We all know exercise is good for us. It builds muscle, strengthens bones, lowers blood pressure, and boosts mood. By deciphering how movement benefits the body, researchers hope to develop medicines that can offer some of the same perks—without the workout. The idea isn’t to replace exercise but to bring its upsides to people who struggle with frailty, disability, or chronic illness.

The sticking points

It will take a lot of experimentation to untangle the myriad pathways by which exercise promotes health. But IDing the cascade of hormones, enzymes, and other molecules related to physical activity is just the first step. Scientists need to figure out how to turn that knowledge into safe and effective drugs. That’s a tall order: More than 90% of treatments that enter human studies fail.

There are regulatory hurdles too.…