I'm Dr Shannon Ritchie. I'm a doctor of physical therapy fitness trainer and

founder of Hello Fitness. In the Dr Shannon show you'll learn applicable tools

to improve your health based on science. Welcome to the show.

Hi everyone, today we are talking about that burning sensation that you feel during exercise and I'm always saying how the burn in itself isn't the stimulus that causes muscle growth.

So if it's not causing muscle growth, what is the benefit of

exercises that burn? So many of us are familiar with that burning cessation that

happens during exercise and this burn is called metabolic stress.

It happens when a buildup of metabolites like lactate and hydrogen

cause an uncomfortable sensation within the muscle tissue.

This happens when an exercise relies on anaerobic

glycolysis for energy, usually in an exercise that is a little bit longer. It could last

anywhere from 15 to 120 seconds, but generally you start to feel the burn when an exercise

exceeds about 45 seconds long.

This burning sensation is associated with discomfort and therefore fatigue, which is important to note and something that we'll discuss here in just a moment.

So this metabolite buildup, does it stimulate growth?

Research one thought, once thought that metabolic stress builds muscle,

but it has since been debunked.

More current research shows that metabolic stress

is associated with muscle growth growth but does not cause muscle

growth. It's not the stimulus that triggers muscle growth. What causes muscle growth is

mechanical tension. Mechanical tension is force spread over a muscle.

So as you're lifting weights, the force to the muscle causes that muscle to fatigue.

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