected that even 20-second spurts, performed intensely, might exceed some exercisers’ tolerance. So, he decided to start looking for the shortest possible interval that was still effective.

And in the new study, which was published this week in Medicine & Science in Sports & Exercise, he and his colleagues settled on a blink-swift four seconds.

They arrived at that number by first working with competitive athletes at the university’s human performance lab. Muscular and fit, the athletes generated enormous speed and power on specialized stationary bicycles that feature a heavy flywheel and no resistance. During fitness testing on these bikes, most of the athletes would reach their maximum power output and all-out aerobic effort after about two seconds of hard pedaling. (Dr. Coyle has equity in the company that manufactures the bicycles, but says this monetary involvement does not affect research results from his lab.)

The rest of us, Dr. Coyle and his colleagues reasoned, probably would require twice as long — or about four seconds. By that point, the researchers thought, most people should have massively stimulated their muscles and aerobic systems but not yet exhausted them. If the riders then rested for a minute or so before sprinting again, they should be able to repeat the all-out efforts again and again.

To test that idea, the researchers turned initially to eight healthy college students, asking them to sprint on the bikes for four seconds periodically throughout the day, to see if these short, strenuous workouts would counteract some of the undesirable metabolic effects of sitting all day and eating poorly. They did, as I wrote about in April.

But that study focused on robust, young adults and repeated, if diminutive, workouts sprinkled throughout the day. The scientists now wondered if a more practical, single session of four-second sprints would be enough exercise to improve health and fitness in out-of-shape adults well past their college years.

So, they recruited 39 of them, men and women aged 50 to 68 who were sedentary but had no other major health concerns. They tested the volunteers’ current aerobic fitness, muscular power and mass, arterial flexibility, and ability to perform what are called “activities of daily living,” such as getting up out of a chair.

The volunteers began visiting the performance lab three times a week. There, they completed a brief workout of repeated four-second intervals on the lab’s specialized bikes. At first, they sprinted for four seconds, with Dr. Allen calling out a second-by-second countdown, followed by 56 seconds of rest, repeating that sequence 15 times, for a total of 60 seconds of intervals.

Over two months, though, the riders’ rest periods declined to 26 seconds and they increased their total number of sprints to 30 per session.

At the end of eight weeks, the scientists retested everyone and found substantial differences. On average, riders had increased their fitness by about 10 percent, gained considerable muscle mass and strength in their legs, reduced the stiffness of their arteries and outperformed their previous selves in activities of daily living, all from about three to six minutes a week of actual exercise.

A majority of the volunteers also told the researchers during follow-up interviews that they enjoyed the workouts and would continue them, if possible, Dr. Coyle said.

The upshot, he said, is that these intervals, despite being as brief as possible, effectively boosted health and fitness in ordinary adults.

Of course, most of us do not have access to the kind of specialized stationary bicycles used in this study. Nor do we have a researcher helpfully hollering out four-second countdowns for us. To reach similar, all-out efforts in more typical workouts, Dr. Coyle said, we might need to sprint up a hill or staircase as hard as possible or run and jump in place vigorously or furiously pedal our spin bike.

In these situations, the time needed to achieve all-out effort is likely to be more than four seconds, he said. But even if the time commitment is doubled, most of us probably could resolve to exercise in 2021 often and intensely for eight seconds at a time.

Attention, Teenagers: Nobody Really Looks Like That

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Credit Anna Parini

The universal truth of puberty and adolescence is body change, and relatively rapid body change. Teenagers have to cope with all kinds of comparisons, with their peers, with the childhood bodies they leave behind, and with the altered images used in advertising and in the self-advertising on social media.

It may be that the rapid way the body changes during these years can help adolescents believe in other kinds of change, including the false promises that various products can significantly modify their size and shape. A study published last month in the journal Pediatrics looked at two kinds of risky behavior that are increasingly common over adolescence: the use of laxatives for weight loss and the use of muscle-building products.

It used data from an ongoing study of more than 13,000 American children, the Growing Up Today Study (GUTS). The participants’ mothers took part in the Nurses’ Health Study II, and the children were recruited in 1996, when they were 9 to 14 years old, and surveyed about a variety of topics as they grew up.

By age 23 to 25, 10.5 percent of the women in this large sample reported using laxatives in the past year to lose weight; the practice increased over adolescence in the girls, but was virtually absent among the boys. Conversely, by young adulthood, about 12 percent of the men reported use of a muscle-building product in the past year, and again, this increased during adolescence.

So a lot of young women are taking laxatives to try to become very thin, and a lot of young men are using products to help them bulk up and become more muscular. The researchers were interested in how these practices were associated with traditional ideas of masculinity and femininity. They found that, regardless of sexual orientation, kids who described themselves as more gender conforming were more likely to use laxatives (the girls) or muscle-building products (the boys).

“The link is the perception that they are going to alter your weight, shape, appearance,” said Rachel Rodgers, a counseling psychology researcher who studies body image and eating concerns and is an associate professor of applied psychology at Northeastern University.

“The representations of ideal appearance in society are very restrictive and very unrealistic both for men and for women,” she said. “They portray bodies that are unattainable by healthy means.”

Jerel Calzo, a developmental psychologist who is an assistant professor at Harvard Medical School, and the lead author on the study, said that one important aspect of this research was the way it highlighted the vulnerability of those who identify with traditional gender ideals.

“Usually in research we tend to focus on youth who are nonconforming, who we might focus on as more at risk for negative health outcomes, depression, who might be ostracized or victimized,” he said. But there are risks as well for those who are trying to measure up to what they see as the conventional standard.

The GUTS participants were asked to describe themselves as children in terms of the games they liked and the movie and TV characters they imitated, and this was used to score them as more or less “gender conforming.”

The early patterns of gender conformity were significant, Dr. Calzo said, because they were linked to behaviors that lasted through adolescence and into young adulthood. “Laxative use increases with age, muscle-building product use increases with age,” he said. “There is a need for early intervention.”

Chronic use of laxatives can affect the motility of the bowel so that it can be hard to do without them, and overdoses can alter the body’s balance of electrolytes, to a really dangerous extent.

“There’s a lot of shame and guilt for laxative abuse,” said Sara Forman, an adolescent medicine specialist who is the director of the outpatient eating disorders program at Boston Children’s Hospital. And many products marketed as cleanses or herbal teas are not labeled as laxatives, though they contain strong laxative ingredients.

The muscle-building products in the study included steroids, creatine and several others. The risks of steroids are well known, from hormonal imbalances and shrinking testicles to acne and aggression. With other commercial muscle-building products, the risks may have more to do with the lack of regulation, Dr. Calzo said. The products can contain banned substances or analogues of banned substances, like the amphetamine analogue found in popular diet and workout supplements last year.

And of course, the muscle-building products won’t reshape you into the photoshopped model any more than the laxatives will.

As Dr. Calzo says, we need to worry about the vulnerabilities of children who are growing up with issues of gender identity and sexuality. But don’t assume that more “mainstream” or “conforming” kids have it easy when it comes to body image. Parents can help by keeping the lines of communication open and starting these conversations when children are young. We should be talking about the images that our children see, about how real people look and how images are altered.

And that conversation should extend to social media as well; in a review by Dr. Rodgers, increased social media use was correlated with body image worries. “Teenagers are looking at their friends on social media and seeing photos that have been modified and viewing them as something real.”

The other message for parents is about helping to model healthy eating, family meals, realistic moderation around eating and exercising, and to refrain from any kind of negative comments or teasing about a child’s body. “Research has shown people who have more body satisfaction actually take care of themselves better, which suggests that the approach of making them feel bad is actually not helpful,” Dr. Rodgers said.

Every adolescent, across gender, gender identity, gender conformity, and sexuality, lives with a changing body and the need to navigate body image and identity. There are a lot of unrealistic images out there to measure yourself against, and a lot of false promises about how you might get there.

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Can Running Make You Smarter?

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Credit Getty Images

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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Learning to Walk in My 60s

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The author, Jacques Leslie, taking a step.

The author, Jacques Leslie, taking a step.Credit Blink Inc.

I knew about my limp before I knew much else about myself. It was 1951, at the height of the polio epidemic, and I was a 4-year-old in Beverly Hills, Calif. My father took me swimming in the pool of a club where he played tennis. Sometime later, a woman who’d swum in the pool a week or two before me was stricken with polio. A few days after that, while we were on vacation, I began limping and developed a fever.

After a doctor paid a visit to our hotel room and somberly conferred with my parents, they drove me to the Los Angeles County Hospital, where I spent a night or two in a hallway with dozens of other patients because the polio wards were full. For reasons I never grasped, I was sometimes tied to the bed, even though I clearly wasn’t going anywhere. I’d noticed that my right leg was numb, and I could no longer move it.

By the time I got home from the hospital a month later, I could walk, but only a few steps at a time. I remember once collapsing at the top of our staircase and waiting for someone to carry me back to my room. The disease shortened my right leg, partially atrophied my calf muscle, limited my ankle’s flexibility and curled my foot perceptibly inward.

Over the next decade I saw doctors regularly, performed daily exercises supervised by my stern father, and for months at a time wore corrective plaster-of-paris casts intended to twist my foot back toward normalcy. None of this kept me from an active childhood. I loved baseball — I played catcher, of course — and loathed the coach who yelled at me for running slowly, as if I could will speed. I dreaded running laps in phys ed class, where I’d inevitably come in last. Because my balance was poor, I fell down often. And I hated dancing, which seemed to require everything I lacked.

But in some ways polio felt like a distinction. It handed me a knowledge that others didn’t have. It made me serious when most kids around me were anything but. I understood Chester, Marshal Dillon’s sidekick on “Gunsmoke,” who limped his way though television’s longest-running series. I grasped his isolation, his lack of confidence, his compensating insight into everyone else. If I wasn’t already destined to be an observer, polio made certain that I was one, and laid the foundation for my career as a professional observer, a journalist.

By the time I reached adulthood, I more or less forgot about my limp. I spent six years as a foreign correspondent, including two covering the Vietnam War (while I was classified 4-F because of my leg). I zealously exercised and paid no attention to the dipping of my right shoulder each time I put weight on my right leg. If someone asked me about the limp, I’d mention polio and told them I must be tired.

My polio story would have ended there if I hadn’t consulted a physical therapist named Lisa for an unrelated problem a couple of years ago.  “We have to change the way you walk,” was one of the first things she said to me, with an urgency that took me by surprise. I was 67, and the idea of changing my walk struck me as at least a few decades too late, if it had ever been possible at all. “No,” Lisa said. “If you don’t learn to walk properly, the older you get, the more likely you’ll fall down.”

After a close examination of my leg, she stunned me once more: “Your limp is probably unnecessary.” In becoming accustomed to limping as a child, she concluded, I’d sacrificed the tone of healthy muscles, from my abdominals to my toes, that supported walking. If I reawakened them, I’d have enough muscle to achieve a normal stride.

Over the next year and a half, I saw Lisa nearly 50 times. At the beginning of each session, she’d watch me walk, then devise a treatment plan on the spot. She didn’t go for broke, as a previous therapist had: Her approach was gradual and intuitive. The exercises she assigned me were challenging but not overwhelming, and seemed to build upon themselves.

Each day at home I worked with straps, bands, assorted balls and a low tottering platform on which I learned to keep my balance while standing on my right foot — something I’d always considered impossible. As the muscles kicked in, one by one, I realized how I’d maneuvered around their weakness. As I walked, I often held my left my arm slightly behind me, stiffly, as if on call to provide balance. When I sat down, I planted my left foot on the floor and curled my right foot behind it — only my left side was rooted in the ground.

My foot eventually flattened out. The shoulder dip disappeared. Walking stopped feeling like a chore. My daughter said she no longer heard the familiar ker-CHUNK ker-CHUNK of my old gait. My spirits improved. My confidence grew. My writing career even enjoyed an uptick. And why not? For the first time in my life, at nearly 70 years old, I was standing on my own two feet.

A former Los Angeles Times foreign correspondent, Jacques Leslie is the author of “The Mark: A War Correspondent’s Memoir of Vietnam and Cambodia.”

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Exercise Makes Our Muscles Work Better With Age

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Credit Getty Images

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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A Diet and Exercise Plan to Lose Weight and Gain Muscle

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If there is a holy grail of weight loss, it would be a program that allows someone to shed fat rapidly while hanging on to or even augmenting muscle. Ideally, it would also be easy.

A new study describes a workout and diet regimen that accomplishes two of those goals remarkably well. But it may not be so easy.

For most of us, losing weight and keeping it off is difficult. If you consume fewer calories than your body requires for daily operations, it turns to internal sources of fuel. Those sources consist of body fat and lean tissue, meaning muscle. When someone on a diet drops a pound of body mass (a measure that does not include water), much of that pound consists of fat. But about a third or more can be made up of muscle.

The problem with losing muscle is that, unlike fat tissue, muscle burns calories. Having less muscle means a lower resting metabolic rate, so you burn fewer calories throughout the day. Losing muscle may also discourage physical activity, which is important for maintaining weight loss.

So researchers have long been looking for weight loss programs that produce hefty amounts of fat loss but diminish any decline in muscle.

For scientists at McMaster University in Ontario, Canada, that goal seemed to demand a high dose of protein and also plenty of exercise.

As the scientists knew, amino acids in protein help muscle tissue to maintain itself and to grow. Many past studies have suggested that low-calorie but high-protein diets can result in less muscle loss than the same number of calories but less protein.

However, the best dosage of protein in these circumstances has remained unclear, as has the role, if any, for exercise.

So for the new study, which was published in The American Journal of Clinical Nutrition, the McMaster researchers rounded up 40 overweight young men who were willing to commit to an intensive weight-loss program and divided them in half.

All of the young men began a diet in which their daily calories were cut by about 40 percent (compared to what they needed to maintain weight). But for half of them, this consisted of about 15 percent protein, 35 percent fat and 50 percent carbohydrates.

The other 20 volunteers began a diet that mimicked that of the first group, except that theirs swapped the protein and fat ratios, so that 35 percent of their calories came from protein and 15 percent from fat. Over all, their protein intake was about three times the recommended dietary allowance for most people.

The researchers handled that switch by changing the make-up of a supplied drink. In the low-protein group, the beverage contained high-fat milk and no added protein. For the others, it consisted of low-fat milk and a large dollop of whey protein.

All of the men also began a grueling workout routine. Six days a week they reported to the exercise lab and completed a strenuous full-body weight training circuit, high-intensity intervals, or a series of explosive jumps and other exercises known as plyometric training.

The diet and exercise routine continued for four weeks, by the end of which time, “those guys were done,” said Stuart Phillips, who holds a research chair in skeletal muscle health at McMaster University and oversaw the study. “All they could talk about was food.”

The routine had succeeded in incinerating pounds from all of the participants. The men in both groups weighed about 11 or 12 pounds less, on average.

But it was the composition of that weight loss that differed. Unlike most people on low-calorie diets, the men on the high-protein regimen had actually gained muscle during the month, as much as three pounds of it. So in these men, almost all of the 11 or 12 pounds they had lost over all had been fat.

These results strongly suggest that extra protein is advisable during weight loss, Dr. Phillips said, to avoid stripping yourself of muscle.

But exercise is also key, Dr. Phillips continued, particularly weight training, since it is known to build muscle. Even the men on the lower-protein diet lost little muscle mass, he pointed out, which was unexpected and almost certainly due, he and his colleagues concluded, to exercise.

Of course, by the end of the month, none of the men wished to continue. This type of extreme calorie cutting combined with intense exercise “is not a sustainable program in the long term,” Dr. Phillips said. “It’s more a kind of boot camp,” he said, manageable in the short term by people who are very committed and generally very healthy.

He and his colleagues plan to conduct follow-up experiments to find a more realistic and sustainable program. They plan, too, to study female volunteers and play around with the diets’ composition, to establish definitively that it is extra protein and not reduced fat that promotes muscle gains.

In the meantime, for those hoping to become thin but not puny, various apps allow you to determine the percentage of your diet that is composed of protein. If it is below 10 or 15 percent, you might want to shift calories from fat to protein. Renew your gym membership, too.

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