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

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.

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

As we get older, a protein in our muscles called mTORC1 can become overactive, which slows down the body's cleanup process for damaged parts inside cells. Taking rapamycin might help turn that cleanup process back on.

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 between workouts might help your muscles clean out junk and rebuild stronger as you age — like getting the best of both rest and exercise.