(9) EVALUATION OF NEUROMUSCULAR FUNCTION USING NONLINEAR ANALYSIS BETWEEN INDIVIDUALS WITH PATELLAR TENDINOPATHY AND UNINJURED INDIVIDUALS

Purpose: The purpose of this study was to evaluate traditional and nonlinear measures of neuromuscular function between individuals with patellar tendinopathy and uninjured controls. Methods: 40 female Division I athletes (19.5 ± 1.4 years, BMI: 23.0 ± 2.8 kg/m²) underwent isokinetic quadriceps strength testing. The individuals completed 5 maximal effort repetitions at isokinetic speeds of 60°/s and 180°/s for both legs. Work per repetition and average power per repetition were extracted during both flexion and extension. Sample entropy (SampEn) of the torque signal was calculated with the template length (m) set at 2 and the tolerance for accepting matches (r) set at 0.2. Normality of the data was assessed with a Shapiro-Wilk test and homogeneity was assessed with an F-test. Data sets that met the assumptions of normal distribution and equal variance were compared using t-tests (α=0.05), and Cohen’s d effect sizes were calculated. Data sets violating normality or equal variance assumptions were evaluated using Mann-Whitney tests, and effect sizes were calculated. Results: There were no significant differences in work per repetition between limbs with patellar tendinopathy and uninjured limbs for both flexion and extension at 60°/s and 180°/s (Table 1). There were no significant differences in average power per repetition between limbs with patellar tendinopathy and uninjured control limbs for both flexion and extension at 60°/s and 180°/s. There were significantly higher sample entropy values of the isokinetic torque signals in the limbs with patellar tendinopathy compared to uninjured control limbs for the flexion 60°/s condition. There were no significant differences in SampEn between limbs with patellar tendinopathy and uninjured control limbs for the extension 60°/s, extension 180°/s, and flexion 180°/s condition. Conclusions: There were no significant differences between limbs with patellar tendinopathy and uninjured control limbs for work per repetition and average power per repetition. There was a significant difference in SampEn between limbs with patellar tendinopathy and uninjured control limbs during the flexion 60°/s condition. These results suggest that limbs with patellar tendinopathy may exhibit similar strength and power metrics compared with healthy controls but exhibit less neuromuscular control during tasks involving slow speed flexion strength at the knee. These results further suggest that nonlinear analyses may provide additional information regarding neuromuscular function that traditional measures do not capture. Practical Applications: This study contributes to the notion that slow, heavy resistance training that incorporates principles of neuromuscular control and tendon load tolerance may benefit individuals with patellar tendinopathy. Specifically, protocols that progressively load the tendon, such as tempo squats or slow step downs, may mitigate pain and aid tendon healing. Acknowledgements: None