Author(s): KE, S., XIAO, J., Institution: BEIJING INSTITUTE OF SPORTS SCIENCE, Country: CHINA, Abstract-ID: 1042

INTRODUCTION:
Isokinetic and functional movement tests only reflect the external manifestations of knee joint function, and are difficult to identify internal muscle activity. This study combined isokinetic, kinematic tests of functional movements and sEMG tests to investigate the characteristics of myoelectric activity in athletes during knee strength movements and functional movements, so as to provide a reference for sports injury prevention and rehabilitation program formulation.
METHODS:
27 elite judo and rugby athletes were enrolled as subjects, including 13 in the healthy group and 14 with knee joint injuries within two years. All subjects completed knee joint isokinetic tests (60°/s, 180°/s) (ISOmed2000), double-leg isometric squats, single-leg squats(SLS) and single-leg drop landings(SLDL). sEMG (RMS, Co-activation Ratio) of major lower limb muscles (Cometa Wave plus) and kinematic indicators such as dynamic knee valgus angle (DKVA) were collected synchronously. Independent-samples t-test was used between the healthy group and the injured group, and paired t-test was used between the uninjured side and the injured side of the injured group. Spearman rank correlation analysis was performed between myoelectric indicators and knee valgus angle, with the significance level set at P < 0.05.
RESULTS:
The overall sEMG amplitude of the injured group was higher than that of the healthy group, especially in unstable movements such as SLDL, with greater variability in individual activation patterns. Athletes in the injured group showed activation inhibition of the vastus medialis on the injured side. The Co-activation Ratio of vastus medialis to vastus lateralis on the injured side was significantly lower than that on the uninjured side during SLDL and high-speed isokinetic tests, while the RMS of the hamstrings was relatively high. Under muscle fatigue, the increase rate of RMS on the injured side was higher than that on the uninjured side. Some subjects showed muscle deactivation in the middle and late stages of isokinetic knee extension. SLDL was more sensitive to dynamic stability deficits: the DKVA on the injured side of the injured group was significantly larger than that on the uninjured side, while there was no significant difference in SLS. There was no significant correlation between the Co-activation Ratio of vastus medialis to vastus lateralis and DKVA.
CONCLUSION:
Athletes in the knee rehabilitation period present characteristic neuromuscular control abnormalities, with activation inhibition of the vastus medialis on the injured side as the core problem, which is more prominent in dynamic and high-speed movements. The SLDL test is more suitable for screening the risk of dynamic knee instability than the SLS test. This study provides empirical evidence for the formulation of individualized physical training and rehabilitation programs.