Allowing time for a rest period during your workout burns more fat than exercising for one continuous session, according to a Japanese study that could change the way we look at exercise.

The unprecedented study compared the workout sessions of seven healthy men with an average age of 25. Their respiratory gas and heart rate were monitored, and blood samples taken, while they performed the following scenarios:

• A 60-minute workout on a cycling machine, followed by a 60-minute rest period (single)
• Two 30-minute workouts on a cycling machine with a 20-minute rest in between, and a 60-minute recovery period at the end (repeated)
• A 60-minute rest period (for control purposes)

It was found that the participants had a greater amount of fat breakdown, or lipolysis, during the repeated session than the single session.

Meanwhile, the repeated trial caused a greater increase in free fatty acids and glycerol, which are released when stored fat is burned, than did the single trial. Also during the repeated session, levels of epinephrine increased and levels of insulin decreased much more than during the single session -- a combination that may have further contributed to fat breakdown.

Current recommendations by The American College of Sports Medicine to exercise for a duration of 45 to 60 minutes may therefore not be the most effective, the researchers say. Splitting up a longer exercise session with a rest period may be more beneficial, helping people to better manage and control their weight.

Journal of Applied Physiology 102(6):2158-64 June 2007

Science Blog July 18, 2007