Sitting for 20 minutes between 30-minute workout sessions burns fat faster than exercising without a break, Japanese researchers are reporting.

The researchers tested the blood of seven men -- average age 25 -- during and after exercise on a stationary cycle. The men participated in three different activities: one hour of exercise and one hour of rest afterward; 30 minutes of exercise followed by a 20-minute rest and then a second 30-minute workout followed by an hour of rest; and an hour of rest without exercise. The men sat in a chair during the rest period.

The workout that was broken into two half-hour segments resulted in more fat breakdown than the other two activities, the researchers report in the June issue of the Journal of Applied Physiology. The second half-hour workout also showed a greater boost of epinephrine and a rapid decrease in insulin as a result of lower plasma glucose. The researchers theorized that these chemical events contribute to the fat breakdown.

The researchers noted that the American College of Sports Medicine recommends moderate exercise for 45 to 60 minutes to burn fat. However, the researchers argue that their results show the benefit of a rest period during the workout.

"Many people believe prolonged exercise will be optimal in order to reduce body fat, but our study has shown that repetitions of shorter exercise may cause enhancements of fat mobilization and utilization during and after the exercise. These findings will be informative about the design of [future] exercise regimens," lead researcher Kazushige Goto, of the University of Tokyo, said in a prepared statement. "Most people are reluctant to perform a single bout of prolonged exercise. The repeated exercise with shorter bouts of exercise will be a great help [in keeping up with fitness]."


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