Leg Muscle Percentages by Angle in Squats

The squat is considered a gold standard when it comes to lower body exercises. In fact, fitness professionals certified with the American Council on Exercise ranked squats as their favorite lower body exercise. It’s not surprising considering the squat targets your quadriceps as well as your glutes, hamstrings, and calf muscles. To what percentage these leg muscles are activated is determined by the joint angles you assume for your squat.

Execution

To perform a squat, stand with your feet shoulder-width apart. Exhale and slowly push your hips back as you bend your knees until you are in a seated pose. Pause briefly and extend your knees and hips to return to the starting position. You can perform the squat so that your knee is flexed at different angles. When your knees are bent at a 40-degree angle, it is considered a partial squat; a 70- to 100-degree angle is a half squat and anything greater than a 100-degree bend is a deep squat. Each different angle affects how your muscles respond to the exercise.

Quadriceps

The squat primarily strengthens the quadriceps muscles regardless of your knee flexion angle. A study published in the "Journal of Orthopaedic and Sports Physical Therapy," however, found that quadriceps activity peaks at 90 degrees of flexion, with the quadriceps muscles vastus medialis showing 87.6 percent activation and the vastus lateralis showing 86.7 percent activation. Deeper squats actually produced less quadriceps activity. At 150 degrees of flexion, the vastus medialis activation was reduced to 82.3 percent and the vastus lateralis activation went down to 80 percent.

Glutes

While the glutes are only synergist or secondary muscles in the squat exercise, you can increase how much you target them by deepening your squat. According to a study published in the "Journal of Strength and Conditioning Research," glutes are activated at 16.9 percent during a partial squat, 28 percent during a parallel or half squat and 35.4 percent during a full or deep squat.

Hamstrings

Like the glutes, hamstrings are considered secondary muscles during the squat exercise because they only serve as dynamic stabilizers. Unlike the glute and quadriceps muscles, however, hamstring activation does not appear to be affected by squat depth. A study published in the "Journal of Strength and Conditioning Research" found no significant difference in peak and mean torque between full, partial and parallel squats.