HIIT: High Intensity Interval Training
HIIT is something that I came across a few years ago and it has been worked into my routine in some form or fashion ever since. HIIT, in a nutshell, is intervals of high volume work alternated with short breaks or rest. This is a great form of exercise that burns fat by using very short but intense workouts. The sessions usually range from 4 to 20+ minutes and the protocol calls for a 2:1 ratio of rest to work periods. Example: 15 seconds sprint followed by 30 seconds rest (walk or jog), then repeat.
I don’t stick strictly to the 30sec/15sec. I mix it up a bit depending on what I am doing. I have used this workout for resistance training, running, stationary bike, elliptical, punching bag, etc.
This type of training is very popular right now and for good reason…..because it works! Circuit training, Tabata (I will do a follow-up on Tabata itself), Crossfit, and P90X are just a few examples of HIIT that is commonly seen right now.
I HIGHLY recommend reading this article. This is the one that kind of got me kick started on the whole HIIT principle. It has been widely proven that HIIT burns more calories and produces more fat loss in individuals compared to steady-state cardio but the mechanism behind this is not very well understood. Long aerobic workouts have been promoted as the best method to reduce fat, as it is popularly believed that fatty acid utilization usually occurs after at least 30 minutes of training. HIIT is somewhat counterintuitive in this regard, but has nonetheless been shown to burn fat more effectively. There may be a number of factors that contribute to this, including an increase in resting metabolic rate. HIIT also significantly lowers insulin resistance and causes skeletal muscle adaptations that result in enhanced skeletal muscle fat oxidation and improved glucose tolerance. The most novel mechanism is based around re-training your body how to process and store consumed calories. Basically it suggests that doing long, slow cardio workouts trains your body to store more fat, b/c thats what it uses to fuel those long grueling workouts. Compared to HIIT, which depletes intra-muscular glycogen stores for its energy supply. That trains your body to slowly make more room in your muscles for glycogen storage, which means than when your body is processing and filing away various calories it will now begin to store less as fat and more as glycogen!! Pretty cool stuff.
This one has some good, quick, basic interval training.
Studies have suggested that 2.5 hours of HIIT produced similar biochemical muscle changes as 10.5 hours of endurance training.
There has also been some research that indicates HIIT may increase resting metabolic rate (RMR) for as long as 24 hours following a workout due to excess post-exercise oxygen consumption (EPOC) as well as improve maximal VO2 max compared to traditional steady-state cardio.
Journal of Applied Physiology
In summary, seven sessions of HIIT over 2 wk induced marked increases in whole body and skeletal muscle capacity for fatty acid oxidation during exercise in moderately active women.
The usual excuse of “lack of time” for not doing enough exercise is blown away by new research published in The Journal of Physiology.
Recently it has been shown that two weeks of HIIT can substantially improve insulin action in young healthy men. Similarly, in young women, HIIT three times per week for 15 weeks compared to the same frequency of steady state exercise(SSE) was associated with significant reductions in total body fat, subcutaneous leg and trunk fat, and insulin resistance. HIIT may therefore represent a viable method for prevention of type-2 diabetes.