Resistance training with low-load or high-load weights produces similar muscle hypertrophy when performed to volitional failure.

Study: Muscle hypertrophy and strength gains after resistance training with different volume matched loads: a systematic review and meta-analysis.

Lifting light weights or heavy weights can make your muscles grow just as much, as long as you do enough total work and push yourself to near exhaustion.

Study: Influence of resistance training load on measures of skeletal muscle hypertrophy and improvements in maximal strength and neuromuscular task performance: A systematic review and meta-analysis

Lifting light weights or heavy weights can make your muscles grow just as much, as long as you push yourself until you can’t do another rep and do enough total work. The science shows both ways work similarly for building muscle size.

Study: Muscle Hypertrophy, Strength, and Salivary Hormone Changes Following 9 Weeks of High- or Low-Load Resistance Training

This study found that lifting light weights or heavy weights, as long as you push yourself to exhaustion, leads to about the same muscle growth. So you don’t need to lift super heavy to get big muscles—just work hard.

Study: Neither load nor systemic hormones determine resistance training-mediated hypertrophy or strength gains in resistance-trained young men

Whether you lift light weights or heavy weights, as long as you push yourself until you can’t do another rep, you’ll build about the same amount of muscle. The study showed this is true even for people who already lift regularly.