Giving older mice a drug called rapamycin helps keep their muscles strong and working well as they age, especially in some muscles but not others.

Rapamycin might help older animals keep their muscle and stay lean by tweaking a key cell signal involved in aging.

Turning on a certain signal in mouse muscles makes them age faster, causing nerve and muscle problems like those seen in old age — but this can be reversed with a drug called rapamycin.

Taking rapamycin with exercise might help improve muscle strength in older people by affecting a specific cell pathway in the body.

Older mice with overactive mTORC1 had higher levels of certain muscle-related amino acid processes after taking rapamycin, which might help muscles handle stress and stay healthy.

In older mice with overactive muscle metabolism, giving them a drug called rapamycin changes the types of fats in their muscles — some go up, some go down — which might mean the drug helps reset how aging muscles handle fat.