Muscle fatigue: friend or foe?

How to minimize the negative effects of muscle fatigue

October 6, 2015

Actually, muscle fatigue is a self-defense mechanism, protecting the body from over-exertion which can trigger our muscles’ contraction mechanism.

Gradually increasing exercise, over sustained periods of time, stimulates muscles’ ability to adapt and absorb lactic acid, an important fuel source. This phenomenon explains why seasoned athletes are able to optimize their strength endurance.

Dr. Jean-Marc Renaud, a CIHR-funded researcher with the University of Ottawa’s Neuromuscular Research Centre is exploring how force can be built-up through endurance training and how his study on muscle fatigue could help find possible treatments for periodic paralysis, a condition known as hyperkalemic periodic paralysis (hyperKPP).


David Coulombe, Media Specialist, Canadian Institutes of Health Research

David Coulombe: This is David Coulombe for CIHR news. We all do biking, we exercise, we go to the gym, we do some running and we also have a problem with muscle fatigue. How can we explain this muscle fatigue? With me today, I have Doctor Jean-Marc Renaud, who is a funded researcher for the Canadian Institutes of Health Research.

Dr. Renaud, how can we explain muscle fatigue?

Dr. Jean-Marc Renaud, Canadian Institutes of Health Funded Researcher

Jean-Marc Renaud: Muscle fatigue is a protective mechanism that muscles have to prevent large depletion of energy stores. If that mechanism did not exist, then when you don’t have enough energy, there could be muscle damage, as well as a loss of muscle fibre.

David Coulombe: So we need to be listening to what our body is telling us?

Jean-Marc Renaud: Up to certain extent. I mean, the body can, to some extent, completely stop contracting and a good example is what is called “the wall” for marathoners. When they push too hard, suddenly their muscles fail to contract.

David Coulombe: We often hear about lactic acid. What is it exactly?

Jean-Marc Renaud: Lactic acid is a byproduct. When the fiber is generating energy from carbohydrates, in this case glucose, it generates lactic acid. Eventually, the mitochondria becomes active and then they use oxygen to produce more energy from glucose. However, during heavy exercise, such as playing hockey or racquetball, the mitochondria will not be activated to any large extent, so a lot of lactic acid is produced during the muscle activity. However, contrary to general belief, lactic acid and the associated decrease in pH, does not really have an impact on force generation.

David Coulombe: Would you say that stretching before and after exercising is good?

Jean-Marc Renaud: Stretching is good, especially for the tendons to make sure that they are elastic enough when you start to move. For the muscles themselves, it is not as critical.

David Coulombe: What advice do you have for people watching us to decrease muscle fatigue?

Jean-Marc Renaud: Well, being a protective mechanism, it’s very difficult to bypass muscle fatigue. However, training over a long period of time will increase your resistance to fatigue. We recently found a new phenomenon; it’s an acute effect that lasts for about three hours where a small bout of exercise with a little bit of fatigue, will actually, for three hours, increase the resistance to fatigue until the next exercise session.

David Coulombe: That’s interesting. Maybe for the last question: what is periodic paralysis?

Jean-Marc Renaud: This is a disease in which the muscle becomes completely unexcitable. Because it cannot contract at all, the patient cannot move and very often, will lie in bed for hours or even days. Our study on muscle fatigue allows us to find possible treatments for this disease. We are hopeful that by testing them with our mouse model, we can find new and better treatments.

David Coulombe: Thank you very much Doctor Renaud.

Jean-Marc Renaud: You’re welcome.

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