A common workout myth is that lactic acid build up makes muscles fatigue. We now know that lactic acid has little to do with muscular fatigue. We are not sure of the cause, although calcium depletion might be indicated. Please refer to this article in the New York Times. Included are references to recent studies.
The following is an excerpt:
“For decades, muscle fatigue had been largely ignored or misunderstood. Leading physiology textbooks did not even try to offer a mechanism, said Dr. Andrew Marks, principal investigator of the new study. A popular theory, that muscles become tired because they release lactic acid, was discredited not long ago.
In a report published Monday in an early online edition of Proceedings of the National Academy of Sciences, Dr. Marks says the problem is calcium flow inside muscle cells. Ordinarily, ebbs and flows of calcium in cells control muscle contractions. But when muscles grow tired, the investigators report, tiny channels in them start leaking calcium, and that weakens contractions. At the same time, the leaked calcium stimulates an enzyme that eats into muscle fibers, contributing to the muscle exhaustion.”
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