When untrained men lift weights until they can't do any more reps, they get more tired over time compared to stopping earlier, meaning their muscles wear out faster.

For beginners, stopping resistance exercises just before your muscles give out works just as well as pushing to complete failure for building muscle strength and size, whether you're lifting heavy or light weights.

If you lift weights until you literally can't do another rep, you'll feel more tired right after than if you stop a couple reps before failure — even if you're someone who regularly lifts weights.

Going all the way to muscle failure during weight training makes you way more tired—both mentally and physically—but doesn’t help you build more muscle than stopping just short, so it might not be worth the extra effort.

Lifting weights until you're tired, whether with light or heavy weights, makes your muscles bigger and stronger in the same way for beginners.

If you train with weights that change resistance throughout the movement (like using bands or machines that adjust), you can do more reps and lift more total weight before getting tired than if you use the same weight the whole time — and after 20 weeks, this difference is pretty big.