People are habitual in nature so after a couple of months of training they are starting to see plateaus in their results.  This is usually because they have been doing the same thing for 12 weeks.  The same leg extension machine, the same ball crunches, and the same 30 minutes of Treadmill walking.  This was all fine and dandy when they first got started but now their body wants more, not the same boring stuff.  Exercise can range from gentle movements to maximal efforts.  Most every high-intensity physical activity is a state of “crisis” in the body.  Hormonally, your body basically freaks out. Then it brings out the big guns to deal with the problem. High-intensity exercise stresses the body so much that it’s forced to adapt.

HIIT is excellent for:

• losing body fat (while retaining lean body mass)
• strengthening the cardiovascular system
• developing sport-specific energy systems (e.g. training for that Olympic hockey team)
• developing “work capacity” (i.e. the ability to tolerate a high level of intensity for a longer period)
• improving fat and carbohydrate oxidation in skeletal muscle
• developing “mental toughness”
• challenging the fast twitch muscle fibers — the fibers that are great for strength and power

HIIT is extremely efficient. It lets you get a bigger training effect with less time spent. And compared to a 45-minute jog, 5 min of HIIT is a lot easier on the joints.

How to……
There are many ways to do HIIT. All you need to remember is the basic principle: Alternate short bursts of very high intensity with periods of recovery/low intensity.   One of the most famous studies of HIIT is known as the Tabata study. In this study, subjects performed rowing intervals: 20 sec of ultra-fast rowing alternated with 10 seconds of relaxed recovery rowing, for a total of 8 intervals, or 4 minutes.  At the end of the study, participants showed a 28% increase in anaerobic capacity along with a 14% increase in V02max. Pretty impressive!

Final Thoughts…..
The benefits of HIIT are exercise-specific. If you do squat jumps and running, you get better at squat jumps and running.  You can maximize your HIIT performance by using non-competing exercises. Instead of doing split squat jumps alternated with squat jumps, which use the same muscles, you could pair up bodyweight rows and squat jumps.  With really intense bouts of exercise, the body’s energy requirement can increase 2 to 20-fold!  During the first 1-2 hours after intense exercise, your body’s energy requirements remain high.
So what is high intensity? Well, during your next sprint, envision a crazy grizzly bear chasing you. That should suffice.

HIIT will not only improve body composition, it may extend your life. The Harvard Alumni Health Study, a 4-year study of more than 17,000 men, found that only vigorous – not moderate — exercise reduced the risk of death.