Biomechanical comparison of two squatting protocols in adolescents and young adults with femoracetabular impingement syndrome

Introduction Squatting is an important activity of daily living which can be particularly useful in the management of Femoroacetabular Impingement Syndrome (FAIS). However, double-leg squat protocols can vary significantly, potentially impacting biomechanical outcomes. A squat with a “hold” before the ascent phase represents one variation which increases muscular endurance demands and may elucidate such impacts. The purpose of this study was to identify biomechanical differences between a traditional squat (TSquat) and squat with a hold (HSquat) in adolescents and young adults with pre-operative FAIS. Methods Participants ( N = 46; 35 females; 16.5 ± 1.7 years) undergoing primary unilateral hip preservation surgery for FAIS completed two squat types assessed via 3D motion analysis. The TSquat was performed with descent immediately followed by ascent. The HSquat included a three second pause at participants’ lowest comfortable position. Joint range of motion, moments, powers, and squat depth in participants’ pre-operative limb were compared between each technique. Results Participants squatted lower in the TSquat than the HSquat (42.6% ± 12.8% vs. 36.0% ± 13.0%, p < 0.001). Maximum hip, knee, and ankle flexion were greater in the TSquat (mean difference: 4.2 ± 0.7°, 10.2 ± 1.2°, 1.4 ± 0.1°, respectively; p < 0.05). Peak sagittal moment at the hip/knee (mean difference: 0.10 ± 0.05 Nm/kg, 0.09 ± 0.08 Nm/kg, respectively; p < 0.001) and peak power generation at the knee (mean difference: 0.40 ± 0.16 W/kg; p = 0.001) were also greater in the TSquat. Discussion Participants with FAIS squatted to a shallower depth during the HSquat compared to the TSquat and displayed altered biomechanics, accordingly. Given these findings, greater standardization of squatting techniques is warranted as technique variations may affect outcomes, and researchers must consider potential adjustments made by those with FAIS in their natural squat movement.