Lifting weights until you can't do another rep, with fast upward moves and slow downward moves, helps muscles grow.

Your muscles don't grow while you're lifting weights—they grow later, while you rest, because your body uses that time to repair and build new muscle tissue after the workout stresses them.

Your muscles don't grow while you're lifting weights—they grow later, while you rest, because that's when your body repairs tiny tears and builds more muscle tissue using the energy and nutrients you've eaten.

You don’t need to push your muscles to absolute exhaustion to grow them—working them pretty hard (but not all the way to failure) might give you just as much muscle growth as going all out.

Resistance training to muscular failure induces equivalent hypertrophy in both slow-twitch (type I) and fast-twitch (type II) muscle fibers, regardless of load or repetition range.

Lifting weights until you can't do another rep doesn't help you build more muscle than stopping before you hit total exhaustion—so you don't need to push yourself to the absolute limit to get the best results.