Scientists at the University of California, Irvine’s School of Pharmacy & Pharmaceutical Sciences have discovered how muscle stem cells “flip a switch” to rebuild damaged muscle—a finding that could help address muscle loss linked to aging, injury and widely used weight-loss medications.

The study, published this week in Nature Metabolism, shows that muscle recovery is not just about protein or exercise. It depends on timing and how muscle cells use fuel.

Researchers learned that immediately after stress, muscle stem cells temporarily slow down energy production. Instead of burning glucose for energy, they reroute it into protective repair processes to produce antioxidants that reduce inflammation. Once repairs are complete, energy production ramps back up and new muscle fibers form and strengthen.