If we block a certain protein in the body for a few weeks, it might calm down long-term inflammation in older tissues and help them work better again — possibly by waking up old stem cells and improving the immune system.

The study gave an mTOR-blocking drug weekly for 13 weeks to older adults exercising at home, but it didn’t help their physical function—and might have made gains worse—so it doesn’t support the idea that stopping the drug leads to rejuvenation.