While most muscles in mammals contain a mixture of slow- and fast-twitch fiber types, some muscle beds are enriched for one type or the other, Spiegelman said.

Spiegelman说，大部分哺乳动物的肌肉包含两种类型的肌纤维，但有些肌肉是偏重于富含其中的一种。

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Kenyans and East Africans in general tend to be short and slender with large natural lung capacity and a preponderance of slow twitch muscles.

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