The best exercise for many of us may not be the shortest, according to a provocative new study comparing the health benefits of short, intense interval workouts with those of longer, gentler workouts.
The study, published in Medicine & Science in Sports & Exercise, concludes that each approach to exercise has its advantages, but that the effects on blood pressure, the body fat and other aspects of metabolism may be higher after standard workouts, half an hour and moderate, than quick interval workouts.
As we who follow fitness know, high intensity interval training, or HIIT (High Intensity Interval Training) is seductive, fashionable, and a frequent topic in this column, as well as in exercise science.
HIIT, a mix of extremely short periods of intense exercise followed by a minute or two of rest, it’s fast and powerful, and studies show that a few minutes – or even seconds – of interval training can improve health and fitness. longevity of people over time.
But there are still many unanswered questions about the relative advantages of quick intervals over more traditional sustained aerobic workouts, such as brisk walking, running, or bikingEspecially if someone only engages in one type of exercise and not the other.
Frequent moderate exercise is linked to improvements in blood pressure and glucose control. Photo Shutterstock.
So recently, exercise scientists at the University of Guelph in Ontario began studying how people’s bodies change if they train exclusively with intervals or standard and moderate training, following current exercise guidelines.
Interestingly, many previous studies comparing short HIIT routines and longer moderate workouts did not adhere to formal exercise recommendations because scientists wanted to match the frequency of workouts or other measures. Thus, the volunteers in these studies used to exercise three times a week, either completing a few minutes of HIIT or half an hour of brisk walking.
But exercise guidelines for each type of activity differ. Medical and sports groups suggest that we do not train at intervals more than three times a week, to avoid the overexertion of muscles and cardiovascular systems, which means that if we exercise only with HIIT, we will be inactive four days a week or so. Comparable guidelines for moderate exercise suggest getting out and moving at least five times a week and for at least 30 minutes each time.
So the Guelph scientists thought: what if people do HIIT three days a week and don’t exercise any other type of exercise the other four, or train moderately five times a week?
To find out, they first recruited 23 sedentary adult men with overweight. They did not include women, out of concern that menstrual cycles would affect metabolic outcomes, but they hope to include women in some larger future experiment.
They invited these men to the lab, measured their fitness, body composition and blood pressure, and asked them to drink shakes loaded with large amounts of fat to see how their metabolism responded to the nutrient. They were also fitted with blood sugar monitors to wear home for a week to measure their daily blood sugar control, a measure of metabolic health.
They then asked half the men to start interval training three times a week on stationary bikes in the lab, pedaling as hard as possible for 30 seconds, resting for two minutes and repeating that sequence four to six times.
The other men started a typical moderate exercise program, biking in the lab five times a week at a pace they could comfortably maintain. for 30 to 40 minutes.
Over the course of the next six weeks, the HIIT group pedaled vigorously for a total of less than an hour, while the moderate intensity group exercised for at least 2.5 hours each week for the same period.
At the end of the six weeks, both groups returned to the laboratory for further tests, after which the scientists examined the results for disparities. They found many.
Most of the men were fitter, and more or less to the same extent, regardless of the exercise they had done. But only those in the moderate exercise group had shed a lot of fat body, had improved their blood pressure or were better able to metabolize the extra fat from the creamy shake.
Perhaps the most interesting thing is that everyone’s blood sugar control at home was better only on the days they exercised, that is, three times a week for those who did HIIT and five times a week for the moderate group. The rest of the days, blood sugar levels tended to rise.
Taken together, the results indicate that intervals and traditional exercise alter our bodies in divergent ways, and we may want to consider what we hope to achieve with exercise when choosing the best way to do it, says Jamie Burr, Professor at the University of Guelph, who conducted the new study with his graduate student Heather Petrick and other colleagues.
“All exercise is good”Burr said. But “there are nuances.” Frequent, almost daily moderate exercise may be preferable for improving blood pressure and continuous blood sugar control, compared to infrequent intervals, he says, while a little HIIT is likely to get you in shape with same efficiency as hours and hours of pedaling easier or a similar effort.
Of course, this study was small-scale and short-term, and only overweight and out of shape men participated in it, so we cannot be sure that the results apply to the rest of the population. But the main lesson seems to be widely applicable.
“Move often,” Burr said, meaning if you do HIIT today, you walk tomorrow.
Por Gretchen Reynolds ©The New York Times