If you listen to TV fitness instructors, you may hear a lot about “feeling the burn.” Of course, they never tell you exactly what “the burn” is or why it’s beneficial.
The “burn” is that tingling feeling of heaviness you get as you perform a series of repetitions of a particular strength training move. The more repetitions you endure, the more intense this feeling gets until you can no longer perform the lift.
Our cavemen ancestors would have been very familiar with this feeling. Life was hard and survival depended on being able to perform large amounts of physical work each day. Stopping as soon as you began to feel the slightest twinge of fatigue wasn’t an option.
What Causes the Burn?
The burn is thought to be caused by acidosis caused by the build up of lactic acid in the muscles when you exercise at a high intensity. Lactic acid is taken up and used as fuel by your muscles during exercise.
However, when you exercise at such a high level that the lactic acid is produced more quickly than it can be dissolved, the resulting high concentration of acid acts on the nerve receptors in your muscles to produce a localized burning sensation.
Should You Feel the Burn During Exercise?
The burn can be an unreliable indicator of strength and muscular development. You tend to feel the burn more during exercises that are isolated to a particular muscle group.
For instance, you’ll more often feel a burning sensation while doing leg extensions (which focus specifically on the quadriceps muscles) than when doing leg presses, which activate the quadriceps, hamstrings, gluteus and calf muscles.
For overall leg strength development, the leg press is a superior exercise, despite the fact that you’ll more easily feel the burn doing leg extensions.
You don’t have to exercise a specific muscle to 100% of your capacity in order to get strength benefits. In Paleolithic times, our ancestors wouldn’t have exercised to their maximum except in fight or flight situations.
While more intense exercise generally means greater strength, it’s very possible to over-fatigue your muscles by exercising to the maximum every time. Training too hard exhausts your central nervous system and lowers your capacity to withstand and benefit from intense exercise.
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