Correlation between muscle synergy characteristics of the affected leg and gait stability during walking in patients undergoing anterior cruciate ligament reconstruction
BACKGROUND:Existing studies have preliminarily summarized the potential association between muscle activity of the affected lower limb and gait stability during walking in patients undergoing anterior cruciate ligament reconstruction.However,there are some issues such as incomplete observation of muscle categories,incomplete observation of walking action phases,and failure to consider synergistic effects among multiple muscle groups,which urgently require further improvement in this study.OBJECTIVE:To monitor muscle synergy information of the affected leg during walking in patients undergoing anterior cruciate ligament reconstruction and to analyze the association between muscle synergy information and gait stability.METHODS:Twenty-four male patients aged(21.66±4.09)years undergoing anterior cruciate ligament reconstruction,were recruited.Electromyographic and center of pressure data were collected from the affected lower limb during walking.A non-negative matrix decomposition algorithm was used to extract the number of muscle synergic elements from the affected leg,the time spent in peak activation of each muscle synergic element,and the muscle relative weight indexes.Correlation analysis was then performed with the center of pressure indexes.RESULTS AND CONCLUSION:Six types of muscle synergies were identified in the affected leg.The number of muscle synergic elements showed no significant correlation with the distance and speed of lateral displacement of the center of pressure.Regarding the peak activation time of muscle synergic elements,synergic element 3 in the dominant gait loading response period showed a significant negative correlation with the lateral displacement distance of the center of pressure(r=-0.413,P=0.045)and a significant negative correlation with the lateral displacement velocity of the center of pressure(r=-0.470,P=0.020).The activation time of the remaining types of muscle synergic elements was not significantly related with patient's gait stability indices.In terms of muscle relative weights,the rectus femoris muscle of synergistic element 1 in the dominant gait loading response period showed a significant negative correlation with the lateral displacement distance of the center of pressure(r=-0.592,P=0.005)and a significant negative correlation with the lateral displacement speed of the center of pressure(r=-0.529,P=0.014).Additionally,the relative weight of the biceps femoris muscle of synergistic element 3 in the dominant gait loading response period showed a significant negative correlation with the lateral displacement distance of the center of pressure(r=-0.428,P=0.037).To conclude,the central system in patients undergoing anterior cruciate ligament reconstruction regulates the synergistic muscle activity of the affected leg during walking to enhance gait stability in two primary ways:by prolonging the activation time of the muscle synergists during the dominant loading response period and enhancing the activation of the quadriceps muscle,in order to enhance the control of eccentric contractions of the knee joint during the landing of the affected leg and improve the stability of the knee joint;and by increasing the activation of the biceps femoris muscle during the loading response period,which increases the degree of knee flexion and enhances the lower limb's cushioning function during the landing of the affected leg.