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...

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.

Muscles get bigger when they're put under tension during exercise - like when you lift weights. Only exercises that make your muscles work hard against resistance will help them grow.

Muscle growth occurs mainly due to the tension placed on muscles and the buildup of metabolic byproducts during exercise, not simply because of how heavy the weights are.

Lifting weights makes your muscles grow because the longer and harder you work them, the more they get the signal to build new muscle fibers.

Muscle growth occurs when muscles are subjected to mechanical tension during resistance training, and this tension can be created by lifting heavy weights for few repetitions or moderate weights for many repetitions, as long as the set is taken close to the point of inability to continue.