Analysis Of Children's Crawling Movement Based On Time-Varying And Synchronous Synergy Theories

Crawling plays an important role in body and mind development for the infants before they can walk.The ability to walk depends on the ability to crawl,therefore,crawling assessment is an important method to evaluate the motor function for children with brain injury.Cerebral palsy(CP),which is a common brain injury disease,greatly affects the physiological and psychological development of the patients.The early assessment and treatment for CP patients can alleviate their motor function abnormalities,and bring hope to their life.Currently,gait analysis and reaching and grasping analysis are the most common evaluation methods of the motor ability for CP patients.However,crawling evaluation,which contains the information about the whole body muscle coordination,were rarely explored among CP patients.In addition,the current analysis of crawling focused on kinematics analysis,such as video,pressure and acceleration,rather than electromyographic signals,which reflect the motion control mechanism of central nervous system.In view of the shortcomings in the current research,this study aims to comprehensively analyze the crawling movement from the angles of kinematics,muscle co-activation,and muscle synergy.In particular,the study explored the possibility of using two muscle synergy analysis methods,which are synchronous(SYN)synergy and time-varying(TV)synergy,in assessing crawling dysfunction.The main works and achievements can be summarized as follows:(1)Nine healthy children and 11 children with CP were enrolled to conduct a hands-and-knees crawling experiment.During the crawling process,the pressure signals of the left hand and the left knee,as well as the electromyographic signals of 12 muscles on both sides of the upper body were collected.(2)Kinematic characteristics of the hands-and-knees crawling,including stance phase and swing phase ratio,ipsilateral phase lag,and inter-limb coordination patterns,were analyzed for the healthy children and the cerebral palsy children respectively.It was found that the stance phase ratio was significantly higher than that of swing phase ratio,and the inter-limb coordination was dominated by no limb pairing regardless of healthy subjects or cerebral palsy subj ects.(3)Muscle co-activation analysis was performed on the biceps femoris-triceps and latissimus dorsi-triceps using two different muscle co-activation coefficients metrics.It was found that the co-activation coefficients could be adopted to quantitatively analyze the relative activations between muscles in crawling.(4)Muscle synergy analysis of the hands-and-knees crawling was carried out for the healthy group and the CP group using two different methods.It was found that no matter which method was used,two muscle synergies could be extracted on each side,and one synergy was mainly activated in the stance phase,and the other synergy was mainly activated in the swing phase.Furthermore,two synergy analysis methods were compared from the perspectives of synergy symmetry,synergy repeatability,inter-subject synergy similarity and synergy co-activation.It was found that:1)SYN synergy method could describe the synergy symmetry better than the TV synergy method,while TV synergy method had a better performance in distinguishing cerebral palsy subjects from abnormal synergy symmetry.2)Two synergy methods had their unique advantages in assessing the repeatability of crawling movements and both methods could be used for repeatability analysis.3)As for inter-subject synergy similarity,compared with TV synergy method,SYN synergy method provided a possible way to quantitatively evaluate the crawling dysfunction in cerebral palsy.Specifically,a standard synergy template could be extracted from the healthy people,and the evaluation of crawling abnormities could be done in terms of SYN synergy structure or synergy activation patterns.4)SYN synergy method showed more synergy co-activation,and the co-activation coefficient of the stance phase was significantly higher than that of the swing phase comparing with the TV synergy method.