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If that promotes the development of fast-twitch muscle fibres in growing foetuses, that could add to the Jamaican edge. The truth is, we donât have enough information to draw firm conclusions about the Jamaican dominance of sprinting. But there is good reason to dig deeper â and it has nothing to do with athletics. We now have evidence that extreme stress, heat, cold, malnutrition and pollution (including tobacco smoke) trigger changes in the way genes are activated or silenced.
A single action potential in a motor neuron is sufficient to produce an action potential in a skeletal-muscle fiber. Table 11-2 summarizes the events leading to the contraction of a skeletal-muscle fiber. Muscle fibers form ATP by the transfer of phosphate from creatine phosphate to ADP, by oxidative phosphorylation of ADP in mitochondria, and by substrate-level phosphorylation of ADP in the glycolytic pathway. 2  At the beginning of exercise, muscle glycogen is the major fuel consumed.