The Muscle's Force in a Squat

Although the squat is often touted as an overall lower body exercise, it does not target all the leg and hip muscles equally. In fact, several of the large leg muscles are barely active during the squat exercise. Using squat variations changes the muscle force involved in the squat exercise, but only slightly. It does not affect the primary muscle emphasis of the exercise.

  1. Squat Exercise Technique

    • In order to get the most benefit from the squat exercise, you have to do it correctly. The most common mistake is to initiate the movement by bending your knees, which places undue stress on your knee joints. You should start the descent by pushing back your hips, called hinging at the hips. This shifts your weight back on your heels, allowing you to sit back as if sitting down into a chair. Continue descending until your thighs are about parallel to the floor.

    Primary Movers

    • The quadriceps muscles are the primary movers and exert the most force during the squat exercise. The vastus lateralis, vastus intermedius, vastus medialis and rectus femoris are the four muscle heads that make up the quadriceps. The muscles originate on the femur, the upper thigh bone, cross the knee joint and attach to the tibia, a bone in the lower leg. The quadriceps are primarily responsible for straightening the knee joint.

    Secondary Movers

    • Several muscles in the lower body, including the glutes, hamstrings, lower back muscles and inner thigh muscles are involved in the squat exercise as secondary movers; they assist in the movement, but do not exert as much force as the quadriceps muscles. The hamstrings are only involved as stabilizer muscles and do not significantly contribute to the muscle force during the squat exercise. A study published in the "Journal of Medicine and Science in Sports and Exercise," found that the hamstrings were minimally active during an unloaded squat.

    Squat Variations

    • Contrary to gym lore, wide stance squats do not target the inner thighs more and deep squats do not target the hamstrings more. A wide stance or deeper squat increases the activity of the glute muscles, but doesn't affect the activity of the quadriceps, hamstrings or inner thigh muscles.