After older guys rest their legs for a bit, getting back to strength training with extra protein might help their leg muscles grow back stronger than before they took the break.

If older guys between 60 and 80 don’t use their legs for two weeks, they lose leg muscle and strength—but just two weeks of exercise plus drinking protein twice a day can bring it all back.

Older women around 69 years old who drink a whey protein shake every day and lift weights three times a week for three months may gain more muscle, lose belly fat, and improve their overall metabolic health more than those who just do the workouts without the protein.

After drinking whey protein shakes every day for a week, older women’s muscles kept building up new protein even on days they didn’t exercise—collagen protein didn’t do this at all.

If older guys who are already active do full-body strength training three times a week for three months, they’ll get stronger legs and bigger leg muscles—even without adding extra protein to their diet.

Middle-aged men doing strength training don't change their protein intake whether they take collagen, whey, or a placebo.