Shared muscle synergies between running and physical performance tests

Understanding whether commonly used physical performance test (PPT)-related tasks replicate the neuromechanical characteristics of running is essential for informing return-to-running (RTR) decisions. PPTs are frequently used in rehabilitation, yet their ability to reflect the neuromuscular demands of running has not been fully established. This study therefore investigated the extent to which muscle synergies are shared between running and various PPT-related tasks to evaluate the neuromechanical replicability of these tasks.

Ten healthy male participants were recruited, performing running and nine PPT-related tasks including walking, single-leg hops (30, 60 and 100% of their maximum distance), single-leg squats, and various balance tasks. The activities in sixteen lower limb and trunk muscles were recorded. The data were analyzed using non-negative matrix factorization to explore shared muscle synergies between running and PPT-related tasks. The percentages of shared synergies and temporal patterns were compared between running and each PPT-related task.

All PPT-related tasks exhibited shared muscle synergies with running. However, walking (75% [40%-100%]), single leg hops with 30% of maximum distance (60% [20%-100%]), and step-up-down (63% [0%-100%]) demonstrated significantly higher percentages of shared synergies compared to other tasks. However, significant differences in temporal patterns were observed between running and all PPT-related tasks.

Walking, SLH30, and step-up-down tasks share a substantial proportion of muscle synergy patterns with running and appear to more closely reproduce the coordination strategies used during running. These tasks may therefore be promising candidates for future studies aimed at evaluating the predictability of safe return to running.