High-Intensity Interval Training (HIT) is back in the news again.  A small study published in the March 2010 issue of the Journal of Physiology showed that in men, short bursts of intense exercise works just as well for increasing muscle fitness as longer, lower intensity exercise.  In this case, fitness is defined as the ability to do work due to increased number of mitochondria (the energy centers of all cells; the more mitochondria you have, the more work you can do before your muscles get tired) and increased vascularization.  The same journal published an article back in 2006 reporting the same thing; however, this time the intensity of the work performed by the participants was less.  The 2006 study looked at “four and six 30-second bursts of “all out” cycling separated by 4 minutes of recovery” on a special laboratory bicycle, while the 2010 study had the participants performing “10 one-minute sprints on a standard stationary bike with about one minute of rest in between” with each sprint performed at approximately 95% of maximum heart rate.  Still uncomfortable to be sure, but only about half of the heart rate one can achieve going “all out”.

What does that mean for you?  That means that lack of time is no longer a reason to not work out.  I already gave you some basic interval training workouts in this article.  Here are a few more.

Beginner: Start with 6 intervals of 30 second sprints followed by 90 seconds rest periods.  Gradually work up to 12 intervals.  Start with a 3 minute warm up and end with at least a 3 minute cool down.

Intermediate:  Start with 6 intervals of 30 second sprints followed by 60 second rest periods.  Start with a 3 minute warm up and end with at least a 3 minute cool down.  Same graph as above except only two lavender bars between sprints.

Advanced:   Start with 6 intervals of 30 second sprints followed by 30 second rest periods.  Gradually work up to 12 intervals.  Start with a 3 minute warm up and end with at least a 3 minute cool down.  Same graph as above except with one lavender bar between sprints.

Sprints should be at about 90% of your maximum heart rate.  Rest periods should drop to 50%.  Alternatively, you could look at it as 90% of maximum effort for sprints and 50% of maximum effort for rest periods.  Do these no more than every other day.

More info on this topic: http://www.sciencedaily.com/releases/2010/03/100311123639.htm
Original article:  http://jp.physoc.org/content/588/6/1011