The science behind High Intensity Interval Training

The increasing popularity of High Intensity Interval training is due to the effectiveness of the workout in relation to the short amount of time spent on them. High Intensity Interval Training involves short sessions of high impact, strenuous movements.

There are varying approaches to this type of exercise. The first method involves completing just a single sprint (or similar exercise) for four to five minutes at 100 percent exertion, sustaining the level of exertion throughout.

Others may choose the more traditional route, and perform short sessions of exercise at an incredibly high intensity level alternated with slightly longer sessions of gentle exercise.This can be a daily habit, or one may prefer to incorporate it two to three times per week.

Although HIIT is very popular, the research behind it is relatively new. Standard, traditional HIIT has been proven to be able to improve aerobic fitness as much as 10 times more than regular endurance exercise. However, not much is known about the effectiveness of single short-burst HIIT session, or how many HIIT sessions per week would be ideal for maximum effectiveness.

Ontario’s McMaster University has begun research on HIIT training. The laboratory assembled 17 young women and men of good health into groups. Ten were required to perform exercises on two different days. Day one consisted of a standard HIIT workout (30 seconds of full intensity stationary cycling combined with four minutes of gentle recovery inbetween). Next the task was to complete one whole interval of four minutes, with each cyclist’s energy combustion being the same as when they did the standard HIIT workout. Blood and muscle samples were gathered both before and after these workouts.

On the other hand, the last seven volunteers were required to perform the uninterrupted four-minute exercise three times a week for the duration of six weeks. Once again, he researchers collected blood and muscle samples, and observed difference in the cyclist’s athletic performance by requiring them to ride at maximum effort for a specific amount of time. Comparisons revealed notable physiological deviations between between the two groups of volunteers.

Firstly, the scientists found no important differences in the response of the muscles in the cyclist’s from the first group when comparing their standard stop-n-go effort and their continuous, single session training. Both instances showed a post-workout increase in the blood levels of particular proteins that have an long term positive effect on endurance capacity.

However, the blood and muscle tissue samples taken from group two after six weeks of single interval workouts proved that what seemed like promising improvements had not come into being. The muscle tissue contained average amounts of the cells energy producing chemicals, as opposed to an elevated amount, which can be seen as an indicator of fitness. This contrasts what was previously found by the same researchers.

Although not completely clear, the study suggest that “there is something important, even essential, about the pulsative nature” of on-off HIIT training, according to Marticn Gibala, the
chairman of the department of kinesiology at McMaster University as well as senior author of the study.

Another study based at the Norwegian University of Science and Technology in Norwayasked volunteers to do 24 traditional HIIT sessions over either three or eight weeks. This meant that each subject exercised for either three times per week or nearly daily (occasionally twice on the same day).

At the end of the appointed time, the subjects who had finished three HIIT sessions per week had saw an improvement in their endurance capacity by just about 11 percent. Contrastingly, those who exercised daily exhibited no improvements and, in fact, some subject’s endurance declined. It was only once such volunteers quit the workouts altogether that their aerobic capacity started moving upwards. Twelve days post-training, their endurance reached a peak at around 6 percent higher than what it started as, which suggests that everyday high-intensity interval sessions are much too exhausting. In that situation, fatigue is more apparent than physical adaptions.

Overall, this tells one that the best method of doing HIIT is a few session every week of half minute to minute intervals and a session of recovery, repeated around four or five times. This is the way that is documented as effective and will surely help develop a difference in your endurance capacity.

If you are looking for a great HIIT workout, try the 7Min Summer HIIT workout.

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