Firminger, Colin R.Edwards, W. Brent2024-05-232024-05-232021Firminger, C. R., & Edwards, W. B. (2021). Effects of cyclic loading on the mechanical properties and failure of human patellar tendon. Journal of Biomechanics, 120, 110345. https://doi.org/10.1016/j.jbiomech.2021.1103450021-9290https://hdl.handle.net/1880/118824https://doi.org/10.11575/PRISM/46421Patellar tendinopathy is a common overuse injury in sports such as volleyball, basketball, and long-distance running. Microdamage accumulation, in response to repetitive loading of the tendon, plays an important role in the pathophysiology of patellar tendinopathy. This damage presents mechanically as a reduction in Young’s modulus and an increase in residual strain. In this study, 19 human patellar tendon samples underwent cyclic testing in load control until failure, segmented by four ramped tests where digital image correlation (DIC) was used to assess anterior surface strain distributions. Ramped tests were performed prior to cyclic testing and at timepoints corresponding to 10%, 20%, and 30% of cyclic stiffness reduction. Young’s modulus significantly decreased and cyclic energy dissipation significantly increased over the course of cyclic testing. The DIC analysis illustrated a heterogeneous strain distribution, with strain concentrations increasing in magnitude and size over the course of cyclic testing. Peak stress and initial peak strain magnitudes significantly correlated with the number of cycles to failure (r2 = 0.65 and r2 = 0.57, respectively, p < 0.001); however, the rates of peak cyclic strain and modulus loss displayed the highest correlations with the number of cycles to failure (r2 = 96% and r2 = 86%, respectively, p < 0.001). The high correlation between the rates of peak cyclic strain and modulus loss suggest that non-invasive methods to continuously monitor tendon strain may provide meaningful predictions of overuse injury in the patellar tendon.enUnless otherwise indicated, this material is protected by copyright and has been made available with authorization from the copyright owner. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.Attribution-NonCommercial-NoDerivatives 4.0 InternationalFatigue loadingTendinopathyDigital image correlationTendon mechanicsSurface strain distributionsArticlehttps://doi.org/10.1016/j.jbiomech.2021.110345