Muscle Synergies Analysis Shows Altered Neural Commands In Women With Patellofemoral Pain During Walking

BackgroudSeveral studies suggest that the central nervous system coordinates muscle activation by modulating neural commands directed to groups of muscles combined to form muscle synergies. Individuals with patellofemoral pain (PFP) move differently from asymptomatic individuals. Understanding the neural factors involved in the execution of tasks such as walking can help comprehend how the movement is planned and better understand this clinical condition. Research questionTo compare the muscle coordination of women with and without PFP during gait. MethodsEleven women with PFP and thirteen asymptomatic women were assessed using three-dimensional kinematics and electromyography (EMG) while walking at self-selected speed. Kinematics of the trunk, pelvis and lower limbs were analyzed through the Movement Deviation Profile. Muscle synergies were extracted from the EMG signals of eight lower limb muscles collected throughout the whole gait cycle. ResultsKinematic differences between the two groups (p<0.001, z-score=3.06) were more evident during loading response, terminal stance, and pre-swing. PFP group presented a lower number of muscle synergies (p=0.037), and greater variability accounted for (VAFtotal) when using 3 (p=0.017), 4 (p=0.004), and 5 (p=0.012) synergies to reconstruct all EMG signals. The PFP group also presented higher VAFmuscle for rectus femoris (p=0.048) and gastrocnemius medialis (p=0.019) when considering 4 synergies. SignificanceOur results suggest that women with PFP show lower motor complexity and deficit in muscle coordination to execute gait, indicating that gait in PFP gait is the result of different neural commands compared to asymptomatic women.