Title: Does Squat Depth and Width Influence Hip and Knee Joint Moments?
Abstract: Squats are a popular closed-chain exercise that can benefit strength, power, balance, and range of motion. Proper squat technique includes varying depths and widths. PURPOSE: This study investigated sagittal plane knee and hip moments during 9 different squat variations. METHODS: 10 healthy, college-aged adults (7 female, 3 male, mass = 67.4 ± 10.7 kg; height = 1.68 ± 0.08 m) performed body-weight squats at 3 widths (standard (shoulder width), wide (150% of shoulder width), and widest (200% of shoulder width)) and 3 squat depths (shallow (55 degree knee flexion), parallel (90 degree knee flexion), and deep (125 degree knee flexion)). Anthropometric, marker coordinate, and force data were combined to calculate peak hip and knee moments during the eccentric (downward) and concentric (upward) phases of the squat. 2x3 ANOVAs were used to evaluate the effect of squat depth and width on peak hip and knee eccentric and concentric moments. RESULTS: Generally, concentric and eccentric hip and knee moments increased with greater squat depth and decreased with greater squat width. At the deep depth, the eccentric moments for the wide and widest stance widths were significantly less when compared to the standard width at the knee (standard = 1.23 ± 0.29 Nm/kg, wide = 1.09 ± 0.21 Nm/kg, widest = 0.98 ± 0.15 Nm/kg; p < 0.01) and at the hip (standard = 0.99 ± 0.21 Nm/kg, wide = 0.89 ± 0.19 Nm/kg, widest = 0.78 ± 0.17 Nm/kg; p < 0.001). At the parallel depth, the eccentric hip moment for the widest stance width (0.78 ± 0.13 Nm/kg) was significantly less than the eccentric hip moment for the standard (0.94 ± 0.18 Nm/kg) and wide stance widths (0.90 ± 0.14 Nm/kg; p < 0.01). The knee concentric moment for the deep depth was significantly less at the widest stance width (1.07 ± 0.20 Nm/kg) when compared to the wide (1.19 ± 0.21 Nm/kg) and standard stance widths (1.30 ± 0.28 Nm/kg; p < 0.01). CONCLUSIONS: Squat depth and stance width influence hip and knee joint moments, and both should be considered when performing a squat. If deep squats are used to increase lower-extremity muscle activation and overall work, increasing stance width will reduce sagittal plane hip and knee moments and possibly joint loads. Further research is needed to investigate other methods of reducing lower-extremity joint load while exercising.