The study shows that as little 2 minutes of high-intensity exercise four times a day had a more beneficial effect on teens' health measures than moderate intensity activity.
Researchers at the University of Exeter in the UK concluded that when adolescents accumulate exercise over the day, short bouts of intense activity have a more beneficial effect on health than shorts bouts of less intense activity.
Reporting in the journal Metabolism: Clinical and Experimental, they show how as little 2 minutes of high-intensity exercise four times a day had a more beneficial effect on blood sugar levels, fat metabolism and blood pressure - measured after eating a fatty meal - than the same amount of moderate intensity exercise.
Senior author Dr. Alan Barker, a lecturer in pediatric exercise and health at Exeter, says:
"Children and adolescents tend to perform brief bouts of exercise. This study shows that the intensity of this pattern of exercise is important, with high-intensity providing superior health benefits than moderate-intensity exercise."
For the study, the team examined 19 teenagers' blood sugar, systolic blood pressure and fat oxidation at regular intervals over 3 days, during which the youngsters consumed a high fat milkshake for breakfast and lunch. The participants were 9 male and 10 female 13-year-olds.
During the 3 days, the participants completed three different exercise patterns in random order: rest, four bouts of high-intensity, and four bouts of moderate intensity exercise performed on exercise bikes. On exercise days, the bouts were done 2 hours apart.
During the bouts of exercise, the participants performed the same amount of work - so the researchers could examine the effect of intensity alone.
Adds to growing evidence that high-intensity exercise is more beneficial to heart health
The authors found that neither type of exercise changed levels of excess fat in the blood. However, brief bouts of high-intensity exercise - but not moderate-intensity exercise - reduced blood sugar and systolic blood pressure, and increased fat metabolism in the teen boys and girls.
"The intensity of accumulated exercise may therefore have important implications for health outcomes in youth."
The study adds to a growing body of evidence that suggests accumulating short bursts of high-intensity exercise may be more important for heart health than accumulating moderate intensity exercise. This is important because heart disease is the leading cause of death worldwide, and the drivers start when we are young.
The Centers for Disease Control and Prevention (CDC) recommends that children and teenagers in the US should be physically active for at least 1 hour a day.
Most of the daily exercise should be aerobic to help healthy development of the heart, lungs and blood vessels, but there should also be some that strengthens muscles and bones.
Aerobic activity includes, for example, brisk walking (moderate intensity) and running (high intensity). Muscle strengthening activity includes gymnastics and push-ups, and bone-strengthening activity includes jumping rope and running.
Parents concerned about their children not getting enough exercise may consider enrolling them for dance classes. However, MNT recently learned of a study from the University of California - San Diego School of Medicine that found most of kids' time in youth dance classes is inactive, suggesting parents should be careful about selecting the right dance class for their kids.