Modular organization of intermuscular and interjoint interaction during ball catching

The aim of this study was to examine the organization of ball-catching movements with different biomechanical structures, which are among the profile elements in rhythmic gymnastics, based on common synergies. An additional goal was to identify specific synergies presumably formed during the performing of movements with increased coordinative complexity. Synergy parameters were derived from simultaneously recorded electromyographic (EMG) data from 16 muscles and joint angle kinematics; factor analysis and principal component analysis were applied. It was found that at the kinematic level, participants demonstrated similar motor control strategies for catching the ball. Interjoint coordination was structured into two modules, independent of the motor task's complexity. The specificity of kinematic modules manifested in a shift of the main peak of interjoint interaction synchronization, driven by the subjective perception of the ball contact moment. At the muscular level, up to five muscle modules were identified, two of which were consistently present across different ball-catching movements. Their function is associated with generating active motions of the upper limb segments and stabilizing the shoulder girdle. The component composition of muscle synergies is largely determined by the movements' biomechanical structure and the presence of a common subtask within them.