No abstract

This study developed a method to detect knee wobbling (KW) at low knee flexion. KW consists of quick uncontrollable medio-lateral knee movements without knee flexion, which may indicate a risk of ACL injury. Ten female athletes were recorded while performing slow, single-leg squats. Using motion capture data, the ratio of the frontal angular velocity to sagittal angular velocity (F/S) was calculated. An ‘F/S spike’ was defined when the F/S ratio exceeded 100%. The number of F/S spikes was counted before and after low-pass filtering at different cut-off frequencies. Intraclass correlation coefficients for KW and filtered F/S spike were analysed. KWs per squat cycle showed a median (range) of 3 (2–8) times. F/S spikes before and after low-pass filtering at 3-, 6-, 10-, and 15-Hz were 51 (12–108), 2 (0–6), 3 (1–12), 5 (2–21), and 9 (3–33) times, respectively. KWs and F/S spikes on motion capture with 6-Hz, low-pass filtering were well correlated ( r = 0 .76). Median percentages of valgus and varus F/S spikes were 71% and 29%, respectively. After 6Hz, low-pass filtering, the number of F/S spikes was strongly correlated with observed KWs. An F/S spike assessment may be used to objectively detect KW, including flexion and varus/valgus angular velocity.

The accuracy and precision of synchronization and phase coherence values have been used as evaluation measures of retraction. However, it has been pointed out that accuracy and precision of synchronization may show a discrepancy between neural entrainment and performance accuracy. Therefore, this study determined whether the phenomenon of motor retraction to auditory stimuli can be evaluated by using phase synchronization with tapping. For this purpose, we examined phase coherence values, surrogate data methods, and effect sizes from a mathematical perspective. The auditory stimulus interval at which retraction is most likely to occur was also identified. Specifically, tapping tasks at six tempi (400, 500, 600, 750, 1,000, and 2,000 ms) were performed on 20 young adults. A comparison of the data for each auditory stimulus condition revealed significant differences at 400, 500, 600, 750, and 1,000 ms. Moreover, the effect size was greatest at 400 ms. The results suggest that, among the five conditions in which retraction occurred, the 400 ms auditory stimulus interval had the lowest probability of being an error in retraction determination and was therefore deemed suitable for evaluation.

Objectives: This study was aimed to reveal the differences in knee valgus angle at landing as a static indicator and wobbling movement of the knee during landing as a dynamic indicator between ACL injury and uninjured athletes. Methods: This study was case-control study. There were 6 female basketball players with ACL injuries and 38 female basketball players without them, whose knee kinematics were measured using 2-dimensional video cameras during single-leg jump landings. The task was performed from 30cm-box. Knee kinematics and wobbling of the knee which was calculated by relative frontal motion to the flexion movement were compared between knees with ACL-injured and uninjured. Results: Six athletes who had confirmed ACL injuries, did not demonstrate significantly different knee valgus angle at initial contact and maximum knee flexion during landing, compared to 38 uninjured athletes. The knee valgus angles at initial contact for injured and uninjured athletes were 12.3° and 14.8° (p = 0.15), respectively. Five of six anterior cruciate ligament injured knees presented knee wobbling during landing. Relative frontal motion at 18° knee flexion was significantly greater in athletes with ACL-injured (p = 0.02). Conclusions: 84% of ACL injury presented with the knee wobbling and the frontal knee motion was greater with low knee flexion during knee wobbling, while the knee valgus angle was not significantly different. This study suggests that knee wobbling may be a biomechanical and dynamic risk factor for ACL injury in female basketball players.