Intense Exercise
Martin Gibala had a group of college students, who were healthy but not athletes, ride a stationary bike at a sustainable pace for between 90 and 120 minutes. Another set of students grunted through a series of short, strenuous intervals: 20 to 30 seconds of cycling at the highest intensity the riders could stand. After resting for 4 minutes, the students pedaled hard again for another 20 to 30 seconds, repeating the cycle 4-6 times (depending on how much each person could stand), for a total of 2-3 minutes of intense exercise per training session.
Each of the groups exercised 3 times a week. After 2 weeks, both groups showed almost identical increases in their endurance (as measured in a stationary bicycle time trial), even though one group had exercised for 6-9 minutes per week, and the other about 5 hours. Additionally, molecular changes that signal increased fitness (such as increased volume of muscular mitochondria) were evident equally in both groups. The short, intense workouts aided in weight loss, too; the rate of energy expenditure remained higher longer into recovery after brief, high-intensity exercise than after longer, easier workouts. (Other researchers have found that intense, brief sessions of exercise improve cardiac health, even among people with heart disease.)
“Can You Get Fit in Six Minutes a Week?,” by Gretchen Reynolds