Muscles can't grow bigger unless the tendons and joints around them are strong enough to hold the extra weight.

Your muscles grow bigger not because of just one thing like lifting heavy weights or doing lots of reps, but because of how all the workout factors—like how hard you push, how often you train, and how well you recover—work together.

Lifting weights makes your muscles bigger, and the main reason is how much total work you do—like how heavy the weights are, how many sets and reps you do, and how long you hold the tension. More total work = bigger muscles.