Author(s): SAITO, H., YAMANO, A., SUZUKI, N., MATSUSHITA, K., YOKOYAMA, H., JOACHIM, V.C., NAKAZAWA, K., Institution: TOKYO UNIVERSITY OF TECHNOLOGY, Country: JAPAN, Abstract-ID: 771

INTRODUCTION:
Single leg hops (SLH) are a vital measure for evaluating the readiness of athletes to return to sports post-injury. The efficacy of SLH is based on its indication of adequate lower limb movement and stability, which is essential for a variety of sports activities. This study investigated the differences in muscle synergies in trunk and lower limbs during SLH at 30% (SLH30) and 100% (SLH100) of maximum distance to understand the neuromechanical mechanisms underlying the high performance of SLH.
METHODS:
Ten healthy males were recruited for the study. During the SLH30 and SLH100 tests, unilateral surface EMG data were collected from 15 muscle groups in the trunk and lower limbs. Non-negative matrix factorization (NMF) was employed to extract the muscle synergies.
RESULTS:
The number of muscle synergies observed in SLH100 was significantly higher than in SLH30 (p = 0.0078, effect size = 1.28). Median values were 4.0 (3.0 – 5.0) for SLH30 and 5.0 (4.0 – 6.0) for SLH100. The cluster analysis identified four muscle synergies shared between SLH30 and SLH100, with a distinct non-knee related synergy emerging in SLH100.
CONCLUSION:
Interventions targeting SLH performance should consider muscles linked to the synergy specific to SLH100, especially in individuals with sports-related injuries. Shared synergies between SLH30 and SLH100 represent a foundational neuromuscular control strategy, while a distinct synergy exclusive to SLH100 plays a role in facilitating longer single-leg hops. The synergy specific to SLH100 represents the neuromechanical output for extended forward jumps. However, the presence of a distinct synergy in SLH100, associated with non-knee muscles, suggests potential limitations of SLH in evaluating knee-specific functions.