Four-second interval workouts may be all it takes to maintain fitness and strength

Just four seconds of total exercise repeated two or three dozen times could, according to one inspiring new study the power of super-fast workouts.

The results build on other, more recent studies that show that four-second interval training has a positive effect on metabolism and muscles in adults of different ages. But they can also raise new concerns about what we’re missing out on if we miss out on our workouts.

Almost everyone with even a passing interest in exercise and health has by now heard of high-intensity interval training, or HIIT. Typical HIIT workout involves repetitive, brief bursts of strenuous exertion known as intervals, interrupted by periods of rest.

For generations, athletes have been training regularly to increase their speed and performance. But for most of us, the main appeal of HIIT lies in its brevity. In previous studies, workouts with intense intervals of four minutes or even less improved health and fitness aspects to the same or greater extent than much longer sessions of continuous, gentler exercise such as jogging or walking. For HIIT fans, the high-intensity workouts are often their primary or only form of training.

The ideal length of the individual intervals, however, remains uncertain. Most exercise scientists agree that an interval should intensely stimulate and pressurize our heart, lungs, and muscles to get them to transform themselves in beneficial ways. But workouts that are so intense shouldn’t be so strenuous that we don’t want to end the intervals or never want to train again afterwards. Essentially, each interval should be as strenuous and as bearable as possible.

Wink number

For Edward Coyle, professor of kinesiology and health education at the University of Texas at Austin, that meant an interval sweet spot of about four seconds. He and his colleagues got that wink after studying fit professional athletes. During the physiological tests in Coyle’s lab, the athletes generated gigantic speed and power while pedaling on specialized stationary bikes that had a heavy flywheel and no drag. (Coyle has an interest in the company that makes the bicycles, but says his financial stake doesn’t affect his lab’s research.)

Coyle and colleagues found that within about two seconds of pedaling these unique bikes, the athletes reached a maximal, maximal level of aerobic exertion and power output, an exertion they could sustained briefly but could repeat many times with a few seconds of recovery Time in between.

The rest of us who aren’t fit professional athletes may need more time to get our maximum aerobic effort and power output during similar cycling intervals, Coyle mused. But only four seconds would be twice as long.

Could four-second intervals really provide enough exercise?

To find out, he and his colleagues carried out a series of new experiments.

During the first study, published last year, they asked college students to do five repetitions of four-second intervals every hour on the specially designed bikes for an eight-hour work day. They found that the subjects metabolized fat much better the next day than if they sat without exercising all day.

Similarly, a broader, longer-term study involving older adults showed that regular four-second interval workouts, where volunteers repeated the tiny but intense intervals on the bike at least 15 times per workout, reduced their aerobic fitness and leg muscle mass by eight Weeks.

But it was not yet clear whether a four-second interval workout would sensibly improve the fitness and muscle strength of people who started in good shape. For the new study, published in Medicine & Science in Sports & Exercise, Coyle and colleagues convinced 11 healthy, active young men and women to come into the lab and torment themselves through 30 repetitions of the four seconds, all – Exertion on the bikes with a break of at least 15 seconds in between. The volunteers completed three sessions of these intervals each week for eight weeks for a total of 48 minutes of training over the two months. You did not do any other sport during this time.

Muscle strength

During this time, they contributed 13 percent to an important aerobic fitness exercise and 17 percent to their muscle strength, measured by how many watts they produced when pedaling the bike, the researchers found.

These results suggest that a few seconds of strenuous exertion “definitely provides enough stimulus” to strengthen already resilient hearts and muscles, Coyle said. In practice, he continued, this could mean sprinting uphill for four seconds over and over, or taking four-second jumps up two or three flights of stairs at a time.

However, the implications of the study are also cautionary, he stressed. Other research, including his previous study with college students, suggests prolonged range of motion could have detrimental effects on metabolic health and undermine the benefits of high-intensity exercise. So, if you go through several four-second intervals in the morning and then sit almost motionless for the remaining seconds of your day, you can end up with sedentary-related metabolic problems despite those earlier four-second bursts of movement.

“In general, it is a good idea to get up and move around all day,” he said, “and then sometimes exercise vigorously,” even if it takes as little as four seconds. – New York Times

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