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 do blood flow restriction training—like wearing tight bands on your arms or legs while lifting light weights—you build muscle mainly because your muscles fire harder and earlier, not because of the burn or buildup of waste products.

You can build muscle just as well by lifting light weights with your blood partially squeezed off, as you can by lifting heavy weights—so maybe it’s not the weight itself that matters most, but how much your muscles burn and swell up.

You can make your muscles grow bigger by lifting very light weights if you restrict blood flow to your arm or leg — it tricks your body into thinking you’re lifting heavy.

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 you do BFR training, your muscles grow more in the middle and lower parts of your thigh than near your hip — meaning the effect is strongest where the blood flow is most restricted.