For fitness intensity matters

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Exerting yourself vigorously may have unique payoffs, compared with less strenuous exercise. (Thinkstock) Exerting yourself vigorously may have unique payoffs, compared with less strenuous exercise. (Thinkstock)
SummaryLesson learnt from 2013 studies: Vigorous workout most effective.

This year, exercise science expanded and fine-tuned our understanding of how physical activity affects our brains, joints, hearts, and even genes, beginning before birth and continuing throughout our lifespans, which can be lengthened, it seems, by exercise, especially if we pick up the pace.

This year’s fitness news was variously enlightening, validating (if, like me, you never bothered cooling down after a workout anyway), and practical (DIY concussion testing, anyone?). It was also occasionally deflating, at least if you hoped that barefoot running invariably would reduce the risk of injury, gentle exercise would quash your appetite, or training for a marathon would automatically exempt you from being a couch potato.

But the lesson that seemed to emerge most persistently from the fitness-related studies published this year was that intensity matters, especially if you wish to complete your workout quickly. The most popular column that I wrote this year, by a wide margin, detailed ‘The scientific 7-minute workout’, a concept that appealed, I have no doubt, because the time commitment was so slight. But the vigour required was considerable; to gain health benefits from those seven minutes, you needed to maintain a thumping heart rate and spray sweat droplets around the room.

Almost halving the time spent exercising was also effective, a later and likewise popular column showed. In that study, out-of-shape volunteers who ran on a treadmill for a mere four minutes three times a week for 10 weeks raised their maximal oxygen uptake, or endurance capacity, by about 10 per cent and significantly improved their blood sugar control and blood pressure profiles.

The results undercut a common excuse for skipping workouts. “One of the main reasons people give” for not exercising is that they don’t have time, said Arnt Erik Tjonna, a postdoctoral fellow at the Norwegian University of Science and Technology, who led the study.

But they emphasise, too, the potency of hard effort. The volunteers ran at 90 per cent of their maximum aerobic capacity for those four minutes, a level that is frankly unpleasant. But, in four minutes, they were done.

There were other hints throughout the year that exerting yourself vigorously may have unique payoffs, compared with less strenuous exercise. In a study that I wrote about a few weeks ago, for instance, people who walked briskly, at a pace of 17 minutes per mile or less, generally lived longer than those men and women who strolled during their walks, at a pace of 20 minutes per mile or slower, although the study was not designed to determine why the intensity of the exercise mattered.

And in September, I wrote about two studies showing that strenuous exercise blunted volunteers’ appetites after workouts more effectively than longer sessions of easy exercise did. The studies were small, though, and involved only young-ish, overweight men. Whether the results are applicable to other people, including those of us who are not male, requires additional experiments.

Meanwhile, other studies that I wrote about this year emphasise how pervasive the impacts of any amount and type of exercise can be. One of my favorite experiments of 2013 detailed how rodents that ran on wheels for several weeks responded far better to stressful situations than sedentary animals, in large part, it seems, because their brains contained specialised cells that dampened unnecessary anxiety. At a molecular level, the runners’ brains were calmer than those of their sedentary lab mates.

But perhaps the most remarkable studies of the year examined the effect of exercise on our DNA. In several experiments, which I wrote about in July, scientists found that exercise reshapes genes in human cells, changing how atoms attach to the outside of individual portions of our DNA. As a result, I wrote, the behavior of the gene changes.

In one of the studies, researchers found that six months of moderate exercise profoundly remodelled genes related to the risk for diabetes and heart disease. But for those of us too impatient to wait six months, the other study found that a single session of bike riding altered genes in volunteers’ muscle cells. The effects showed up whether the pedaling was easy or strenuous, but, in line with so much of this year’s exercise science, were more pronounced when cyclists rode vigorously.

Still, for everyone, as one of the scientists told me, the studies are an important and inspirational reminder of “the robust effect exercise can have on the human body, even at the level of our DNA”.

Is it good to sweat?

Are there any health benefits associated with more sweating during a workout?

“There’s this entrenched idea that it’s good to ‘sweat things out’,” said Oliver Jay, an associate professor of exercise physiology and director of the Thermal Ergonomics Laboratory at the University of Ottawa in Canada, and by extension, that sweating heavily during exercise is somehow healthier than misting daintily. But in fact, “sweating, per se, provides no health benefits,” Dr Jay said, apart from preventing overheating. The benefits derive from the exercise itself, and the more intense, generally, the greater the health benefits.

Core temperature rises during prolonged and vigorous physical activity, though, and your body must shed that heat. It does so in large part by sweating. The more vigorously you exert yourself, the more internal heat you produce, and the more you must sweat. Such strenuous exercise improves health through many different physiological mechanisms. But perspiring, in and of itself, does not provide or amplify those effects, Dr Jay said.

That situation doesn’t change if you’re sweating due to a hot environment. “Sweat is sweat,” he said. As a rule of thumb, drink when you feel thirsty, so that sweating doesn’t become actually unhealthy.

GRETCHEN REYNOLDS

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