Dynamic Correlation Between Muscle Synergy And Motor Performance During The Special Learning Process Of Basic Rope Skipping

Objective:The relationship between the internal structure of muscle synergy and the external motor performance is still unclear in motor learning and development.To further understand the characteristics of muscle synergy's development,we select the rope skipping movement with high requirements of whole body participation and synergy as the research object.The goal of this study is to investigate in detail the evolution of muscle synergy's structure in motor development,the dynamic correlation with motor performance,and the difference of muscle synergy in different rope skipping movements.Methods:16 students?age 19-20,height 161-183 cm,weight 46.5-91 kg?from 2018 rope skipping special class were selected and tested in three times with identical contents.At the time point of three tests,the students have completed four months,eight months and 11 months of special training.The test actions are the basic rope skipping action including Basic Jump,Alternate Foot Step Jump and Double-Under Jump;each action lasts for 20 seconds,and is done twice.The experiments were carried out by using Vicon motion capture system,Kistler three-dimensional force measuring platform and Delsys wireless surface electromyography acquisition system to measure kinematics,ground reaction force and the surface electromyographical signals of 8 representative muscles?long head of biceps femoris,medial femoris,medial gastrocnemius,triceps brachii longhead,flexor brachii,flexor carpi ulnaris,lateral gastrocnemius and anterior tibial muscles?of ankle,knee,wrist and elbow joints.None negative matrix decomposition?NMF?was used to extract muscle synergy,and cluster analysis was used to classify it.After the performance indexes were determined using analysis of variance?ANOVA?or rank sum test,the correlation between muscle synergy structure and performance indexes and the change with performance level were observed using correlation analysis.Results:1)In Basic Jump,the average activation intensity of muscle synergies decreased with the increase of motor performance(F=3.501^**,^**P<0.01,^*P<0.05,#no significance).The correlation between gastrocnemius and flexor carpi ulnaris?-0.489^*to#?,and triceps brachii(-0.696^**to#)diminished,and flexor carpi ulnaris enhanced(#to-0.649^**).2)In Alternate Foot Step Jump,the correlation between extending elbow and biceps femoris long head strengthened?#to-0.481^*?.The negative correlation between medial femoral and flexing elbow strengthened(#to-0.584^**).The negative correlation between anterior tibial muscle and biceps femoris long head?#to-0.588^*?strengthened.3)In Double-Under Jump,the activation correlation both within the muscles of the lower limbs and between the muscles of the upper and lower limbs is generally enhanced.In the process of improving the performance of the Double-Under Jump,the lateral fibular muscle was positively correlated with the anterior tibial muscle(from#to r=0.653^**),and negatively correlated with the medial fibular muscle(from#to r=-0.58^**).In elbow flexion synergy 5,which was mainly activated by flexor brachii,the negative correlation between flexor ulnaris carpi and flexor brachii?from#to r=-0.482^*?,biceps femoris?from#to r=-0.435^*?,and medial fibular muscle(from R=-0.648^**to#);the negative correlation between triceps brachii and medial femoral muscle?from R=-0.471^*to#?.4)The connection of muscle synergy between different movements.In the 10th cluster,the correlation between the flexor carpi ulnaris and triceps brachii,which are the most active muscles,remained strong(-0.879^**to-0.965^**).The second strong correlation changed with movement,from fibular and fibular?r=-0.640^*?,fibular and tibial anterior?r=-0.711^*?,to biceps femoris and tibial anterior?r=-0.448^*?,to biceps tibialis and medial fibular?r=-0.550^*?,tibial anterior and lateral(r=-0.491^**).Conclusions:In this study,with the improvement of motor performance,the muscle synergies of different actions changed significantly,and the pattern of neuromuscular activation of the trainees changed slowly and steadily.Muscle activation amplitudes decreased slightly,the division of labor of muscle gradually strengthened,the correlation between muscles gradually differentiated.Increasingly,the functional characteristics of muscle synergy strengthened.The relationship of the synergies in these actions reflects the structural relationship between the actions.