Most of the reason why people gain muscle at different rates isn't because of their genes—it's because of things they can change, like how hard they train, how much they eat, and how focused they are in the gym.

Adding just one or two extra sets of exercise per week probably won’t make your muscles grow any more, because everyone’s body reacts differently and it’s hard to measure tiny changes accurately.

Some people’s muscles grow a lot with training, others don’t—but if one person’s arms grow, their legs usually grow similarly, meaning your body’s natural response is more important than which muscles you train.

People grow muscle at very different rates — but each person tends to grow their arms and legs similarly, no matter what weight they use. This means your genes and biology matter more than how heavy your weights are.

Some people’s muscles grow a lot with training, others don’t—but if one person’s arms grow, their legs usually grow similarly, meaning your body’s natural response is more important than which muscle you train.

Everyone’s body responds differently to workouts—what works wonders for one person might be too much or too little for another, because of differences in genes, energy use, and how fast they recover.