High Intensity Interval Training, otherwise known as HIIT, is a workout craze becoming more and more popular due to its promise to deliver health benefits and weight loss similar or better to those achieved with steady state exercise, but in a much shorter time frame.
What is HIIT?
HIIT workouts are comprised of short bursts of very high intensity sprints for a time frame ranging from 10 seconds to up to several minutes with a recovery period of one to five minutes at a low intensity or in a resting state.
This is repeated over a certain time frame, which could range from as little as four minutes to up to twenty in trained individuals. This type of workout is claimed to burn as many calories, increase aerobic fitness and give other health benefits similar to or even better than those achieved when doing exercise at a slower pace for a longer time frame.
What does the evidence say?
Although it a fairly new concept in the workout scene, research into the benefits of HIIT has been underway for much longer than this and many studies have been done investigating the effects of such an exercise regime. HIIT has been associated with cardiovascular and metabolic benefit in both at risk and healthy people and has been found to have a higher compliance level than more typical exercise regimes.
Regular HIIT has also been associated with increased levels of both aerobic and anaerobic fitness and recent research suggests that it may be more effective than other forms of exercise in reducing subcutaneous and abdominal fat, although the mechanism for this is not clear yet.
Insulin resistance and improved glucose tolerance have also been associated with a HIIT regime, which may reduce risk of type 2 diabetes.
What are the advantages gained from HIIT?
The research suggests that HIIT results in health benefits at least as good as steady state exercise, if not better and it can be done in a much shorter time frame. For those who live busy lifestyles and have little time to work out, HIIT is an excellent option to get the benefits of exercise in short time.
For those who have hit a weight loss plateau, starting a HIIT regime may help to kick start weight loss again.
What are the disadvantages?
Although HITT may seem largely advantageous, there are some drawbacks to this type of exercise program. For obese patients and those who are at high risk of heart disease, such an intense form of activity may not be advisable and certainly should not be carried out without medical supervision.
Likewise for those who are not used to exercise and have a very low level of fitness, this type of program may not be suitable, at least in the first instance.
It should also be noted that to get the benefits from HIIT, it needs to be done properly. You really need to be working hard during the sprint sessions, ideally at a high heart rate and this type of training is best suited to being done under the instruction of a trainer, especially for those who have limited exercise experience.
It should also be noted that this method of training is intensive and may not have the stress relief benefits or social factors that other more relaxed forms of exercise have.
Many of the studies resulting in good levels of fat loss using HIIT have used a very intensive program involving 30 second sprints but more research needs to be done into optimizing the regime for the general public.
Is HIIT the best way to lose fat?
Whilst some past research comparing HIIT with steady state exercise has shown little difference in fat loss between the two groups, it should be noted that the time needed to achieve the same fat loss in the HIIT group was half that required from the steady state group.
Thus it seems that for the time needed, HIIT is indeed a more efficient way to burn fat.
More recent studies have shown that HIIT training decreases levels of abdominal and subcutaneous fat significantly when compared to steady state exercise, although it is unclear why this is the case. I
It is possible that skeletal muscle changes may result in more oxidation or burning of fat than improved glucose tolerance may contribute. Some animal studies have also shown that HIIT may act to suppress the appetite, which may be another mechanism that results in less intake of food and therefore loss of fat.
Studies have shown a lot of variation in fat loss with HIIT, and it should be remembered that other factors such as diet and every day activity levels may also contribute to fat loss and need to be considered in conjunction to any weight loss exercise regime.
References used in this article