Achilles tendon material properties are greater in the jump leg of jumping athletes

Abstract

Purpose: The Achilles tendon (AT) must adapt to meet changes in demands. This study explored AT adaptation by comparing properties within the jump and non-jump legs of jumping athletes. Non-jumping control athletes were included to control limb dominance effects. Methods: AT properties were assessed in the preferred (jump) and non-preferred (lead) jumping legs of male collegiate-level long and/or high jump (jumpers; n=10) and cross-country (controls; n=10) athletes. Cross-sectional area (CSA), elongation, and force during isometric contractions were used to estimate the morphological, mechanical and material properties of the ATs bilaterally. Results: Jumpers exposed their ATs to more force and stress than controls (all p≤0.03). AT force and stress were also greater in the jump leg of both jumpers and controls than in the lead leg (all p<0.05). Jumpers had 17.8% greater AT stiffness and 24.4% greater Young’s modulus in their jump leg compared to lead leg (all p<0.05). There were no jump versus lead leg differences in AT stiffness or Young’s modulus within controls (all p>0.05). Conclusion: ATs chronically exposed to elevated mechanical loading were found to exhibit greater mechanical (stiffness) and material (Young’s modulus) properties.