When you lift weights and your muscles get bigger, the number of special repair cells and nuclei inside them tends to go up a bit — but that’s not the whole story; other things are also helping your muscles grow.

Even when you train one leg differently from the other, both legs tend to grow muscle in similar ways — which means your body’s natural biology, not the workout itself, is what really controls muscle growth.

If you're already fit and lift weights, your muscle cells don't seem to add more helper cells or nuclei, even when you change up your routine—meaning those extra cells might not be needed to make your muscles bigger.

Getting stronger from lifting weights doesn’t always mean your muscles are getting bigger—and vice versa. Strength and size don’t go hand in hand.

Getting stronger from lifting weights doesn’t always mean your muscles are getting bigger—and vice versa. Strength and size don’t go hand in hand.

When people lift weights, how much their muscles grow depends way more on their own body than on the type of workout they do—because even when people switch up their routines, their muscle growth stays pretty much the same.