Comparative Analysis of Muscle Coordination Patterns During Squatting in Trained and Untrained Individuals

Squatting, a closed-kinetic chain exercise, requires the complex coordination of multiple muscles. However, the differences in muscle coordination patterns between individuals with varying levels of exercise proficiency remain unclear. This study aimed to compare muscle coordination patterns during the squat exercise between trained and untrained individuals. Sixteen participants, classified into trained and untrained groups, performed 20 repetitive squats while both motion capture and electromyography data were recorded. Muscle synergy analysis was employed to identify muscle coordination patterns, and cluster analysis was used to determine preferred muscle synergies within each group. The findings indicate that trained individuals exhibit muscle synergies characterized by the coactivation of trunk and leg muscles near the bottom position of the squat. By contrast, untrained individuals primarily show coactivation of leg muscles only. Motion analysis further revealed that trained participants maintained a more upright posture during this phase compared with untrained participants. The distinct muscle synergies between trained and untrained individuals suggest the importance of coordinated trunk and leg muscle activation in maintaining postural control near the bottom position, where the movement transitions from descent to ascent. These insights can inform training strategies to promote effective trunk-leg coordination and postural control in untrained individuals.