Achilles Tendon Tangent Moduls of Runners

The present work seeks to provide a reliable estimation of Achilles tendon (AT) mechanical properties, especially the maximum tangent modulus (ET max) and its relationship with respect to deformation, comparing long-distance runners and pentathletes. Six pentathletes and six long-distance runners (different weekly running training volume than pentathletes (116.7 ± 13.7 vs. 58.3 ± 20.4 km, p < 0.01)). From the analysis of ET curves, it can be observed that the long-distance runners’ group presented higher ET max (380. 6 ± 92.22 vs. 36.2 ± 82.6 MPa, p < 0.05) and maximum true stress than pentathletes (24.2 ± 5.1 vs. 16.0 ± 3.5 MPa, p < 0.05). The higher AT ET max of long-distance runners suggests a higher material stiffness in the group that trains the highest weekly run volume, as well as higher AT elastic energy storage capacity. This approach can be used as a tool for evaluation and monitoring of high-performance running athletes.