One of the big characteristics of the style of exercise we program at Range of Motion is the amount of variety in what we do (learn more by reading Why we have so much exercise variety at Range of Motion).

That doesn’t just mean we have a big variety of movements and styles of exercise, but also a range of session lengths too.

Sometimes we’ll exercise for a very short amount of time (just a few minutes for the entire session, or repeated ‘intervals’ of exercise as little as five seconds). And sometimes we’ll exercise for half an hour or longer.

The shorter the session, the harder you’ll be able to work (the intensity will be higher), where-as a longer session will need to be done at a lower intensity (because you won’t be able to sustain a high work rate).

There’s good reason for this variety. Of course, it keeps your exercise fresh and interesting, but there’s a major benefit to your health to.

To understand this benefit, you have to understand the principle of ‘specificity’. Specificity basically tells us that if you want to get better at something, you have to do more of that thing. So if you want to improve your squats, the best thing to do is squats. If you’re trying to improve your push-ups, do more push-ups. The same applies to how long a training session is. If you always exercise for the same amount of time, you’ll only get the benefits of that amount of time.

The reason for this is that our body has different energy systems, different ways of fuelling your muscles to do work. Think of it like lighting a fire. You need paper to start the fire, then twigs, then sticks, then logs. All of these fuel sources are burning at the same time, but they’re burning in different amounts, and more important at different times. At the start, the paper is doing most of the work, and at the end, it’s mainly the logs.

Your body is the same, for short sessions, you’ll (mainly) use one certain energy system. And like paper, this energy system burns brightly, but doesn’t last long. As you add in progressively longer sessions your body has to go to different energy sources (just like with the fire). They don’t burn as ‘brightly’ (the exercise is at a lower intensity), but they burn for longer.

Each energy system will give you certain health benefits. Short, fast sessions will give you a certain set of benefits, moderate length sessions at a moderate intensity will give you another set of benefits, and longer, slower sessions with give you another range of benefits again.

And the benefits don’t end when your exercise session ends, the higher the intensity, the higher your metabolic rate (all the chemical reactions going on in your body) will remain for an extended period of time. To use our fire analogy, higher intensity will result in the fire continuing to ‘smoulder’ (burn fuel) for an extended period of time.

If you always exercise for the same amount of time, at the same intensity, you’ll be leaving a lot of potential benefits on the table.

So to answer the question:

We do exercise sessions lasting different amounts of time because they offer different benefits, to your health, to your body composition, and to your performance.