2009 Studies & Research Blog

By now there’s already a good chance you’ve read something stating the benefits of high intensity interval training (HIIT).  This is a form of cardio training where you perform a very intense interval at an almost max out pace for somewhere between 20-60 seconds, supplemented with a minute to two minutes of active rest.  This work-rest protocol is then repeated for a total of 6-12 times, making for a very intense 20-30 session of cardio.

Some of the primary benefits you’ll get from this form of cardio are decreased time spent in the gym (which we all could use), an increased metabolic rate after the session is over, a lower chance of muscle mass loss when the sprints are implemented correctly, and a greatly enhanced physical fitness level.

Now though, it appears there’s yet another benefit you’ll be getting from doing this form of exercise, namely, an increase in total fat oxidation rates.

Researchers out of the Department of Human Health and Nutritional Sciences in Guelph, Ontario recently looked at the impact on lipid oxidation rates after two weeks of interval training in moderately active women.

They had eight women perform ten 4-minute bouts of at approximately 90% of their VO2 max with two minutes of rest between interval training for two consecutive weeks and then measurement the impacts on plasma ephinephrine, heart rate, VO2 max, and fat oxidation rates.

After the two weeks were completed, the results indicated that VO2 max increased by 13%, both plasma ephinephrine and heart rate were lower during moderate paced exercise sessions after the interval training had taken place, and there was a 36% increase in body fat oxidation rates and after moderate paced exercise sessions, net muscle glycogen utilized was reduced.

So, from this study we can conclude the high intensity interval training will help increase the body’s ability to use fat as fuel after the interval training is completed as well as when you are performing more moderate intensity exercise.

This can prove to be very beneficial since muscle glycogen is often a limiting factor impacting the fatigue you feel on any given workout session, so the less reliance you have on it, potentially the better you will be able to workout.

Reference:
Bonen, A. et al. (2007). Two weeks of high intensity aerobic interval training increases the capacity for fat oxidation during exercise in women.  J. Appl. Physiology. University of Guelph, Guelph, Ontario. Aprl;102(4):1439-47.