When older women lift weights for 8 weeks, their muscles don’t get much bigger, but they do get stronger and walk faster—so it seems like something other than bigger muscles is helping them move better.

After doing strength training for 8 weeks, older women got stronger and their muscles worked better—but their muscles didn’t get bigger. This suggests their brains and bodies got better at using the muscles they already had, not at making new muscle.

After 12 weeks of lifting weights, both strong and weak older women gained about the same amount of muscle—starting strength didn’t affect how much muscle they built.

When older women do strength training for 8 weeks, they tend to walk faster if their leg muscles get stronger or work better—but not if they just gain muscle mass or lose fat.

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.

Older women who started out weaker in their legs got stronger in their legs more than the stronger ones after doing leg exercises for 12 weeks, but everyone gained about the same amount of muscle and upper-body strength.