For many of us, the most pressing question about exercise is: How little can I get away with? The answer, according to a sophisticated new study of interval training, may be very, very little. In this new experiment, in fact, 60 seconds of strenuous exertion proved to be as successful at improving health and fitness as three-quarters of an hour of moderate exercise. Scientists at McMaster University ... began by recruiting 25 out-of-shape young men and measuring their current aerobic fitness. Then the researchers randomly divided the men into three groups. One group was asked to change nothing; they would be the controls. A second group began a typical endurance-workout routine. The final group was assigned to interval training, using [a] workout [that] lasted 10 minutes, with only one minute of that time being strenuous. Both groups of exercising volunteers completed three sessions each week for 12 weeks. By the end of the study ... the endurance group had [exercised] for 27 hours, while the interval group had [exercised] for six hours, with only 36 minutes of that time being strenuous. The scientists ... found that the exercisers showed virtually identical gains. In both groups, endurance had increased by nearly 20 percent, insulin resistance likewise had improved significantly, and there were significant [improvements in] certain microscopic structures in the men's muscles. Neither approach to exercise was, however, superior to the other, except that one was shorter - much, much shorter.