What is High-Intensity Interval Training (HIIT)?

If you’ve been anywhere near the fitness industry in the last 10 years you’ve probably heard of HIIT or High-Intensity Interval Training, also known as High-Intensity Interval Exercise (HIIE) or Sprint Interval training (SIT). This type of training is used among some of the worlds top athletes. It has also spurred many successful fitness movements, trainers, gyms, and weight loss success stories. Why is everyone so interested in this training style and how can it help you in your fitness journey?

How Does Interval Training Work

HIIT High-Intensity Interval Exercises are done by an individual reaching a heart rate (HR) of 85% of their VO2max for a short period of time. Then, it is followed by brief periods of low intensity activity (HR at 50% of VO2max). Each interval can last from anywhere from a few seconds to a couple of minutes done and is done a cyclical fashion repeating intervals of high and low HR in succession. After the specified numbers of cycles is completed they are separated by short durations of breaks or rest periods. 1

A good example of this would be an ice-cream stand giving away calorie-free ice-cream for the next 60 seconds, but you’re 100 yards away. You run there as fast as you can, take a second to catch your breath and notice free puppies at the other end. You have 60 seconds to get to those puppies. Well, you run there as fast as you can, take a short rest and unicorns… you get the idea. Say you had specified to do this ten times before you had a long rest period of, say, 5 minutes. After your rest period you’d continue your intervals. You’d keep going through this process for approximately 20-60 minutes. Sounds like fun, right? Well, it can be, but it’s also extremely exhausting. Your body is burning an enormous amount of calories to keep up with the energy needed to maintain such a process.

What are the Results

So, how is this type of fun (torture) good for your body? Well, training in this fashion increases muscle oxidation potential.2 This is a fancy way of saying your muscles work more effectively. It does this by training the lungs, muscles and skeletal system to utilize oxygen more efficiently. Also, your body is able to work more efficiently3 because of the way that HIIT training improves the metabolic or Krebs cycle. If you’d like to hear a quick song about how the Krebs cycle works you can watch this short video below. ⬇️

Why You Should Care

This all matters to you in the long run for a few reasons. Because of this increased efficiency in how your metabolic system works your cardiovascular system improves.  When you utilize oxygen more effectively you can build muscle better. This in turn allows you to burn more calories when you’re sitting around cuddling with your pet unicorn. Ok, that’s really only a small benefit. The real benefit is in the reduction of coronary heart disease and cardiovascular death.4  The biggest benefit of High-Intensity Interval Training is it keeps your heart young.

So, whether you’re chasing imaginary free ice cream or unicorns you might find it beneficial to add HIIT to you your routine. A few things to remember, though, is that this type of training isn’t for everyone. It can do more harm than good if you have certain underlying health conditions or if you are over-training for your particular body type. Before starting any fitness program be sure to discuss it with your healthcare provider. I’m always here to answer any questions or concerns you might have as well.



Metabolic Adaptations to Short-term High-Intensity Interval… : Exercise and Sport Sciences Reviews . Exercise & Sport Sciences Reviews. http://journals.lww.com/acsm-essr/Fulltext/2008/04000/Metabolic_Adaptations_to_Short_term_High_Intensity.3.aspx. Accessed March 21, 2017.
Burgomaster K, Heigenhauser G, Gibala M. Effect of short-term sprint interval training on human skeletal muscle carbohydrate metabolism during exercise and time-trial performance. J Appl Physiol (1985). 2006;100(6):2041-2047. [PubMed]
Perry C, Heigenhauser G, Bonen A, Spriet L. High-intensity aerobic interval training increases fat and carbohydrate metabolic capacities in human skeletal muscle. Appl Physiol Nutr Metab. 2008;33(6):1112-1123. [PubMed]
Wisløff U, Ellingsen Ø, Kemi O. High-intensity interval training to maximize cardiac benefits of exercise training? Exerc Sport Sci Rev. 2009;37(3):139-146. [PubMed]

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