A mere four seconds of exercise in total, repeated some thirty times, may be all that many of us need to develop and maintain our fitness, strength and physical power, according to an inspiring study of the effects of superfast exercise. The findings echo other recent studies that show that four-second interval exercises beneficially affect the metabolism and the muscles in adults of various ages. But perhaps they also highlight new concerns about what we lose if we make our workouts too brief.
Almost anyone with even a passing interest in physical activity and health has heard of high intensity interval training or HIIT. A typical HIIT workout involves short, repeated bursts of strenuous effort interspersed with rest periods.
For generations, athletes have used this feature to increase their speed and performance. But for most of us, the main attraction of HIIT is its short duration. In previous studies, intense interval exercise that ranges in duration from four minutes or even less improved aspects of exercise. health and fitness as much as or to a greater extent than much longer sessions of gentler continuous exercise such as light jogging or walking. For HIIT fans, high intensity workouts often represent their main or only form of exercise.
However, the optimal duration of each exercise period remains uncertain. Most exercise scientists agree that each period of physical activity it must vigorously stimulate and force our hearts, lungs, and muscles, causing them to remodel themselves in a beneficial way. But the intense exercise they shouldn’t be so tiring that we can’t finish them or we never want to do them again at the end of physical activity. Each interval exercise period should essentially be as tiring and tolerable as possible.
To Edward Coyle, teacher of kinesiology and health education at the University of Texas at Austin, this meant an ideal activity period of about four seconds. He and his colleagues reached that number after studying professional athletes in form. During physiological tests in Coyle’s lab, athletes achieved extraordinary speed and power while pedaling special stationary bikes that feature heavy, no-resistance handlebars. (Coyle has a stake in the company that makes the bikes, but says his financial involvement does not affect his lab’s research results.)
In about two seconds of pedaling on these exclusive bikes, the athletes reached a maximum level of aerobic effort and potency. Coyle and his colleagues found that this was an effort athletes could sustain for a brief period, but repeat often, after a few seconds of recovery break between them.
For the rest of us who are not fit professional athletes, it may take more physical activity to achieve our maximum aerobic effort and power development during similar cycling intervals, Coyle concluded. But even doubling the time would only give four seconds.
But could four seconds of exercise really be enough physical activity? To try to figure this out, he and his colleagues set up a series of recent experiments.
During the first study, published last year, they asked college students to complete five repetitions of four-second exercises on specially designed bicycles every hour during an eight-hour workday. They found that the volunteers metabolized fat much better the next day than if they had sat there all day without exercising.
Likewise, a larger, longer-term study involving older, out-of-fit adults showed that regular exercise lasting four seconds, during which volunteers repeated these tiny but intense periods of activity on bicycles, at least 15 times per session, they significantly increased their aerobic fitness and their leg muscle mass after eight weeks.
However, whether training at four-second intervals would significantly improve physical fitness and muscle power in people who start activities in good shape was not yet clear. So for the new study, which was published in July in the academic journal Medicine & Science in Sports & Exercise, Coyle and his colleagues persuaded 11 healthy, non-sedentary young men to go to the lab and exercise in 30 repetitions of four seconds of maximal effort on the bikes, with at least 15 seconds of rest in between. The volunteers completed three sessions of these intervals each week for eight weeks, totaling 48 minutes of exercise over the two months. They didn’t exercise any other way during this time.
During that time, they added 13 percent to a crucial aerobic fitness measure and 17 percent to their muscle power, measured by how many watts they produced while pedaling the bike, the researchers found.
These results suggest that a few seconds of strenuous exertion “certainly provide enough stimulation” to strengthen already robust hearts and muscles, Coyle said. In practice, he continued, this is perhaps the same as running uphill repeatedly for four seconds at a time or climbing steps two or three at a time in four-second “explosions”.
However, he stressed that the study’s implications are also a warning. Other research, including his earlier study of students, suggests that being sedentary for long periods can have detrimental effects on metabolic health, undermining the benefits of high-intensity exercise. So if you do several exercises at four-second intervals in the morning and then sit almost still for the rest of your day, you might end up with metabolic problems related to being sedentary, despite those four-second bursts of exertion earlier in the day. .
“In general, it will be a good idea to get up and move throughout the day,” he said, “and sometimes move in a physically intense way as well,” even if it takes as little as four seconds. / TRANSLATION OF ROMINA CACIA
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