A Biomechanical Review of the Squat Exercise: Implications for Clinical Practice

Abstract

The squat is one of the most frequently prescribed exercises in the rehabilitative setting. Performance of the squat can be modified by changing parameters such as stance width, foot rotation, trunk position, tibia position, and depth. An understanding of how the various squatting techniques can influence joint loading and muscular demands is important for the proper prescription of this exercise for various clinical conditions. The purpose of this clinical commentary is to discuss how the biomechanical demands of the squat can be influenced by various modifiable parameters. General recommendations for specific clinical conditions are presented.

Level of evidence: 5.

Keywords: biomechanics; clinical commentary; kinematics; kinetics; squatting.

Figure 1.. Sagittal plane orientation of the trunk influences the external moments at the hip and knee.

1. Squatting with the trunk in a more upright position increases the knee flexion moment while decreasing the hip flexion moment. (B) Moving the trunk forward increases the hip flexion moment while decreasing the knee flexion moment.

Figure 2.. Forward inclination of the trunk that is achieved by spine flexion (A) results in decreased tolerance to compressive loads and less control of anterior shear forces as compared to when forward trunk inclination is achieved with a neutral spine position (B).

Figure 3.. Sagittal plane orientation of the tibia influences the external moment at the knee.

1. Squatting with the tibia in a more upright position decreases the knee flexion moment. (B) Moving the tibia forward increases the knee flexion moment.

Figure 4.. Squatting to a depth that exceeds available hip flexion results in a posterior pelvic tilt.

Figure 5.. Trunk-tibia angle (bottom left).

1. Hip extensor bias with trunk-tibia angle > 10°; (B) Knee extensor bias with trunk-tibia angle < -10°; (C) Neutral bias with -10° $\le$ trunk-tibia angle $\le$ 10°.