Ultrasound-based evaluation of changes in tendon macro- and micromorphology following exercise and ESWT in mid-portion Achilles tendinopathy: A randomized clinical trial with a 26-week follow-up.

OBJECTIVES

To evaluate effects of progressive resistance training alone and in combination with focused extracorporeal shockwave therapy on tendon macromorphology measured by ultrasound and micromorphology evaluated using spatial frequency analysis in chronic midportion Achilles tendinopathy.

DESIGN

Prospective single-center randomized clinical trial.

METHODS

41 participants with unilateral chronic midportion Achilles tendinopathy were randomized to resistance training alone or resistance training combined with focused extracorporeal shockwave therapy. Both groups performed a 12-week progressive loading program. The combined group additionally received four focused extracorporeal shockwave therapy sessions. Examinations were performed at baseline, weeks 6, 12, and 26 to assess tendon diameter, cross-sectional area, and micromorphological parameters (PSFR, P6, Q6, PPP, SUM). Pain (numeric rating scale) and function (Victorian Institute of Sports Assessment - Achilles questionnaire) were evaluated concurrently. Contralateral asymptomatic tendons served as reference values.

RESULTS

Both groups showed significant pain reduction and functional improvement (p < 0.001). Macromorphological parameters changed minimally. Cross-sectional area decreased significantly only at week 26 in the combined group (p = 0.031). Spatial frequency analysis revealed time-dependent micromorphological remodeling with decreased P6 and SUM and increased PPP and Q6, consistent with improved collagen organization and tissue homogeneity. This remodeling pattern appeared more pronounced in the combined group.

CONCLUSIONS

Progressive resistance training, either alone or combined with focused extracorporeal shockwave therapy, leads to clinically meaningful improvements in chronic midportion Achilles tendinopathy. The addition of focused extracorporeal shockwave therapy may accelerate and amplify intratendinous micromorphological reorganization, supporting its role as a physiological catalyst for tendon remodeling rather than solely a symptom-modulating adjunct.