When your muscles swell up from fluid buildup during a tough workout, that pressure might send signals to your cells to grow bigger — even if you’re not lifting heavy weights.

When your muscles swell up from the burn during a workout, that puffiness might trick your cells into thinking they’re being stretched, turning on growth signals — like a fake workout signal.

When you wrap your arm tightly and lift light weights, your muscles still grow — and your body turns on the same growth signals as when you lift heavy weights, which hints that the burning feeling might be key.

When you lift weights, the pulling force on your muscles is what makes them grow bigger—not hormones or feeling tired. This force turns on internal signals that tell your muscles to make more protein and get larger over time.

When you lift weights, the physical pull on your muscles is the main reason they grow bigger — not because of hormones or feeling tired or burned out.

When you lift weights until your muscles burn and feel fatigued, the buildup of waste products might help your muscles grow bigger, but the main reason they grow is still from the physical force you're using.