Should you run on a treadmill ?

By Robin Clerc | lose-weight | 24 Mar 2022

Running is one of the most complete activities to be fit. It will not make you gain much muscle, but running is definitely one of the best sports for burning fat, whether in place or not. If you want to burn fat, endurance sports are the best way to go, and running is definitely at the top of the choices.

However, running in place does not improve this fact. It is almost exactly the same as running, but with 1 or 2 disadvantages. The one main difference between running in place and outside that may make you think running in place is better, but it is misleading.

You are warmer in place. You don’t have wind around you so you are heating your immediate atmosphere. Thus you sweat more.

It is right to say that just after a run in place you are lighter than after running outside for the same distance.


But the difference between the 2 workouts is you lost more water in place. You will recover this water as soon as you will drink it again. Your body will just replace it. But you did not lose more fat by running in place. Sweating is just a means for your body to evacuate warmth. Burning fat would be counterproductive because it would produce warmth instead of dissipating it.

In fact, in winter it is even the opposite.

To warm you up when you run in the cold, your body needs energy, to burn something. And it burns fat. So by running in the cold temperature you lose fat by running, and by exposing you to the cold.

But there is an aspect far more important than inside or outside for burning fat when running.

You use 2 main sources of energy when you run, fat and carbohydrates.

It is always a mix of the two.

Glycogen is limited energy storage of sugar in your blood and muscles. You have enough to run 2hours usually (unless you run on an empty stomach). It is quick to burn and can deliver energy quickly, thus it is mainly used when you run fast (when you are gasping).

Fat is also energy storage. But at the scale of a running workout, it is unlimited. You have enough fat to run hundreds if not thousands of kilometers. It is also a very efficient way to store energy. In 1kg of fat, you can store far more energy than in 1kg of sugar. However, the downside is it is slow to deliver energy. You can only run slowly if you rely only on fat.

The slower you go, the more the share of fat will be burnt. It highly depends on your level. It does not depend on your speed but more on your intensity level (your speed compared to your endurance speed)

Thus to lose fat you need to run in your endurance zone. You need to run easy. You need to be able to run for more than 30 minutes without break.

Running fast is about being competitive, to improve your cardio you should do both, running in your endurance zone, and doing high-intensity intervals to make both your muscles and your heart work at maximal intensity.

And the ideal repartition should be 80% of the time easy, 20% of the time very fast above your aerobic zone to be performant.

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Robin Clerc
Robin Clerc

Computer Science Master of Science. Site Reliability Engineer. 2h46 marathoner. Everester by bike.


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