Muscle Fatigue / Fatigue Musculaire

Muscle Fatigue / Fatigue Musculaire


CIHR David Coulombe, Media Specialist, Canadian Institutes of Health Research.
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.
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. So we need to be listening to what our body is telling us? 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. We often hear about lactic acid. What is it exactly? 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. Would you say that stretching before and after exercising is good? 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. What advice do you have for people watching us to decrease muscle fatigue? 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. That’s interesting. Maybe for the last question: what is periodic paralysis? 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. Thank you very much Doctor Renaud. You’re welcome. Follow us on Facebook, Twitter, YouTube and Flickr. www.cihr-irsc.gc.ca

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