Comparison of stop-jump muscle synergies in amateur basketball players with and without asymptomatic patellar tendon abnormalities during simulated games

Asymptomatic patellar tendon abnormality (APTA) is considered a precursor to patellar tendinopathy (PT), but its pathogenesis remains unclear, especially regarding changes in muscle coordination. Therefore, it is essential to explore the muscle synergy patterns in individuals with APTA. Methods: This study recorded sEMG data during stop-jump tasks in 8 APTA and 8 healthy amateur male basketball players in a simulated basketball game. Muscle synergies were extracted using Non-Negative Matrix Factorization and K-Means clustering. Results: Three synergies were identified in both groups. In Synergy 1, tibialis anterior, semitendinosus and vastus lateralis weights primarily influenced the waveform. In Synergy 2, biceps femoris, vastus lateralis and medial gastrocnemius weights primarily influenced the waveform. In Synergy 3, peroneus longus, vastus medialis and vastus lateralis weights primarily influenced the waveform. Key findings include higher vastus medialis weight in the APTA group during P1 and P2, and higher semitendinosus weight in P3 and P4. Additionally, the gastrocnemius and biceps femoris showed significant differences between groups across phases. Conclusions: The APTA group exhibited different muscle synergy patterns under specific phases and load accumulation conditions, particularly in the vastus medialis, medial gastrocnemius, biceps femoris and peroneus longus. The APTA group demonstrated distinct synergy patterns, suggesting a compensatory mechanism to reduce patellar tendon load, potentially increasing knee injury risk. This finding provides new guidance for clinical assessment and intervention strategies for the training and rehabilitation of APTA individuals.