High Intensity Interval Training (HIIT)

What is HIIT?
High Intensity Interval Training is a form of interval training that incorporates alternating periods of high intensity exercise immediately followed by low intensity exercise. This is continued in a repetitive fashion for several minutes. The periods can range from several seconds up to several minutes and range from a 2:1 time ratio(Tabatha Method) to 2:3 time ratio for High Intensity:Low Intensity.

HIIT can use any form of cardio exercise/equipment that allows you to quickly change the intensity of the workout, including running, cycling and rowing.

Although the session only lasts several minutes, the outcomes have been shown to be quite significant in trained and untrained athletes.

How does it work?

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HIIT places a high demand on the body for oxygen during the High Intensity intervals and ultimately results in an anaebolic (Without oxygen) exercise routine due to the level of intensity and duration of the workout. Because of the deprivation of oxygen, the body requires an extended period to recover from the exercise. By doing this, there is an increase in the Resting Metabolic Rate (RMR) for up to 24 hours following the training, this improves energy consumption and fat loss. The faster your metabolism, the easier it is for your body to burn fat.

"As little as six sessions of HIT over 2 week or a total of approximately 15 min of very intense exercise(~600kJ), can increase skeletal muscle oxidative capacity and endurance performance and alter metabolic control during aerobic-based exercise." (Gibala 2008)

Skeletal muscle oxidative capacity - The efficiency of the muscle to break down fat and carbohydrates to create energy (ATP). ATP is used to power the movement of the muscle fibers during contraction and relaxation.

For elite athletes who struggle to improve time and fitness, HIIT has been shown to be the most effective form of training.


Gibala MJ, McGee SL 2008 Metabolic Adaptations of Shirt-term High-intensity interval training: A little pain for a little gain? Exercise & Sports Science Reviews 36(2):58
Laursen PB, Jenkins DG The Scientific Basis for High Intensity Interval Training. Sports Medicine 32(1):53
http://en.wikipedia.org/wiki/High-intensity_interval_training
http://en.wikipedia.org/wiki/Muscle

For more information:
http://www.bodybuilding.com/fun/bbinfo.php?page=HIIT