Or the gene that produces more fast twitch muscle fiber and has been found in all Olympic sprinters.

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Another problem with EMG prosthetics is that patients literally have to retrain their brains to make new associations between muscle movements and their outcomes a shoulder flex could become a grasp motion, for example, while a twitch of pectoral muscle in the chest may extend the artificial arm.

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Max Sick, a great early-nineteenth-century German strongman, had such complete muscle control that he could make the various groups twitch in time to music.

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