Older male mice have bigger changes in muscle chemicals after taking rapamycin than older female mice, suggesting their bodies respond differently to this drug as they age.

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.

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.

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.

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

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.