VARIABILITY OF TECHNICAL ACTION COORDINATION STRUCTURE IN BOXING AT FATIGUE
One of the directions of research into movement variability studies it at changing external or internal conditions during motor task performance. The results of such investigations are ambivalent even when analysing movements with similar kinematic structure. The aim of the research was to study the variability of skeletal muscle bioelectric activity and space-time characteristics of various punches in boxing at fatigue. Six highly skilled boxers of different weight classes were involved. We analysed parameters of variation of muscle electromyographic activity, distance and speed of the anthropometric points of body segments, as well as joint movement amplitude under regular conditions and after an aerobic motor load. We found low amplitude variability in most of the skeletal muscles under study, both in regular conditions and after a motor load. At fatigue, amplitude variability of almost all muscles decreased. Under regular conditions, the movement amplitude of the shoulder, elbow and hip joints on the bodyʼs right side was more varied than that in the joints on the left. After a motor load, changes in the variability of joint movement amplitude during the performance of different punches were dissimilar. The most variable were changes in the angles of the right side of the body, especially the elbow and hip joints, when performing a direct punch. The least changes under the load were observed in the movement amplitude of the elbow and hip joints on the left side. Thus, variability changes in kinematic parameters caused by skeletal muscle activity are a mechanism for maintaining stability of motor task performance. Presumably, the central neural control of complex coordination movements in boxers when performing punches is carried out through the formation of kinematic and muscle synergies. More research is needed to clarify the mechanism of formation and functioning of kinematic synergies and their variability.