High Intensity: Effective but Dangerous?

In the late 60s, Dr. Kenneth Cooper, coined the term “aerobics” to describe physical activity whereby an individual exercises for a continuous period of time, using oxygen to break down the available fuel within the body. For the next 30 years, aerobics in all its forms became increasingly popular. This included walking, running, group fitness classes, etc.

Fast forward to the last 5 years, and in a relatively short period of time, the concept of aerobics has been challenged by some variation of high-intensity conditioning, sometimes referred to as HIIT training. HIIT stands for High Intensity Interval Training and is a method of conditioning primarily the cardiorespiratory system.

Here are some of the common myths and truisms of high intensity training:

High Intensity is safe: If everybody is doing it, it must be safe, right? Not necessarily. While high intensity training is safe for most people, there are two main considerations for safety. Firstly, due to the higher levels of heart rate and breathing, if a person has a pre-existing cardiorespiratory condition, it may be aggravated before it can be improved. Secondly, high intensity sometimes includes high impact or plyometric movements. When this is the case, joint injury risk is increased. Understanding your starting fitness and health, along with the ability to modify the exercise to be safer is prudent.

Aerobics are useless: If by aerobics, you are referring to group fitness classes, two things to consider as it relates to usefulness are whether they are effective and whether there are other benefits. As to their effectiveness, group fitness classes have changed a lot over the years and many now include some kind of high intensity element to them. The other and possibly more important consideration is the side-benefit of adherence. Group fitness classes have a social element to them that may result in greater exercise adherence when compared to working out alone.

Long slow distance is unnecessary: If high intensity training is so effective in improving the measures of cardiorespiratory fitness, why bother doing long distance work at all? While high intensity work is more effective for physiological benefits, there are other elements of performance that are required, especially in events like longer distance running, cycling,  and triathlon events. For example, the only way to test your nutrition for an expected four-hour marathon would be to run for upwards of four hours. The other considerations include psychological preparedness for longer distances, and the appropriate choice of equipment including clothes and shoes, both for comfort and technical needs.

High intensity burns more fat: High intensity burns more calories when compared to the same duration of exercise at a lower intensity, and as a result burns more fat in most cases. However, when comparing short duration high intensity intervals to longer duration moderate to high intensity steady state work, the steady state work burned more calories and more fat, even after you stop exercising. The key is to work as hard as you can for as long as you can.

When comparing high intensity intervals to moderate intensity intervals and to longer low to moderate intensity steady-state work, there are many factors to consider. Most importantly is how much time you have to exercise, and how hard you will work when you are exercising. If you only have 30 minutes, a program that has you doing 60 minutes of cardio will never be used. Likewise, if you are meant to work at a 95% maximum heart rate for eight intervals, but you never exceed 75%, then you aren’t going to get the intended benefits.

If you are trying to get more results, high intensity training certainly has its place. If it is appropriate for your current fitness and health level, you can combine it with lower intensity work and strength and flexibility training along with better nutrition choices and you should be on your way to achieving your goals.