Not all thigh muscles respond the same way — one part might grow a bit better with stopping short, while another grows a bit better with pushing to failure.

Muscles don’t grow evenly—when you train your thigh, the top and middle parts of the front muscle grow more than the bottom, and the side muscle grows the same everywhere.

If you're already used to lifting weights, training until you can't do another rep gives you about the same muscle growth as stopping a few reps short—so you don't have to push to absolute exhaustion to build muscle.

You don’t need to push your muscles to absolute exhaustion to grow them—working them pretty hard (but not all the way to failure) might give you just as much muscle growth as going all out.

Muscles don’t grow evenly — some parts get bigger than others, and different muscles in the thigh respond differently to the same exercise.

If you lift weights until you're almost too tired to do another rep, you'll likely build bigger muscles—but your strength gains won't be any better than if you stopped earlier, as long as you're doing the same total amount of work and lifting the same weight.