Effects of an isokinetic knee extension maximum effort task on patellar tendon properties: An ultrasound B-mode and...

Acute alterations on patellar tendon properties following an isokinetic knee extension task with a fatigue protocol remains unknown. To investigate this, nineteen (11♂, 8♀) physically active individuals participated in this study. Patellar tendon was assessed using ultrasonography in B-mode and shear wave elastography modes with the knee at 30° of flexion (0° = full extension). Tendon and subcutaneous fat tissue thickness, and echo intensity (EI) were analyzed from the extended field of view B-mode images. Mean shear wave velocity (SWV) was analyzed from the SWE images. This process was performed before and immediately after the isokinetic task, which included a fatigue protocol. Mechanical work was calculated for the first and last five repetitions to assess performance fatigability. Pre-post comparisons were performed using paired t-tests, and correlations between tendon EI and SWV were assessed using Pearson's correlation. Reliability was evaluated using the intraclass correlation coefficient (ICC), standard error of measurement (SEM) and minimum detectable change (MDC). Statistical significance was set at α = 0.05, and Cohen's d was calculated for effect size. While no differences in tendon thickness were observed (p = 0.208), EI increased 9% (p < 0.001, ES = 0.73) and SWV decreased 5% (p = 0.031, ES = 0.23) after the isokinetic task. Although EI and SWV correlated before the isokinetic task (r = 0.468, p = 0.043), no correlations were observed after it (r = 0.279, p = 0.247) and between EI and SWV variation (r = -0.419, p = 0.074). Very high reliability was seen before and after the isokinetic task (ICC ≥ 0.922, p < 0.001). However, SWV mean difference pre-post task was lower than MDC.