High Intensity Interval Training (HIIT)

Article by William Hammer

High Intensity Interval Training (HIIT) is not new, but seeing it promoted in a home workout program is new. Chalene Johnson, creator of TurboFire, said that one of the reasons she created the new program is because she wanted a home workout program that took advantage of the benefits of HIIT. One of those benefits is that according to the TurboFire promotional information, this type of training can deliver 9 times the fat burning results of steady state aerobics workouts. This is quite a claim; could it possibly be true? To figure it all out, we’ll look at HIIT and some of the many scientific studies that have been conducted to test the efficacy of this training system. Our goal is to determine if the seemingly sensational claims about fat loss that are being made by the TurboFire promoters could be true.

What Exactly is High Intensity Interval Training (HIIT)?

High Intensity Interval Training or Sprint Interval Training has been around as a technique with a fancy name since the 1930s and in general long before that. Many credit German Coach, Dr. Woldemar Gerschler with popularizing the interval training method for Olympic runners. Some call him the “father” of interval workouts. As one might guess, Gerschler used Interval Training to improve the speed of athletes.

The method of Interval Training Gerschler developed is different in the methods most often used today. Gerschler and cardiologist Dr. Herbert Reindel worked together with thousands of runners to find the precise training system that would maximize the efficiency of the heart. The method that they perfected was based on heart rate and not on timed intervals. Gerschler would have his runners run short sprints of 100 meters or more to achieve a heart rate of 180 beats per minute (bpm). Then the heart rate was monitored and as soon as it dropped back down to 120, the next sprint was run. If the heart rate stayed elevated above 120 for more than 90 seconds, the sprint was reduced in intensity or length. The athletes that trained under Gerschler utilizing his Interval training system were remarkably successful. His runners set world records in 1939, 1952 and 1955.

High Intensity Interval Training Today

Modern practitioners of HIIT follow the principals that Gerschler and Reindel developed but have refined them to include some steady state aerobic exercise during the recovery period. This has been shown to increase the effectiveness of interval training. Additionally most HIIT is done my timing the intervals instead of using heart rate measurement as Gerschler did.

What used to be called wind sprints is probably the simplest and oldest form of High Intensity Interval Training. So if you played any type of field sport as a youngster, your coach probably had you doing High Intensity Interval Training, although they probably didn’t use that term or the cool acronym, HIIT.

For a long time, the ideal proportion of recovery to intense workouts was considered to be 2 to 1, meaning a short burst of exercise for one minute separated by a recovery period of two minutes. But many programs and trainers vary from this formula greatly. For example, one well-known study used a regimen with a 1.25 to 1 ratio and another had a ratio of 8 to 1. Although the ratio of recovery to intense workout sessions vary greatly, both of the studies that used these ratios measured positive results from the High Intensity Interval Training workouts. The common rule of thumb is that HIIT workouts should be 15 to 20 minutes and should include a warm-up and cool-down periods before and after the intense sessions.

High Intensity Interval Training and Fat Loss

The seemingly unbelievable claim that Interval Training will result in “9 times” the fat burning that is so often sited comes from a 1994 study by Angelo Tremblay, Jean-Aime Simoneeu and Claude Bouchard, which states that they measured a “ninefold” increase in fat loss in the interval training group (HIIT) versus the group doing just steady state training. Although, some have questioned the use of this number as “out of context” other studies have drawn conclusions, which have shown a much higher efficiency with High Intensity Interval Training as well.

In order to avoid the charge of taking anything out of context, here is the relevant quote from the Tremblay study in it’s entirety: “When corrected for the energy cost of training, the decrease in the sum of six subcutaneous adiposity induced by the HIIT program was ninefold greater than by the ET program.” Subcutaneous adiposity is the term that the medical community and researches use to describe what the rest of us call fat. “ET” in the study refers to “endurance training” or steady-state training.

It is important to note that in this study that the researchers corrected for energy costs – in other words they were comparing the effectiveness of the fat loss of the exercise and not the total amount of fat loss. The actual difference in fat loss was 3 times. Both groups of participants in this study saw a reduction of fat, but neither group lost much weight. Others have noted that in this particular study the HIIT group had a higher body fat composition on average than the control group and have suggested that this contributed to the increase fat loss results in the High Intensity Interval Training group.

As far as we could uncover there were no other studies that measured fat loss and High Intensity Interval Training, but there are plenty of other studies that measure the effectiveness of HIIT. A study released in March of 2010 by scientists at Canada’s McMaster University, demonstrated that just 2.5 hours of High Intensity Interval Training or sprint-interval training spread out over a week produced similar biochemical muscle changes as 10.5 hours of endurance training and similar endurance performance benefits. Therefore, according to this study High Intensity Interval Training is more than 4 times as effective as steady state training. This study was not measuring fat loss but factors that determine “volitional exercise performance” or what us layman might call fitness.

Another study by Jeffery King for a thesis at east Tennessee State University, found that HIIT increases the resting metabolic rate for the following 24 hours.

This is not a study, but the following quote from a New York Times articles is a strong endorsement for High Intensity Interval Training: “Doing bursts of hard exercise not only improves cardiovascular fitness but also the body’s ability to burn fat, even during low or moderate-intensity workouts, according to a study published this month, in the Journal of Applied Physiology.” Interval training also stimulates change in mitochondria, where fuel is converted to energy, causing them to burn fat first.”

So it seems that the scientific and fitness communities are in agreement: High Intensity Interval Training is an unusually effective way to burn fat and get in shape in less time than doing a standard aerobic workout. One study has determined that HIIT is 9 times as effective at burning fat than a standard aerobic workout. And although some have questioned the methodology of this study, since TurboFire promoters are quoting an academic study, they are on solid ground making the claim that it burns more fat than steady-state aerobic workouts.

However, we should note that in order to do High Intensity Interval Training properly requires that you are able to exercise at maximum effort repeatedly. This requires that you have been doing some exercise. Some guidelines suggest that you must be able to exercise at least 30 minutes at 70% of your estimated maximum heart rate without exhausting yourself in order to safely train using HIIT. Anyone who is below this level of fitness would need to exercise regularly at a less intense level to build up to this level to be able to utilize HIIT. And as always, consult your primary care doctor before engaging in any strenuous physical activity if there is any question about whether you can handle High Intensity Interval Training.

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