If I am working high intensity interval training (HIIT) into my home workouts then I do shuttle runs, sprints, kettlebell swings, stair running, or a bodyweight cardio workout.
Here is the snapshot of what these workout routines looks like:
- 5 min warm up gradually increasing intensity
- 15-20 minutes of intervals: 8 seconds at intensity level 8/10 followed by 12 seconds at intensity level 3/10
- 3-5 minute cool down at an easy pace
Why such short intervals when most of the trainers out there today are using much longer intervals of 30, 45, or even 60 seconds? Let alone the trainers that still think long, slow cardio sessions of steady pace activity for 30-45 minutes are the best way to lose fat and increase fitness.
The reason for these shorter duration higher intensity intervals is……..well, we really don’t know exactly why. But we can speculate…..more on that in a minute.
But through trial and error, actually testing different high intensity interval and recovery interval times, researchers have found the optimal levels for oxygen uptake and energy expenditure.
This study, published in 2004 entitled “Oxygen uptake response to high intensity intermittent cycle exercise”, determines that the 8 seconds on, 12 seconds off method was optimal.
It is speculated by Professor Boutcher, one of the investigators of the study, that this interval duration is optimal for stimulating the release of substances in your body called catecholamines.
According to Boutcher, “Intermittent sprinting produces high levels of chemical compounds called catecholamines, which allow more fat to be burned from under the skin and within the exercising muscles. The resulting increase in fat oxidation drives the greater weight loss.”
I believe that catecholamines are not the only substance at work here, but perhaps just one aspect of a “chemical cocktail” of sorts. I believe that growth hormone and lactic acid also play a part in fat loss as well, just to name a few.
And one thing to note, this research study was conducted on women, notorious for extra fat in the hips, thighs and belly regions. This method of exercise actually “spot reduced” these areas with minimal or no changes to the diet. Almost unbelievable!
So, if you are incorporating high intensity interval training into your workout routines now, then try changing the time of the intervals to 8 seconds on and 12 seconds recovery and work up to 20 minutes.
If you are not currently doing high intensity intervals and would like to start, please contact your physician and then start slowly. You can start by using the 8 sec/12 sec method but do not increase your intensity level past a perceived exertion level of 6/10.
Exercise smart and start using HIIT today!
Susan Campbell, MS, CSCS
Author, Ultimate Home Workouts