Sample entropy detects altered neuromuscular control in female athletes with patellar tendinopathy

Traditional measures of neuromuscular function, such as maximal voluntary isometric contraction strength and hamstring to quadriceps torque ratio, allow for comparison of peak strength between limbs with patellar tendinopathy and limbs without. However, nonlinear analyses evaluate the evolution of a torque signal over time and, therefore, may provide new insights regarding neuromuscular function. The purpose of this study was to determine differences in neuromuscular function between individuals with and without patellar tendinopathy using traditional and nonlinear measures.

Twelve female Division 1 athletes (19.7 ± 1.6 years, BMI: 24.5 ± 2.1 kg/m²) with patellar tendinopathy and twenty-eight female Division 1 athletes without patellar tendinopathy (19.4 ± 1.3 years, BMI: 22.4 ± 2.8 kg/m²) performed isokinetic strength assessments for knee extension and flexion. Maximum torque, maximum work per repetition, average power per repetition, and sample entropy were calculated from the isokinetic strength assessments.

Sample entropy was significantly greater in limbs with patellar tendinopathy compared to healthy control limbs during flexion at 60°/s. There were no significant group differences for other results.

Individuals 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. Furthermore, nonlinear analyses may provide additional information regarding neuromuscular function that traditional measures do not capture.