Lifting lighter weights really close to failure might build muscle just as well as lifting heavy weights, but the evidence isn’t strong enough to say for sure — it might depend on how you combine weight and effort.

When lifting lighter weights, pushing until you can't do any more reps helps build more muscle than stopping early. But with heavier weights, pushing to failure doesn't give much extra muscle growth compared to stopping a bit sooner.

When lifting lighter weights, pushing until you can't lift anymore helps build bigger muscles, but this doesn't happen with heavier weights. Heavier weights always build more strength than lighter ones, no matter how hard you push.

You can build muscle just as well lifting light weights as heavy ones — as long as you push yourself until you can’t do another rep.

For beginners lifting weights, pushing muscles to complete exhaustion doesn't build more muscle than stopping just short of exhaustion, as long as the total amount of lifting is the same over 8 weeks.

Doing more sets of weightlifting seems to build muscle more reliably than how close you get to failing on each set—whether you stop short or push to exhaustion doesn’t change the muscle growth much if you’re doing the same number of sets.