When untrained men do a specific type of weight training called pre-exhaustion, some parts of their thigh muscles grow more than others—the lower front part grows 44% thicker and the upper outer part...

A specific type of weight training makes leg muscles grow unevenly, with some parts growing much more than others, because different parts of the muscle get worked harder during the exercise.

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.

Among people who regularly lift weights, training until muscle failure for eight weeks leads to about the same increase in quadriceps muscle thickness as training with a small amount of reserve strength left, with both methods producing an average gain of 0.18 centimeters.

This study only looked at the front and side of the thigh—so we don’t know if doing more sets helps your front thigh or hamstrings grow more.

Eight weeks of moderate-intensity weight training increases muscle thickness in the chest, biceps, and thigh muscles by 5–10% in men who have not trained before, even if they do not train to muscle failure in every set.