Effects of Squat Depth and Stance Width on Lower Extremity Frontal Plane Kinetics

Abstract

The squat is an exercise commonly used to improve lower-extremity (LE) strength and performance. Repeated frontal plane movement in the LE could have detrimental effects by contributing to certain joint pathologies. Therefore, investigating squat technique on LE kinetics is warranted. PURPOSE: This study compared hip and knee frontal plane kinetics during body-weight squats with varying depths and stance widths. METHODS: 11 healthy, college-aged participants (6 female, 5 male, height = 1.68 ± 0.08 m, mass = 67.4 ± 10.7 kg) performed 5 body squats at 100%, 150% and 200% of shoulder width for each of the following knee flexion angles: 55°, 90° and 125°. Trials were randomized and data were collected using Vicon Nexus and AMTI force plates. Frontal plane kinetics were processed using Visual 3D. RESULTS: At the hip, adduction moments showed significant increases as the width (100% = 0.301 ± 0.02, 150% = 0.539 ±0.04 and 200% = 0.736 ± 0.04; p < 0.001) and depth (55° = 0.306 ± 0.03 Nm/kg, 90°= 0.545 ± 0.04 Nm/kg and 125° = 0.725 ± 0.05 Nm/kg, p < 0.001) increased. At the knee, adduction moments significantly increased with wider stances (100% = 0.116 ± 0.02 Nm/kg, 150% = 0.178 ± 0.01 Nm/kg and 200% = 0.221 ± 0.01 Nm/kg; p < 0.001) while greater knee abduction moments were observed as depth of the squat increased (55° = 0.006 ± 0.02 Nm/kg, 90° = 0.147 ± 0.04 Nm/kg and 125° = 0.465 ± 0.05 Nm/kg; p < 0.001). CONCLUSION: Deep squats and larger stance widths may place greater demand on the hip and knee joints as evidenced by increased frontal plane moments. These data may benefit rehabilitation and strength training programs. For example, clinicians using squats as a rehabilitative exercise might decrease stance width when aiming to avoid LE frontal plane joint loading. Further, athletes who repeatedly stress the frontal plane stabilizing structures of the LE during dynamic movements may benefit from deeper and wider squats in training that would prepare these structures for their sport specific movements. Further research is needed to investigate other means of altering joint loading in the LE during exercise.