If you push your muscles as hard as you can until you can't do any more reps, that's what really makes them grow bigger. It doesn't matter how many reps you do, as long as you're giving your absolute best effort.

When you lift weights until you can't anymore, you build about the same muscle size no matter how many reps you do, but doing more reps makes you stronger than doing fewer reps.

Going all the way to exhaustion on every set probably doesn't build more muscle than stopping a few reps short — both seem to work about the same.

When people who are already fit push themselves as hard as they can during weight training, it doesn't matter if they lift heavy weights for a few reps or lighter weights for many reps—both ways build muscle about the same.

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 lift weights until you can’t do another rep, it doesn’t matter if you’re using light, medium, or heavy weights—you’ll still grow your muscles about the same, as long as you push yourself hard and do enough total work.