The major muscles involved while performing a wall sit or squat are the quadriceps muscles.
Explanation:
Exercises like wall sit or squat are an isometric exercises which works the entire group of lower body muscles.
Isometric exercises are endurance building exercises which improves the muscle endurance by holding it in a position for longer time. These exercises does not involve any big bodily movements but works by tensing the muscles.
Both these exercises primarily involve the front thigh muscles or the quadriceps. Squats and wall sits help to tone and shape the quads and other muscles involved. The angle of the body should be maintained at right angle to reduce the pressure on these muscles.
Other muscles which are involved in these exercises are the hamstrings, core, lower back muscles etc.
