In Achilles Tendinopathy the Symptomatic Tendon Differs from the Asymptomatic Tendon While Exercise Therapy Has Little Effect on Asymmetries-An Ancillary Analysis of Data from a Controlled Clinical Trial.

BACKGROUND

As inter-limb asymmetries can be associated with higher injury risk, we aimed to investigate their role in Achilles tendinopathy patients.

METHODS

In Achilles tendinopathy patients (n = 41), we assessed inter-limb asymmetries of mechanical, material, and morphological musculoskeletal properties and function and how those were affected by 12 weeks of exercise intervention (high-load protocol, n = 13; Alfredson protocol, n = 11). Moreover, we assessed whether asymmetry reductions correlated with improved Patient-Reported Outcomes (VISA-A score).

RESULTS

At baseline, tendinopathic tendons demonstrated lower tendon force ( = 0.017), lower tendon stress ( < 0.0001), larger tendon cross-sectional area (CSA) ( < 0.001), and increased intratendinous ( = 0.042) and tendon overall ( = 0.021) vascularization. For the high-load group, PRE-to-POST asymmetry comparisons revealed an asymmetry increase for the counter-movement jump (CMJ) ( = 0.034) and PRE-to-POST VISA-A score improvements correlated with CSA asymmetry reductions ( = 0.024). Within the Alfredson group, PRE-to-POST VISA-A score improvements correlated with CMJ asymmetry reductions ( = 0.044) and tendon stiffness asymmetry increases ( = 0.037). POST-to-POST in-between group comparisons revealed lower asymmetry in the high-load group for tendon elongation ( = 0.021) and tendon strain ( = 0.026).

CONCLUSIONS

The tendinopathic limb differs from the asymptomatic limb while therapeutic exercise interventions have little effect on asymmetries. Asymmetry reductions are not necessarily associated with tendon health improvements.