High Intensity Interval Training (HIIT):

I mentioned in "Exercising Efficiently, the Intensity Debate:” that a form of physical training known as “High Intensity Interval Training” has skyrocketed. Why is this? Well, essentially high intensity interval training (often known as HIIT) is essentially the same as interval training, but at a high intensity, funny that. For those of you who are still confused allow me to further explain through an example.

If I were to complete a high intensity interval workout it would essentially consist of a short warm up at a low pace followed by a short burst of sprinting which was then followed by a period of what is called “active recovery”. Active recovery is essentially the period in which you get your breath and energy back from the burst of energy while also running, but obviously at a lower intensity again. This would, with the omission of the warm up, be one interval, and you would then complete several intervals in a row followed by a cool down period, again obviously at a lower intensity, to complete the whole workout.

So why the popularity? Well, like most things in life some people like it and others don’t, and that’s perfectly okay. One of the most self-explanatory reasons for its popularity is simply that the workouts don’t take long. Typically your looking at no more than 20 minutes and an absolute maximum of 30 minutes. Indeed, the intervals are supposed to be very challenging and intense and therefore not able to be done for longer period of time like traditional cardio. On the down side I suppose one could say that these workouts are somewhat more gruelling that a simple stroll through the local park. Then again, some people like a challenge.

Another reason for its more recent popularity has been that current science seems to be indicating that it is most likely more effective for fat-burning than traditional long and drawn out low intensity cardio. But doesn’t this defy conventional wisdom, which states that low intensity cardio burns more fat for energy? Sort of, but not really. While low intensity activities do use more fat for fuel than higher activities (which in contrast use primarily stored carbohydrate known as glucose) there is what is now known as post-exercise fat utilisation. Basically higher intensity workouts (such as HIIT) make the body work much harder so that while your exercising fat cannot fuel the bursts of activity properly, so it uses stored carbohydrate, but after the exercise has been completed the higher intensity workouts seem to realise more fat-burning enzymes and so forth and in fact increase fat-utilisation for some period of time after the activity has ended (whereas low intensity training does nothing of a nearly comparable level).

As, http://www.sciencedaily.com/releases/2007/06/070627140103.htm, put it: “It did not matter how fit the subjects were before. After interval training, they experienced not only an increase in fat used and in aerobic capacity, but also an increase of enzyme activity in the muscle”.

Another science daily release showed that interval training in fact burned three times as much as conventional exercising in only half the time frame! So clearly there is something here in regards to HIIT. As, http://www.sciencedaily.com/releases/2007/02/070207185835.htm, stated:
“The group which did around eight seconds of sprinting on a bike, followed by 12 seconds of exercising lightly for [a total of] twenty minutes, lost three times as much fat as other women, who exercised at a continuous, regular pace for 40 minutes”. The same article continued to explain possible reasons as to why the interval sprints worked so effectively: “We think the reason that it works is because it produces a unique metabolic response,” said Professor Boutcher. “Intermittent sprinting produces high levels of chemical compounds called catecholamines, which allow more fat to be burned from under the skin and within the exercising muscles. The resulting increase in fat oxidation drives the greater weight loss.”

Amazing stuff isn’t it? But an article entitled "A Few 30 Second Sprints As Beneficial As Hour Long Jog”, is even more impressive. Other than the obvious time benefits of HIIT training it actually seems that it not only improves anaerobic fitness (i.e. ones ability to do short bursts of activity, using fast-twitch muscle fibers) but also improves aerobic fitness! This itself is truly amazing. As far as I know the opposite has not been found to be the case. As the above article states: "Short bouts of very intense exercise improved muscle health and performance comparable to several weeks of traditional endurance training”! So effectively you not only help fat-burning but also improve your cardiovascular system by simply working out less, but at a higher intensity using short bursts of power in the form of intervals!

Another sciencedaily article called “"No Time To Exercise' Is No Excuse”, illustrates “that interval-based exercise is a very time-efficient training strategy", the evidence does certainly seem to be overwhelmingly in favour of it over traditional aerobic activity.

So in short HIIT seems certain to be the most efficient form of exercise in that it has been clinically proven to burn much more fat than normal aerobic exercise and in less time, it only really takes a very short period of time in which it yields such impressive fitness results and it improves both the bodies anaerobic and anaerobic capacity in the one quick workout.

I suppose the downside is purely the intensity of it. It is certainly not suited for everyone and if you are unfit or injured or not able to push yourself it is by far best to start of with an easier regime and gather initial fitness before starting, at least that would be my advice. Then once you have a decent level of fitness you can begin HIIT training and see if it has any effect for you. Clearly factors like diet and so on will also play a large role in influecning any body composition results you may see as a result of following this exercise regime. But I’d rather work out a few times a week at a higer intensity for only a few minutes than do a gruelling hourly run each time instead… then again that being said I do seem to fair better at endurance work, but that’s largely a genetic thing. Some people just have more slow-twitch or fast-twitch muscles than others.

So what of all this fancy information about the benefits of HIIT? Well, the greatest factor for success is being able to stick to something, that motivation matters far more than what you actually do, because it determines that you will eventually reach your goals as you wish to. Also remember that there is no one ideal exercise regime, but rather that different individuals will prefer different things and be looking for different results. In spite of all the amazing research here I would still say do the activities that you love doing, as they will not be a chore to do and you will ultimately be all the healthier, both physically and psychologically for doing them. If however you are not against the idea of doing interval training then by all means give it a go, for all you know you might quite enjoy the challenge. If you don’t mind this sort of intensive training then it would make a useful addition to any training regime. So try it, give it a go and explore something new, as always if worse comes to worse and you don’t enjoy then I suggest you simply stop it and go on to find a more enjoyable way of keeping fit.