If you lift weights until you can’t do another rep—whether you use heavy weights or light ones—you’ll end up with about the same muscle growth after nine weeks, as long as you’re putting in the same effort and number of reps.

Whether you lift light weights with lots of reps or heavy weights with few reps—so long as you push until you can’t do another rep—you’ll build muscle about the same amount.

If you're already someone who lifts weights, doing light weights twice a week until you can't do more reps can make your muscles bigger and stronger in just 8 weeks.

If you're a young man who already lifts weights, doing workouts with either light weights (lots of reps) or heavy weights (fewer reps)—as long as you push yourself until you can't do another rep—will make your muscles grow just as much either way.

You can get stronger and bigger muscles by lifting light weights until you're exhausted — even if you never lift heavy, which challenges the old idea that heavy weights are required.

Whether you lift heavy weights for fewer reps or light weights for more reps—as long as you push until you can’t do another rep—your muscles grow about the same amount.