Different neuromuscular parameters are associated with knee abduction and hip adduction angles during functional tasks

Knee abduction and hip adduction during functional tasks may indicate increased joint injury risk and discriminate between pathological and healthy people. Muscles’ neuromuscular variables such as amplitude (EMG_AMP) and onset (EMG_ONSET) have been used to explain kinematics. The study aimed to evaluate the correlation between two EMG variables of seven trunk and lower limb muscles and 3D kinematics during two tasks. Eighteen physically-active women participated in the study. The following variables were obtained during single-leg squat and anterior step-down: (i) EMG_AMP and EMG_ONSET of fibularis longus (FL), tibialis anterior (TA), vastus medialis (VM), biceps femoris (BF), gluteus medius (GMED), ipsilateral (OB_IL) and contralateral (OB_CL) external obliques and (ii) knee abduction and hip adduction angular displacement (initial angle – angle at 60° of knee flexion). Spearman’s correlation coefficient was calculated between kinematic and EMG variables. Greater knee abduction was correlated with delayed TA_ONSET, GMED_ONSET and OB_IL_ONSET during step-down. Greater hip adduction was correlated with lower VM_AMP, BF_AMP and delayed VM_ONSET during step-down. Although task-specific, these results suggest that EMG_ONSET may influence knee abduction, while both EMG_ONSET and EMG_AMP may affect hip adduction. The identification of muscle activation patterns in relation to kinematics may help the development of injury prevention and rehabilitation programs.