During aging, the muscle stem cells responsible for regenerating muscle tissue become less able to multiply. Combined with changes in growth signals, this leads to a decline in skeletal muscle mass and strength. The most extreme form of this is sarcopenia, a syndrome characterized by progressive loss of skeletal muscle leading to physical disability, poor quality of life, and increased mortality. Age related muscle loss is worsened by a sedentary lifestyle, while exercise can reverse it to some extent.
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