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 TimesRodents’ 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 TimesMelody Melamed for The New York TimesNot 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.

People who tended to be sedentary were far more likely to be hospitalized, and to die, from Covid than those who exercised regularly.More exercise means less risk of developing severe Covid, according to a compelling new study of physical activity and coronavirus hospitalizations. The study, which involved almost 50,000 Californians who developed Covid, found that those who had been the most active before falling ill were the least likely to be hospitalized or die as a result of their illness.The data were gathered before Covid vaccines became available and do not suggest that exercise can substitute in any way for immunization. But they do intimate that regular exercise — whether it’s going for a swim, walk, run or bike ride — can substantially lower our chances of becoming seriously ill if we do become infected.Scientists have known for some time that aerobically fit people are less likely to catch colds and other viral infections and recover more quickly than people who are out of shape, in part because exercise can amplify immune responses. Better fitness also heightens antibody responses to vaccines against influenza and other illnesses.But infections with the novel coronavirus are so new that little has been known about whether, and how, physical activity and fitness might affect risks for becoming ill with Covid. A few recent studies, however, have seemed encouraging. In one, which was published in February in The International Journal of Obesity, people who could walk quickly, an accepted gauge of aerobic fitness, developed severe Covid at much lower rates than sluggish walkers, even if the quick striders had obesity, a known risk factor for severe disease. In another study of older adults in Europe, greater grip strength, an indicator of general muscle health, signaled lowered risks for Covid hospitalizations.But those studies looked at indirect measures of people’s aerobic or muscular fitness and not their actual, everyday exercise habits, so they cannot tell us if getting up and moving — or staying still — changes the calculus of Covid risks.So, for the new study, which was published Tuesday in the British Journal of Sports Medicine, researchers and physicians at Kaiser Permanente Southern California, the University of California, San Diego, and other institutions decided to compare information about how often people exercised with whether they wound up hospitalized this past year because of Covid.The Kaiser Permanente health care system was well suited for this investigation, because, since 2009, it has included exercise as a “vital sign” during patient visits. In practice, this means doctors and nurses ask patients how many days each week they exercise, such as by walking briskly, and for how many minutes each time, then add that data to the patient’s medical record.Now, the researchers drew anonymized records for 48,440 adult men and women who used the Kaiser health care system, had their exercise habits checked at least three times in recent years and, in 2020, had been diagnosed with Covid-19. The researchers grouped the men and women by workout routines, with the least active group exercising for 10 minutes or less most weeks; the most active for at least 150 minutes a week; and the somewhat-active group occupying the territory in between.The researchers gathered data, too, about each person’s known risk factors for severe Covid, including their age, smoking habits, weight, and any history of cancer, diabetes, organ transplants, kidney problems and other serious, underlying conditions.Then the researchers crosschecked numbers, with arresting results. People in the least-active group, who almost never exercised, wound up hospitalized because of Covid at twice the rate of people in the most-active group, and were subsequently about two-and-a-half times more likely to die. Even compared to people in the somewhat-active group, they were hospitalized about 20 percent more often and were about 30 percent more likely to die..css-1xzcza9{list-style-type:disc;padding-inline-start:1em;}.css-rqynmc{font-family:nyt-franklin,helvetica,arial,sans-serif;font-size:0.9375rem;line-height:1.25rem;color:#333;margin-bottom:0.78125rem;}@media (min-width:740px){.css-rqynmc{font-size:1.0625rem;line-height:1.5rem;margin-bottom:0.9375rem;}}.css-rqynmc strong{font-weight:600;}.css-rqynmc em{font-style:italic;}.css-yoay6m{margin:0 auto 5px;font-family:nyt-franklin,helvetica,arial,sans-serif;font-weight:700;font-size:1.125rem;line-height:1.3125rem;color:#121212;}@media (min-width:740px){.css-yoay6m{font-size:1.25rem;line-height:1.4375rem;}}.css-1dg6kl4{margin-top:5px;margin-bottom:15px;}.css-16ed7iq{width:100%;display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-align-items:center;-webkit-box-align:center;-ms-flex-align:center;align-items:center;-webkit-box-pack:center;-webkit-justify-content:center;-ms-flex-pack:center;justify-content:center;padding:10px 0;background-color:white;}.css-pmm6ed{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-align-items:center;-webkit-box-align:center;-ms-flex-align:center;align-items:center;}.css-pmm6ed > :not(:first-child){margin-left:5px;}.css-5gimkt{font-family:nyt-franklin,helvetica,arial,sans-serif;font-size:0.8125rem;font-weight:700;-webkit-letter-spacing:0.03em;-moz-letter-spacing:0.03em;-ms-letter-spacing:0.03em;letter-spacing:0.03em;text-transform:uppercase;color:#333;}.css-5gimkt:after{content:’Collapse’;}.css-rdoyk0{-webkit-transition:all 0.5s ease;transition:all 0.5s ease;-webkit-transform:rotate(180deg);-ms-transform:rotate(180deg);transform:rotate(180deg);}.css-eb027h{max-height:5000px;-webkit-transition:max-height 0.5s ease;transition:max-height 0.5s ease;}.css-6mllg9{-webkit-transition:all 0.5s ease;transition:all 0.5s ease;position:relative;opacity:0;}.css-6mllg9:before{content:”;background-image:linear-gradient(180deg,transparent,#ffffff);background-image:-webkit-linear-gradient(270deg,rgba(255,255,255,0),#ffffff);height:80px;width:100%;position:absolute;bottom:0px;pointer-events:none;}#masthead-bar-one{display:none;}#masthead-bar-one{display:none;}.css-1pd7fgo{background-color:white;border:1px solid #e2e2e2;width:calc(100% – 40px);max-width:600px;margin:1.5rem auto 1.9rem;padding:15px;box-sizing:border-box;}@media (min-width:740px){.css-1pd7fgo{padding:20px;width:100%;}}.css-1pd7fgo:focus{outline:1px solid #e2e2e2;}#NYT_BELOW_MAIN_CONTENT_REGION .css-1pd7fgo{border:none;padding:20px 0 0;border-top:1px solid #121212;}.css-1pd7fgo[data-truncated] .css-rdoyk0{-webkit-transform:rotate(0deg);-ms-transform:rotate(0deg);transform:rotate(0deg);}.css-1pd7fgo[data-truncated] .css-eb027h{max-height:300px;overflow:hidden;-webkit-transition:none;transition:none;}.css-1pd7fgo[data-truncated] .css-5gimkt:after{content:’See more’;}.css-1pd7fgo[data-truncated] .css-6mllg9{opacity:1;}.css-1rh1sk1{margin:0 auto;overflow:hidden;}.css-1rh1sk1 strong{font-weight:700;}.css-1rh1sk1 em{font-style:italic;}.css-1rh1sk1 a{color:#326891;-webkit-text-decoration:underline;text-decoration:underline;text-underline-offset:1px;-webkit-text-decoration-thickness:1px;text-decoration-thickness:1px;-webkit-text-decoration-color:#ccd9e3;text-decoration-color:#ccd9e3;}.css-1rh1sk1 a:visited{color:#333;-webkit-text-decoration-color:#ccc;text-decoration-color:#ccc;}.css-1rh1sk1 a:hover{-webkit-text-decoration:none;text-decoration:none;}Of the other common risk factors for severe disease, only advanced age and organ transplants increased the likelihood of hospitalization and mortality from Covid more than being inactive, the scientists found.“Being sedentary was the greatest risk factor” for severe illness, “unless someone was elderly or an organ recipient,” says Dr. Robert Sallis, a family and sports medicine doctor at the Kaiser Permanente Fontana Medical Center, who led the new study. And while “you can’t do anything about those other risks,” he says, “you can exercise.”Of course, this study, because it was observational, does not prove that exercise causes severe Covid risks to drop, but only that people who often exercise also are people with low risks of falling gravely ill. The study also did not delve into whether exercise reduces the risk of becoming infected with coronavirus in the first place.But Dr. Sallis points out that the associations in the study were strong. “I think, based on this data,” he says, “we can tell people that walking briskly for half an hour five times a week should help protect them against severe Covid-19.”A walk — or five — might be especially beneficial for people awaiting their first vaccine, he adds. “I would never suggest that someone who does regular exercise should consider not getting the vaccine. But until they can get it, I think regular exercise is the most important thing they can do to lessen their risk. And doing regular exercise will likely be protective against any new variants, or the next new virus out there.”

People who tended to be sedentary were far more likely to be hospitalized, and to die, from Covid than those who exercised regularly.More exercise means less risk of developing severe Covid, according to a compelling new study of physical activity and coronavirus hospitalizations. The study, which involved almost 50,000 Californians who developed Covid, found that those who had been the most active before falling ill were the least likely to be hospitalized or die as a result of their illness.The data were gathered before Covid vaccines became available and do not suggest that exercise can substitute in any way for immunization. But they do intimate that regular exercise — whether it’s going for a swim, walk, run or bike ride — can substantially lower our chances of becoming seriously ill if we do become infected.Scientists have known for some time that aerobically fit people are less likely to catch colds and other viral infections and recover more quickly than people who are out of shape, in part because exercise can amplify immune responses. Better fitness also heightens antibody responses to vaccines against influenza and other illnesses.But infections with the novel coronavirus are so new that little has been known about whether, and how, physical activity and fitness might affect risks for becoming ill with Covid. A few recent studies, however, have seemed encouraging. In one, which was published in February in The International Journal of Obesity, people who could walk quickly, an accepted gauge of aerobic fitness, developed severe Covid at much lower rates than sluggish walkers, even if the quick striders had obesity, a known risk factor for severe disease. In another study of older adults in Europe, greater grip strength, an indicator of general muscle health, signaled lowered risks for Covid hospitalizations.But those studies looked at indirect measures of people’s aerobic or muscular fitness and not their actual, everyday exercise habits, so they cannot tell us if getting up and moving — or staying still — changes the calculus of Covid risks.So, for the new study, which was published Tuesday in the British Journal of Sports Medicine, researchers and physicians at Kaiser Permanente Southern California, the University of California, San Diego, and other institutions decided to compare information about how often people exercised with whether they wound up hospitalized this past year because of Covid.The Kaiser Permanente health care system was well suited for this investigation, because, since 2009, it has included exercise as a “vital sign” during patient visits. In practice, this means doctors and nurses ask patients how many days each week they exercise, such as by walking briskly, and for how many minutes each time, then add that data to the patient’s medical record.Now, the researchers drew anonymized records for 48,440 adult men and women who used the Kaiser health care system, had their exercise habits checked at least three times in recent years and, in 2020, had been diagnosed with Covid-19. The researchers grouped the men and women by workout routines, with the least active group exercising for 10 minutes or less most weeks; the most active for at least 150 minutes a week; and the somewhat-active group occupying the territory in between.The researchers gathered data, too, about each person’s known risk factors for severe Covid, including their age, smoking habits, weight, and any history of cancer, diabetes, organ transplants, kidney problems and other serious, underlying conditions.Then the researchers crosschecked numbers, with arresting results. People in the least-active group, who almost never exercised, wound up hospitalized because of Covid at twice the rate of people in the most-active group, and were subsequently about two-and-a-half times more likely to die. Even compared to people in the somewhat-active group, they were hospitalized about 20 percent more often and were about 30 percent more likely to die..css-1xzcza9{list-style-type:disc;padding-inline-start:1em;}.css-rqynmc{font-family:nyt-franklin,helvetica,arial,sans-serif;font-size:0.9375rem;line-height:1.25rem;color:#333;margin-bottom:0.78125rem;}@media (min-width:740px){.css-rqynmc{font-size:1.0625rem;line-height:1.5rem;margin-bottom:0.9375rem;}}.css-rqynmc strong{font-weight:600;}.css-rqynmc em{font-style:italic;}.css-yoay6m{margin:0 auto 5px;font-family:nyt-franklin,helvetica,arial,sans-serif;font-weight:700;font-size:1.125rem;line-height:1.3125rem;color:#121212;}@media (min-width:740px){.css-yoay6m{font-size:1.25rem;line-height:1.4375rem;}}.css-1dg6kl4{margin-top:5px;margin-bottom:15px;}.css-16ed7iq{width:100%;display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-align-items:center;-webkit-box-align:center;-ms-flex-align:center;align-items:center;-webkit-box-pack:center;-webkit-justify-content:center;-ms-flex-pack:center;justify-content:center;padding:10px 0;background-color:white;}.css-pmm6ed{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-align-items:center;-webkit-box-align:center;-ms-flex-align:center;align-items:center;}.css-pmm6ed > :not(:first-child){margin-left:5px;}.css-5gimkt{font-family:nyt-franklin,helvetica,arial,sans-serif;font-size:0.8125rem;font-weight:700;-webkit-letter-spacing:0.03em;-moz-letter-spacing:0.03em;-ms-letter-spacing:0.03em;letter-spacing:0.03em;text-transform:uppercase;color:#333;}.css-5gimkt:after{content:’Collapse’;}.css-rdoyk0{-webkit-transition:all 0.5s ease;transition:all 0.5s ease;-webkit-transform:rotate(180deg);-ms-transform:rotate(180deg);transform:rotate(180deg);}.css-eb027h{max-height:5000px;-webkit-transition:max-height 0.5s ease;transition:max-height 0.5s ease;}.css-6mllg9{-webkit-transition:all 0.5s ease;transition:all 0.5s ease;position:relative;opacity:0;}.css-6mllg9:before{content:”;background-image:linear-gradient(180deg,transparent,#ffffff);background-image:-webkit-linear-gradient(270deg,rgba(255,255,255,0),#ffffff);height:80px;width:100%;position:absolute;bottom:0px;pointer-events:none;}#masthead-bar-one{display:none;}#masthead-bar-one{display:none;}.css-1pd7fgo{background-color:white;border:1px solid #e2e2e2;width:calc(100% – 40px);max-width:600px;margin:1.5rem auto 1.9rem;padding:15px;box-sizing:border-box;}@media (min-width:740px){.css-1pd7fgo{padding:20px;width:100%;}}.css-1pd7fgo:focus{outline:1px solid #e2e2e2;}#NYT_BELOW_MAIN_CONTENT_REGION .css-1pd7fgo{border:none;padding:20px 0 0;border-top:1px solid #121212;}.css-1pd7fgo[data-truncated] .css-rdoyk0{-webkit-transform:rotate(0deg);-ms-transform:rotate(0deg);transform:rotate(0deg);}.css-1pd7fgo[data-truncated] .css-eb027h{max-height:300px;overflow:hidden;-webkit-transition:none;transition:none;}.css-1pd7fgo[data-truncated] .css-5gimkt:after{content:’See more’;}.css-1pd7fgo[data-truncated] .css-6mllg9{opacity:1;}.css-1rh1sk1{margin:0 auto;overflow:hidden;}.css-1rh1sk1 strong{font-weight:700;}.css-1rh1sk1 em{font-style:italic;}.css-1rh1sk1 a{color:#326891;-webkit-text-decoration:underline;text-decoration:underline;text-underline-offset:1px;-webkit-text-decoration-thickness:1px;text-decoration-thickness:1px;-webkit-text-decoration-color:#ccd9e3;text-decoration-color:#ccd9e3;}.css-1rh1sk1 a:visited{color:#333;-webkit-text-decoration-color:#ccc;text-decoration-color:#ccc;}.css-1rh1sk1 a:hover{-webkit-text-decoration:none;text-decoration:none;}Of the other common risk factors for severe disease, only advanced age and organ transplants increased the likelihood of hospitalization and mortality from Covid more than being inactive, the scientists found.“Being sedentary was the greatest risk factor” for severe illness, “unless someone was elderly or an organ recipient,” says Dr. Robert Sallis, a family and sports medicine doctor at the Kaiser Permanente Fontana Medical Center, who led the new study. And while “you can’t do anything about those other risks,” he says, “you can exercise.”Of course, this study, because it was observational, does not prove that exercise causes severe Covid risks to drop, but only that people who often exercise also are people with low risks of falling gravely ill. The study also did not delve into whether exercise reduces the risk of becoming infected with coronavirus in the first place.But Dr. Sallis points out that the associations in the study were strong. “I think, based on this data,” he says, “we can tell people that walking briskly for half an hour five times a week should help protect them against severe Covid-19.”A walk — or five — might be especially beneficial for people awaiting their first vaccine, he adds. “I would never suggest that someone who does regular exercise should consider not getting the vaccine. But until they can get it, I think regular exercise is the most important thing they can do to lessen their risk. And doing regular exercise will likely be protective against any new variants, or the next new virus out there.”

Older people with mild cognitive impairment showed improvements in brain blood flow and memory after a yearlong aerobic exercise program.Brisk walking improves brain health and thinking in aging people with memory impairments, according to a new, yearlong study of mild cognitive impairment and exercise. In the study, middle-aged and older people with early signs of memory loss raised their cognitive scores after they started walking frequently. Regular exercise also amplified the healthy flow of blood to their brains. The changes in their brains and minds were subtle but consequential, the study concludes, and could have implications not just for those with serious memory problems, but for any of us whose memories are starting to fade with age.Most of us, as we get older, will find that our ability to remember and think dulls a bit. This is considered normal, if annoying. But if the memory loss intensifies, it may become mild cognitive impairment, a medical condition in which the loss of thinking skills grows obvious enough that it becomes worrisome to you and others around you. Mild cognitive impairment is not dementia, but people with the condition are at heightened risk of developing Alzheimer’s disease later.Scientists have not yet pinpointed the underlying causes of mild cognitive impairment, but there is some evidence that changes in blood flow to the brain can contribute. Blood carries oxygen and nutrients to brain cells and if that stream sputters, so can the vitality of neurons.Unfortunately, many people experience declines in the flow of blood to their brains with age, when their arteries stiffen and hearts weaken.But the good news is that exercise can increase brain blood flow, even when exercisers are not moving. In a 2013 neurological study, the brains of physically active older men showed much better blood saturation than those of sedentary men, even when everyone was quietly resting. The greater brain blood flow in people who exercise also is associated with better scores on tests of memory and thinking than among sedentary people.But these studies generally focused on people whose brains and cognition were relatively normal. Exercise bulked up, for them, what already was reasonably sound. Far less is known about whether physical activity similarly benefits the blood flow, brains and thinking of people who are starting to experience more serious memory loss.So, for the new study, which was published this month in the Journal of Alzheimer’s Disease, researchers at the University of Texas Southwestern Medical Center in Dallas and other institutions asked a group of 70 sedentary men and women, aged 55 or older and diagnosed with mild cognitive impairment, to start moving more.They first brought everyone into the lab and tested their current health, cognitive function and aerobic fitness. Then, using advanced ultrasounds and other techniques, they measured the stiffness of their carotid artery, which carries blood to the brain, and the amount of blood flowing to and through their brains.Finally, they divided the volunteers into two groups. One began a program of light stretching and toning exercises, to serve as an active control group. The others started to exercise aerobically, mostly by walking on treadmills at the lab, and then, after a few weeks, outside on their own. The exercisers were asked to keep their exertions brisk, so that their heart rates and breathing rose noticeably. (They could swim, ride bikes or do ballroom dancing if they chose, but almost everyone walked.) The control group kept their heart rates low.Everyone in both groups worked out three times a week at first, for about half an hour and under supervision. They then added sessions on their own, until after six months, they were completing about five workouts most weeks. This program continued for a year, in total. About 20 volunteers dropped out over that time, mostly from the walking group.Then the volunteers returned to the lab for a repeat of the original tests, and the researchers compared results. To no one’s surprise, the exercise group was more fit, with higher aerobic capacity, while the stretchers’ endurance had not budged. The aerobic exercise group also showed much less stiffness in their carotid arteries and, in consequence, greater blood flow to and throughout their brains.Perhaps most important, they also performed better now than the stretch-and-tone group on some of the tests of executive function, which are thinking skills involved in planning and decision-making. These tend to be among the abilities that decline earliest in dementia.Interestingly, though, both groups had raised their scores slightly on most tests of memory and thinking, and to about the same extent. In effect, getting up and moving in any way — and perhaps also interacting socially with people at the lab — appeared to have burnished thinking skills and helped to stave off accelerating declines.Still, the researchers believe that over a longer period of time, brisk walking would result in greater cognitive gains and less memory decline than gentle stretching, says Rong Zhang, a neurology professor at UT Southwestern Medical Center, who oversaw the new study.“It probably takes more time” than a year for the improved brain blood flow to translate into improved cognition, he says. He and other researchers are planning larger, longer-lasting studies to test that idea, he says. They hope, too, to investigate how more — or fewer — sessions of exercise each week might aid the brain, and whether there might be ways to motivate more of the volunteers to stick with an exercise program.For now, though, he believes the group’s findings serve as a useful reminder that moving changes minds. “Park farther away” when you shop or commute, he says. “Take the stairs,” and try to get your heart rate up when you exercise. Doing so, he says, may help to protect your lifelong ability to remember and think.

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.

AdvertisementContinue reading the main storySupported byContinue reading the main storyPhys EdGetting to the Bottom of the Runner’s HighFor years we’ve been crediting endorphins, but it’s really about the endocannabinoids.Credit…Kevin Hagen for The New York TimesMarch 10, 2021, 5:00 a.m. ETWe can stop crediting endorphins, the natural opioid painkillers produced by our bodies, for the floaty euphoria we often feel during aerobic exercise, according to a nifty new study of men, women and treadmills. In the study, runners developed a gentle intoxication, known as a runner’s high, even if researchers had blocked their bodies’ ability to respond to endorphins, suggesting that those substances could not be behind the buzz. Instead, the study suggests, a different set of biochemicals resembling internally homegrown versions of cannabis, better known as marijuana, are likely to be responsible.The findings expand our understanding of how running affects our bodies and minds, and also raise interesting questions about why we might need to be slightly stoned in order to want to keep running.In surveys and studies of experienced distance runners, most report developing a mellow runner’s high at least sometimes. The experience typically is characterized by loose-limbed blissfulness and a shedding of anxiety and unease after half an hour or so of striding. In the 1980s, exercise scientists started attributing this buzz to endorphins, after noticing that blood levels of the natural painkillers rise in people’s bloodstreams when they run.More recently, though, other scientists grew skeptical. Endorphins cannot cross the blood-brain barrier, because of their molecular structure. So, even if runners’ blood contains extra endorphins, they will not reach the brain and alter mental states. It also is unlikely that the brain itself produces more endorphins during exercise, according to animal studies.Endocannabinoids are a likelier intoxicant, these scientists believed. Similar in chemical structure to cannabis, the cannabinoids made by our bodies surge in number during pleasant activities, such as orgasms, and also when we run, studies show. They can cross the blood-brain barrier, too, making them viable candidates to cause any runner’s high.A few past experiments had strengthened that possibility. In one notable 2012 study, researchers coaxed dogs, people and ferrets to run on treadmills, while measuring their blood levels of endocannabinoids. Dogs and humans are cursorial, meaning possessed of bones and muscles well adapted to distance running. Ferrets are not; they slink and sprint but rarely cover loping miles, and they did not produce extra cannabinoids while treadmill running. The dogs and people did, though, indicating that they most likely were experiencing a runner’s high and it could be traced to their internal cannabinoids.That study did not rule out a role for endorphins, however, as Dr. Johannes Fuss realized. The director of the Human Behavior Laboratory at the University Medical Center Hamburg-Eppendorf in Germany, he and his colleagues had long been interested in how various activities affect the inner workings of the brain, and after reading the ferret study and others, thought they might look more closely into the runner’s high.They began with mice, which are eager runners. For a 2015 study, they chemically blocked the uptake of endorphins in the animals’ brains and let them run, then did the same with the uptake of endocannabinoids. When their endocannabinoid system was turned off, the animals ended their runs just as anxious and twitchy as they had been at the start, suggesting that they had felt no runner’s high. But when their endorphins were blocked, their behavior after running was calmer, relatively more blissed-out. They seemed to have developed that familiar, mild buzz, even though their endorphin systems had been inactivated.Mice emphatically are not people, though. So, for the new study, which was published in February in Psychoneuroendocrinology, Dr. Fuss and his colleagues set out to replicate the experiment, to the extent possible, in humans. Recruiting 63 experienced runners, male and female, they invited them to the lab, tested their fitness and current emotional states, drew blood and randomly assigned half to receive naloxone, a drug that blocks the uptake of opioids, and the rest, a placebo. (The drug they had used to block endocannabinoids in mice is not legal in people, so they could not repeat that portion of the experiment.)The volunteers then ran for 45 minutes and, on a separate day, walked for the same amount of time. After each session, the scientists drew blood and repeated the psychological tests. They also asked the volunteers whether they thought they had experienced a runner’s high.Most said yes, they had felt buzzed during the run, but not the walk, with no differences between the naloxone and placebo groups. All showed increases, too, in their blood levels of endocannabinoids after running and equivalent changes in their emotional states. Their euphoria after running was greater and their anxiety less, even if their endorphin system had been inactivated.Taken as a whole, these findings are a blow to endorphins’ image. “In combination with our research in mice,” Dr. Fuss says, “these new data rule out a major role for endorphins” in the runner’s high.The study does not explain, though, why a runner’s high exists at all. There was no walker’s high among the volunteers. But Dr. Fuss suspects the answer lies in our evolutionary past. “When the open savannas stretched and forests retreated,” he says, “it became necessary for humans to hunt wild animals by long-distance running. Under such circumstances, it is beneficial to be euphoric during running,” a sensation that persists among many runners today, but with no thanks due, it would seem, to endorphins.AdvertisementContinue reading the main story

AdvertisementContinue reading the main storySupported byContinue reading the main storyPhys EdGetting to the Bottom of the Runner’s HighFor years we’ve been crediting endorphins, but it’s really about the endocannabinoids.Credit…Kevin Hagen for The New York TimesMarch 10, 2021, 5:00 a.m. ETWe can stop crediting endorphins, the natural opioid painkillers produced by our bodies, for the floaty euphoria we often feel during aerobic exercise, according to a nifty new study of men, women and treadmills. In the study, runners developed a gentle intoxication, known as a runner’s high, even if researchers had blocked their bodies’ ability to respond to endorphins, suggesting that those substances could not be behind the buzz. Instead, the study suggests, a different set of biochemicals resembling internally homegrown versions of cannabis, better known as marijuana, are likely to be responsible.The findings expand our understanding of how running affects our bodies and minds, and also raise interesting questions about why we might need to be slightly stoned in order to want to keep running.In surveys and studies of experienced distance runners, most report developing a mellow runner’s high at least sometimes. The experience typically is characterized by loose-limbed blissfulness and a shedding of anxiety and unease after half an hour or so of striding. In the 1980s, exercise scientists started attributing this buzz to endorphins, after noticing that blood levels of the natural painkillers rise in people’s bloodstreams when they run.More recently, though, other scientists grew skeptical. Endorphins cannot cross the blood-brain barrier, because of their molecular structure. So, even if runners’ blood contains extra endorphins, they will not reach the brain and alter mental states. It also is unlikely that the brain itself produces more endorphins during exercise, according to animal studies.Endocannabinoids are a likelier intoxicant, these scientists believed. Similar in chemical structure to cannabis, the cannabinoids made by our bodies surge in number during pleasant activities, such as orgasms, and also when we run, studies show. They can cross the blood-brain barrier, too, making them viable candidates to cause any runner’s high.A few past experiments had strengthened that possibility. In one notable 2012 study, researchers coaxed dogs, people and ferrets to run on treadmills, while measuring their blood levels of endocannabinoids. Dogs and humans are cursorial, meaning possessed of bones and muscles well adapted to distance running. Ferrets are not; they slink and sprint but rarely cover loping miles, and they did not produce extra cannabinoids while treadmill running. The dogs and people did, though, indicating that they most likely were experiencing a runner’s high and it could be traced to their internal cannabinoids.That study did not rule out a role for endorphins, however, as Dr. Johannes Fuss realized. The director of the Human Behavior Laboratory at the University Medical Center Hamburg-Eppendorf in Germany, he and his colleagues had long been interested in how various activities affect the inner workings of the brain, and after reading the ferret study and others, thought they might look more closely into the runner’s high.They began with mice, which are eager runners. For a 2015 study, they chemically blocked the uptake of endorphins in the animals’ brains and let them run, then did the same with the uptake of endocannabinoids. When their endocannabinoid system was turned off, the animals ended their runs just as anxious and twitchy as they had been at the start, suggesting that they had felt no runner’s high. But when their endorphins were blocked, their behavior after running was calmer, relatively more blissed-out. They seemed to have developed that familiar, mild buzz, even though their endorphin systems had been inactivated.Mice emphatically are not people, though. So, for the new study, which was published in February in Psychoneuroendocrinology, Dr. Fuss and his colleagues set out to replicate the experiment, to the extent possible, in humans. Recruiting 63 experienced runners, male and female, they invited them to the lab, tested their fitness and current emotional states, drew blood and randomly assigned half to receive naloxone, a drug that blocks the uptake of opioids, and the rest, a placebo. (The drug they had used to block endocannabinoids in mice is not legal in people, so they could not repeat that portion of the experiment.)The volunteers then ran for 45 minutes and, on a separate day, walked for the same amount of time. After each session, the scientists drew blood and repeated the psychological tests. They also asked the volunteers whether they thought they had experienced a runner’s high.Most said yes, they had felt buzzed during the run, but not the walk, with no differences between the naloxone and placebo groups. All showed increases, too, in their blood levels of endocannabinoids after running and equivalent changes in their emotional states. Their euphoria after running was greater and their anxiety less, even if their endorphin system had been inactivated.Taken as a whole, these findings are a blow to endorphins’ image. “In combination with our research in mice,” Dr. Fuss says, “these new data rule out a major role for endorphins” in the runner’s high.The study does not explain, though, why a runner’s high exists at all. There was no walker’s high among the volunteers. But Dr. Fuss suspects the answer lies in our evolutionary past. “When the open savannas stretched and forests retreated,” he says, “it became necessary for humans to hunt wild animals by long-distance running. Under such circumstances, it is beneficial to be euphoric during running,” a sensation that persists among many runners today, but with no thanks due, it would seem, to endorphins.AdvertisementContinue reading the main story

AdvertisementContinue reading the main storySupported byContinue reading the main storyPhys EdHow Exercise Enhances Aging BrainsSedentary, older adults who took aerobic dance classes twice a week showed improvements in brain areas critical for memory and thinking.Volunteers who participated in pre-pandemic dance classes in Newark, N.J., showed improvements in memory centers in the brain.Credit…Rutgers UniversityMarch 3, 2021, 5:00 a.m. ETExercise can change how crucial portions of our brain communicate as we age, improving aspects of thinking and remembering, according to a fascinating new study of aging brains and aerobic workouts. The study, which involved older African-Americans, finds that unconnected portions of the brain’s memory center start interacting in complex and healthier new ways after regular exercise, sharpening memory function.The findings expand our understanding of how moving molds thinking and also underscore the importance of staying active, whatever our age.The idea that physical activity improves brain health is well established by now. Experiments involving animals and people show exercise increases neurons in the hippocampus, which is essential for memory creation and storage, while also improving thinking skills. In older people, regular physical activity helps slow the usual loss of brain volume, which may help to prevent age-related memory loss and possibly lower the risk of dementia.There have been hints, too, that exercise can alter how far-flung parts of the brain talk among themselves. In a 2016 M.R.I. study, for instance, researchers found that disparate parts of the brain light up at the same time among collegiate runners but less so among sedentary students. This paired brain activity is believed to be a form of communication, allowing parts of the brain to work together and improve thinking skills, despite not sharing a physical connection. In the runners, the synchronized portions related to attention, decision making and working memory, suggesting that running and fitness might have contributed to keener minds.But those students were young and healthy, facing scant imminent threat of memory loss. Little was known yet about whether and how exercise might alter the communications systems of creakier, older brains and what effects, if any, the rewiring would have on thinking.So, for the new study, which was published in January in Neurobiology of Learning and Memory, Mark Gluck, a professor of neuroscience at Rutgers University in Newark, N.J., and his colleagues decided to see what happened inside the brains and minds of much older people if they began to work out.In particular, he wondered about their medial temporal lobes. This portion of the brain contains the hippocampus and is the core of our memory center. Unfortunately, its inner workings often begin to sputter with age, leading to declines in thinking and memory. But Dr. Gluck suspected that exercise might alter that trajectory.Helpfully, as the director of the Aging & Brain Health Alliance at Rutgers, he already was leading an ongoing exercise experiment. Working with local churches and community centers, he and his collaborators previously had recruited sedentary, older African-American men and women from the Newark area. The volunteers, most of them in their 60s, visited Dr. Gluck’s lab for checks of their health and fitness, along with cognitive testing. A few also agreed to have their brain activity scanned.Some then started working out, while others opted to be a sedentary control group. All shared similar fitness and memory function at the start. The exercise group attended hourlong aerobic dance classes twice a week at a church or community center for 20 weeks.Now, Dr. Gluck and his research associate Neha Sinha, along with other colleagues, invited 34 of those volunteers who had completed an earlier brain scan to return for another. Seventeen of them had been exercising in the meantime; the rest had not. The groups also repeated the cognitive tests.Then the scientists started comparing and quickly noticed subtle differences in how the exercisers’ brains operated. Their scans showed more-synchronized activity throughout their medial temporal lobes than among the sedentary group, and this activity was more dynamic. Portions of the exercisers’ lobes would light up together and then, within seconds, realign and light up with other sections of the lobe. Such promiscuous synchronizing indicates a kind of youthful flexibility in the brain, Dr. Gluck says, as if the circuits were smoothly trading dance partners at a ball. The exercisers’ brains would “flexibly rearrange their connections,” he says, in a way that the sedentary group’s brains could not.Just as important, those changes played out in people’s thinking and memories. The exercisers performed better than before on a test of their ability to learn and retain information and apply it logically in new situations. This kind of agile thinking involves the medial temporal lobe, Dr. Gluck says, and tends to decline with age. But the older exercisers scored higher than at the start, and those whose brains displayed the most new interconnections now outperformed the rest.This study involved older African-Americans, though, a group that is underrepresented in health research but may not be representative of all aging people. Still, even with that caveat, “it seems that neural flexibility” gained by exercising a few times a week “leads directly to memory flexibility,” Dr. Gluck says.AdvertisementContinue reading the main story