Differences in self-organizing patterns between acceleration and maximum velocity phases in sprinting: A pilot study based on muscle synergy analysis

In the framework of the ecological-dynamic approach, muscle synergies represent the inherent self-organizing mechanisms that emerge from the interaction between an individual and their environment, driving them toward achieving specific goals. These synergies simplify motor control by reducing complexity stemming from the presence of numerous degrees of freedom. This enables the system to adjust to changing environmental demands while maintaining stability in performance. As a result, studying muscle synergies has become a widely recognized approach for understanding neuromuscular control across various motor tasks in recent decades. Nevertheless, despite extensive research on muscle synergies during running at different speeds, no investigations have explicitly compared muscle synergies during the acceleration phase with the maximal velocity phase of a sprint. This pilot study aims to fill this gap in the literature by analyzing muscle synergies in both phases. To test the hypothesis positing that the neuromuscular system uses different self-organizing strategies in accordance with the specific goals of the two primary phases of a sprint, three male subjects performed three maximal 30-m sprints. During these sprints, electromyographic signals were recorded from eight muscles of the dominant lower limb. The data were analyzed using non-negative matrix factorization (NMF) to extract muscle synergy modules. The findings demonstrate that the neuromuscular system uses three synergy modules during the acceleration phase and two during the maximal velocity phase. This disparity suggests that the system tailors its self-organizing patterns to the different objectives of the two sprint phases. These findings may help coaches select exercises that ensure optimal training transfer. Future research should expand the sample size and examine the impact of environmental factors on self-organizing patterns during maximal sprints on a track compared to other field types.