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Do Short Bouts of High Intensity Interval Training Really Work?

HIIT uses a combination of quick intervals of intense exercise and short recovery periods. The idea is to increase heart rate, burn fat and overload muscles in a short amount of time. The idea is to alternate high intensity interval training with brief active recovery periods. This is repeated for several rounds depending on the training goals. The time period for intervals is typically 30 to 60 seconds followed by one to two minutes of recovery. This is manipulated depending on fitness goal and training ability. Let’s take a look at some of the research to see what you can expect from HIIT.

Appropriate Training Intensity is the Key

There is an abundance of scientific literature demonstrating short bouts of HIIT do in fact work. This training format can have a positive affect on everything from improved aerobic capacity, to weight loss. The key, however, is the training intensity used for the “high” intensity intervals. The idea is that you should not be able to carry on a conversation during the high intensity sets. Many people may not reap all of the health benefits because they work at a lower intensity level.

High Intensity Interval Training Research

Research published in PLOS One Journal showed men who did one-minute of “all-out” exercise on bikes experienced significant improvements in cardiometabolic health measures despite exercising for significantly less time. The length of the study was 12-weeks and the sprint-interval training (SIT) group exercised for 1:00, using a 3×20 second protocol, while the moderate-intensity continuous training (MICT) group completed workouts consisting of 45-minutes of continuous cycling at ~70 percent HR max. A 2-minute warm-up and 3-minute cool-down were used for both groups, resulting in 10- and 50-minute sessions for SIT and MICT, respectively.

According to Jenna Gillen, the lead investigator of the study, “the major novel finding from the study was 12-weeks of SIT, in previously inactive men, improved multiple health markers.” Including, “insulin sensitivity, cardiorespiratory fitness, and skeletal muscle mitochondrial content to the same extent as MICT” This, despite a five-fold lower exercise volume and training time commitment. SIT involved 1-minute of intense intermittent exercise, within a time commitment of 10-minutes per session. Whereas MICT consisted of 50-minutes of continuous exercise at a moderate pace.”  

Additional Research

A second study performed at Laval University in Canada used two groups of participants. One group followed a 15-week program using HIIT while the other group performed only steady-state cardio for 20-weeks. The steady-state cardio group actually burned 15,000 calories more than the HIIT group. But, the HIIT group lost significantly more body fat.

Finally, a group of researchers from Japan’s National Institute of Fitness and Sport found a high intensity interval training program achieved bigger gains in VO2max than a program of steady cycling. Active male subjects were assigned to one of two groups, each training 5 days per week for 6 weeks. One group followed a training program involving 60-minutes of moderate intensity exercise (@70 percent VO2max), totaling 5 hours per week. The average improvement in VO2max in this group was 9 percent. Training sessions involving the other group consisted of eight all-out work bouts, each lasting 20 seconds followed by 10 seconds of rest. This group cycled for a total of only 20 minutes per week, but their VO2max still improved by 15 percent.

There is truth in saying short duration, “all-out” training can improve various health and fitness outcomes. You just need to understand that you need to “push” yourself during the short bouts of high intensity exercise. Most importantly, be mindful that there is no quick fix when it comes to improving health and fitness, if so, we would have less of an obesity epidemic on our hands in this country.

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Gillen JB, Martin BJ, MacInnis MJ, Skelly LE, Tarnopolsky MA, Gibala MJ (2016). Twelve Weeks of Sprint Interval Training Improves Indices of Cardiometabolic Health Similar to Traditional Endurance Training despite a Five-Fold Lower Exercise Volume and Time Commitment. PLoS ONE 11(4): e0154075. doi:10.1371/journal.pone.0154075

Tabata I, Irisawa K, Kouzaki M, Nishimura K, Ogita F, Miyachi (1997). Metabolic profile of high intensity intermittent exercises. Med Sci Sports Exerc. 29(3): 390-395.

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