Tendon morphological and mechanical responses to eccentric and heavy-slow resistance training in Achilles and patellar tendinopathy: a scoping review

Tendinopathy is a disabling and painful condition commonly associated with repetitive mechanical loading. Eccentric training (ECC) has been widely used in rehabilitation but can be mechanically demanding and pain-provoking. Heavy-Slow Resistance Training (HSRT) has emerged as an alternative loading strategy for treatment of tendinopathies. This study aims to investigate the changes of chronic eccentric training (ECC) and HSRT on morphological, mechanical, and clinical outcomes in patients with patellar and Achilles tendinopathy. An electronic search was conducted in Pubmed, Scopus, and Web of Science in January 2024, with updated in January 2025 and April 2026. In total, 7176 studies were identified. After removing duplicates ( n = 2543) the remaining articles were screened by two researchers by title and, if necessary, by abstract or full text to check eligibility. Studies investigating adults with Achilles or patellar tendinopathy who underwent ECC or HSRT were eligible. The outcomes assessed were tendon thickness, stiffness, cross-sectional area, neovascularization and young’s modulus, along with pain, muscle strength, and the Victorian Institute of Sports Assessment (VISA) questionnaire. After a thorough screening process, 16 studies were included in the review. Both interventions showed beneficial results on clinical and functional outcomes, increasing muscle strength and VISA questionnaire score on both tendons, and decreasing pain. Descriptively, the reduction in neovascularization was larger following HSRT than ECC (-23.2% vs. -11.7%), while the increase in tendon stiffness was larger following ECC (7.1% vs. 0.3%). Our results are in line with the available literature on the improvement in clinical outcomes, including pain and function, alongside adaptations in tendon morphological and mechanical properties. HSRT may represent an alternative loading strategy to ECC in the rehabilitation of Achilles and patellar tendinopathy; however, the limited number of direct comparisons and heterogeneity across intervention protocols preclude conclusions regarding the superiority of either approach.