You don’t need to push to absolute failure to grow your thigh muscles — stopping just before failure works just as well and leaves you less tired, making it easier to train consistently.

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.

If you lift weights until you can't do another rep, or stop just before failure, your thigh muscles grow about the same amount after eight weeks — but stopping short feels less exhausting each time.

Stopping a few reps short lets you do about the same total amount of work over weeks as going all the way to failure — because you can recover faster and do more sets without burning out.

Lifting weights until you can't do another rep leaves you much more tired during and after the workout than stopping a few reps short — even if both methods build muscle equally.

If you lift weights until you literally can't do another rep, you'll feel more tired right after than if you stop a couple reps before failure — even if you're someone who regularly lifts weights.