Muscle contraction is the tightening, shortening, or lengthening of muscles when you do some activity. It can happen when you hold or pick up something, or when you stretch or exercise with weights.
"Hearst Magazines and Yahoo may earn commission or revenue on some items through the links below." IF YOU'RE LIKE most guys in the gym, when you’re doing a big lift—whether it’s a max bench, a PR ...
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