If you're a healthy young adult lifting weights, lifting heavier weights (fewer reps) helps you get stronger faster than lifting light weights (more reps), but lifting medium weights works almost just as well as heavy weights — the difference isn't big enough to say for sure.

Lifting heavier weights (fewer reps) leads to bigger strength gains than lifting lighter weights (more reps), even if both are done until exhaustion.

Lifting heavier weights might help you get stronger a bit more than lifting lighter weights, but the difference is so small that we can’t be sure it’s real — it could just be luck.

Lifting heavier weights for nine weeks made young men stronger in a max lift test than lifting lighter weights, even when both groups worked until they couldn't do another rep.

Lifting heavy weights might help you build slightly more muscle than lifting light weights if you're new to training, but the difference isn't big enough to say for sure it's real.

For exercises that move just one joint—like bicep curls—lifting heavier weights leads to better strength gains than lifting lighter weights, even if both are done until exhaustion.