Asymmetry In Single Leg Vertical Countermovement Hop Kinematics In Collegiate Female Soccer Players

Abstract

Multidirectional sports such as soccer have a high incidence rate of anterior cruciate ligament injury. Asymmetries between limb have been linked to such non-contact injuries, thereby outlining the importance of screening measures that may identify at-risk groups. Specifically, tasks such as a vertical single leg countermovement (SLC) jump can provide an objective measure of frontal and sagittal plane asymmetries. PURPOSE: To identify lower limb asymmetries during a SLC jump. METHODS: 25 collegiate female soccer players (height: 167.4 ± 6.0 cm, mass: 67.16 ± 6.6 kg) completed 3 maximum SLC jumps on each limb. The side with the highest average jump height was defined as the high performance (HP) side and compared to the low performance side (LP). An 8 camera markerless motion capture system was utilized to analyze kinematic data at peak knee flexion during both the takeoff (TO) and landing (LN) phase using advanced machine learning. Force platforms measured the peak takeoff and landing vertical ground reaction force (GRF). A two-factor repeated measures ANOVA (p < 0.05) was used to determine differences between side (HP, LP) and phase (TO, LN) during the SLC task. RESULTS: 52% of the players had greater jump performance on their preferred kicking side. A main effect of side (p = 0.035) and phase (p < 0.001) was found for knee flexion (HP: TO 67.2 ± 7.2°, LN 60.5 ± 10.8°; LP: TO 65.0 ± 6.5°, LN 58.8 ± 7.2°). Likewise, a main effect of side (p < 0.001) and phase (p < 0.001) was found for GRF (HP: TO 1373 ± 236 N, LN 2238 ± 435 N; LP: TO 1341 ± 224 N, LN 2088 ± 280 N). A phase main effect was found for both hip flexion (p = 0.002) (HP: TO 49.8 ± 10.9°, LN 42.5 ± 11.9°; LP: TO 50.8 ± 10.1°, LN 41.0 ± 12.8°) and adduction (p = <0.001) (HP: TO 8.1 ± 4.4°, LN 5.5 ± 4.9°; LP: TO 8.7 ± 3.8°, LN 5.1 ± 5.7°). Significant main effects were not present for knee abduction (p > 0.05). CONCLUSIONS: Collegiate female soccer players demonstrate greater knee and hip flexion and hip adduction occur during the take-off phase of the single leg vertical jump compared to the landing phase. Additionally, the leg with greater performance has increased knee flexion during both take-off and landing which corresponds to greater peak force. These identified asymmetries between phase and limb could be considered important factors in monitoring potentially at-risk populations.