Brief, intense workouts offer a time-efficient alternative to longer classes according to a study just published in the American Journal of Human Biology, by Duncan Buchan, of the University of the West of Scotland. The study involved 57 school children assigned to either moderate-intensity or high intensity sessions, three times per week for seven weeks. The moderate-intensity group ran steadily for 20 minutes each session for a total of 420 minutes of exercise. The high-intensity group did a series of 20-meter wind sprints for just 3 minutes per session for a total of only 63 total minutes of exercise.
Both groups showed significant improvements in cardio-respiratory fitness, insulin resistance, body composition and blood pressure. Blood pressure improvement was actually greater in the high-intensity group. For high-intensity group participants, all these benefits were achieved with only 15% of the exercise time and a 20.5% less calorie expenditure compared to the moderate-intensity group (4410 kcal vs. 907 kcal).