Divergent Strength Gains but Similar Hypertrophy After Low-Load and High-Load Resistance Exercise Training in Trained Individuals: Many Roads Lead to Rome.

When people lift weights until they can no longer complete another repetition, the amount of muscle growth is similar whether they use light, moderate, or heavy weights.

If you lift weights until you can’t do another rep, your muscles will grow about the same no matter how heavy the weights are—but you’ll get stronger faster if you lift heavier weights.

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.

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.

When muscles are trained to complete fatigue, both slow-twitch and fast-twitch muscle fibers grow by the same amount, no matter how heavy the weight or how many repetitions are performed.

When resistance training is performed to muscle failure, low-load with many repetitions produces the same amount of muscle fiber growth as high-load with few repetitions.