Lifting weights, using machines, or doing static holds all seem to build leg and arm muscles just as well — there's no proof that one way is better than the others for getting bigger muscles.

If you lift weights the same amount and with the same effort, holding your muscles still (isometric) builds muscle just as well as moving them up and down (dynamic).

Even though lifting weights makes your muscles bigger and more active, those changes don’t explain why you get stronger—meaning something else, like how your nerves coordinate movement, might be more important.

Even though lifting weights makes your muscles bigger and more active, those changes don’t explain why you get stronger at dynamic movements but not at holding static positions — something else, like how your brain coordinates movement, might be more important.

All three types of muscle movements—squeezing, lengthening, and holding—can help build muscle in your thighs and arms just as well, as long as you train hard and often enough.

Even though your muscles get bigger and fire more during weight training, those changes don’t explain why you get stronger at dynamic movements but not static holds—something else, like how your brain coordinates the movement, is more important.