Influence of Testing Position on Hip Torque and Relationships with Frontal Plane Kinematics in Females

Abstract

The relationship between hip extension, abduction, and external rotation torque has been correlated to frontal plane biomechanics during functional tasks like the single leg squat. Altering testing position has been identified to influence torque output for hip extension, abduction, and external rotation. However, comparing the relationship between hip torque at different testing positions and frontal plane hip and knee squatting kinematics has yet to be evaluated. PURPOSE: To assess the influence of testing position on hip extension, abduction, and external rotation torque in females and relationships to frontal plane squatting kinematics. METHODS: Isometric hip torque was assessed in 19 college aged females at varying degrees of hip flexion. Torque was assessed with hand-held dynamometry for hip extension (0, 45, and 90 degrees of hip flexion); hip abduction (-5, 0, and 45 degrees of hip flexion); and hip external rotation (0, 45 and 90 degrees of hip flexion). Five single leg squats were also completed for 2-dimensional analysis of frontal plane hip and knee kinematics. Repeated measures ANOVAs were used to evaluate differences in hip torque across testing positions. Relationships between hip torque and frontal plane hip and knee kinematics during a single leg squat were explored with correlations. Significance was set at p<.05. RESULT: Greater torque was seen during hip extension at 90 degrees of hip flexion (0.74±0.25Nm/kg*m) compared to both 0 (0.43±0.14Nm/kg*m) and 45 (0.50±0.19Nm/kg*m) degrees of flexion (p<.001). A significant decrease in hip abduction torque was seen at 45 degrees of hip flexion (0.44±0.15Nm/kg*m) compared to both -5 (0.58±0.21Nm/kg*m) and 0 (0.63±0.24Nm/kg*m) degree testing position (p<.001). No differences in torque were seen for hip external rotation. Significant, positive, and moderate correlations were seen with hip extension torque and hip adduction kinematics at 90 degrees of hip flexion (r=.544, p=.016) compared to 0 (r=.490, p=.033) and 45 (r=.477, p=.039) degrees of hip flexion. No significant correlations were seen between squatting kinematics and hip abduction or external rotation torque. CONCLUSION: Testing position alters hip torque in healthy aged females but does not influence the relationship between torque and lower extremity kinematics of a single leg squat.