High Intensity Interval Training (HIIT) is a form of training that involves periods of high intensity exercise followed by periods of recovery. Some of you may have heard of Tabata, and THAT is a form of HIIT. HIIT can be applied to pretty much any workout. I’ve seen it used in cycling and dance classes, athletic training, weight training, and pretty much any other form of training you can think of. So, what are the benefits of HIIT and why has it become so darn popular over the past decade?
An article published by Canadian Science Publishing showed increases in skeletal muscle adaptations that allowed for fat and carbohydrate oxidation from 6 weeks of HIIT 3 times per week.
Journal of Strength and Conditioning Research published a study that showed 5 weeks of HIIT on 14 y/o soccer players showed increased VO2 max and faster 1,000 meter times vs. other forms of training.
Another study done by the Natural Sciences and Engineering Research Council of Canada compared a 20-week endurance program to a 15-week HIIT program. The endurance program required a greater energy cost than HIIT yet the fat reduction from HIIT was 9 fold higher than that of the endurance program. Enzymes that breakdown sugar in the muscles for energy also showed to increase in activity after the HIIT program and actually DECREASED after the endurance program.
So, there are a few studies that show HIIT as being a better alternative to traditional endurance training, but I was really curious as to what all of that data meant and WHY HIIT showed greater improvements, so I started digging into the different adaptations seen from HIIT as opposed to say longer endurance based exercises. Here’s what I was able to find.
A study done by the Norwegian University of Science and Technology, Hokksund Medical Rehab Centre, St. Olav’s University Hospital showed that HIIT increased stroke volume of the heart by 10% more than the endurance training. Stroke volume is how much blood the heart can pump per contraction of the heart. Stroke volume directly influences VO2max, which is the main indicator of cardiovascular fitness. VO2max is the max volume of oxygen that your body can absorb and utilize for energy production.
SO, what all of this essentially means is that because HIIT forces your heart to beat faster and causes you to breathe harder, your body must adapt to those demands more urgently than of more moderate forms of training. A study done by Martin Gibala of McMaster University showed an increase in mitochondrial density in the muscles with HIIT. The only thing any of us learned in biology class was that the mitochondria is the powerhouse of the cell. Mitochondrial density is defined as the number of mitochondria that use oxygen to form ATP, which is energy. So because your body becomes better at utilizing oxygen, your muscles are able to adapt to higher demands such as the high intensity intervals. This explains a little more descriptively why the studies at the beginning were showing greater muscle adaptations.
If you are mildly pessimistic like me, someone who never believes there is not SOME negative to everything, then you are wondering what the negative repercussions of HIIT are. Well I tried to find some studies of some negative effects of HIIT and just could not find any. Even for people with heart conditions it seemed to help control symptoms, however this is just a hypothesis and scientists are still researching this, so continue with caution. That being said, HIIT studies are still being conducted today, and none of this information is final. There may very well be some sort of downside to HIIT, though currently, that does not seem very likely.
For me, I personally love HIIT. I like to sweat, and this style of training takes half the training time as more traditional styles of training, with more than twice the benefits. The most important point that I see is exercise adherence. Most people just simply enjoy HIIT better than other forms of exercise. I mean, just look at CrossFit. There is a heavy emphasis on interval training there and it has one of the largest followings as far as exercise groups are concerned. Not only does it seem to be more enjoyable, but there is a much smaller time commitment. Sure, you have to work really hard during this shorter time period, but it still allows you to get in and get out, which combats the, “I don’t have time for exercise” excuse that many of you try to use. This could literally be done in a mere 20 minutes. You can find 20 minutes in your day, I guarantee it. Just prioritize it and you will get it done.
My only concern with HIIT is that people might try to use exercises that they are not prepared for during their training. HIIT training is high intensity, and if you start doing exercises that you have not mastered the form of, you could very well injure yourself, and that is obviously not good for exercise adherence. My only real warning if you want to give HIIT a try is also one of my big training philosophies, “Form over everything.” Build a base for your training before you start loading yourself with either weight or high intensities. I’ve seen dead lifts used in high intensity training and holy crap if you do that wrong you will end your lifting career. Just be confident with the movements. After you do that, go wild. HIIT training is quick, fun, and highly effective and if you’ve never given it a try, you should. The results might surprise you.
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Now get out there and get after it! This is Life&Fitness with D. Banks, signing off now, see you later.