No short-term changes in tendon structure following temporary replacement of running with low-impact exercises in service members with midportion Achilles tendinopathy: a prospective cohort study.

Abstract

Introduction: Midportion Achilles tendinopathy (mid-AT) is associated with tendon degeneration that may worsen due to mechanical loading. Contrastingly, load can also improve tendon structure. We aimed to evaluate short-term changes in midportion tendon structure and their associations with symptoms, following temporary replacement of running with low-impact exercises on a stair climber or cross-trainer, in service members with mid-AT.

Methods: We recruited 40 service members (40 symptomatic tendons) for this study. Ultrasound tissue characterisation (UTC) was used to quantify aligned fibrillar structure (echo-type I+II) and disorganised structure (echo-type III+IV), in the tendon midportion (2-7 cm) and in the area of maximum degeneration (AoMD) within the midportion. Symptoms were evaluated with the modified Victorian Institute of Sports Assessment - Achilles (VISA-A) questionnaire. All measurements were performed at baseline and after 8 weeks. The Wilcoxon signed-rank test was used to evaluate differences in UTC and VISA-A. Spearman's rho was used to calculate the correlations between UTC and VISA-A change scores.

Results: Tendon structure did neither change significantly in the midportion: echo-type I+II from median 64.7% (IQR 19.4) to 68.6% (IQR 25.1) (p=0.793); echo-type III+IV from median 35.3% (IQR 19.4) to 31.5% (IQR 25.1) (p=0.775) nor in the AoMD: echo-type I+II from median 56.3% (IQR 18.0) to 57.9% (IQR 32.0) (p=0.677); echo-type III+IV from median 43.8% (IQR 18.0) to 42.3% (IQR 32.1) (p=0.572).On the other hand, VISA-A improved significantly (p=0.000) from baseline (median 46.5, IQR 16.0) to follow-up (median 56.0, IQR 9.0). Correlations between UTC and VISA-A change scores were consistently graded as low (range: 0.309-0.338).

Conclusions: Although the replacement of running with low-impact exercises improved symptoms, no changes in tendon structure were observed after 8 weeks. Changes in midportion structure and symptoms were poorly associated. These findings can support loading advice in patients with mid-AT when aiming to prevent progressive degeneration or tendon rupture.

Trial registration number: NL69527.028.19, "Centrale Commissie Mensgebonden Onderzoek" (CCMO).