Eccentric Training for Tendons: What the Evidence Actually Supports

Eccentric exercise — slow, controlled lengthening contractions like the heel drop for Achilles tendinopathy or the slow lowering phase of a leg extension for patellar tendon issues — has been a staple of tendon rehabilitation for over two decades. Two recent reviews help clarify what this approach actually delivers, and where the evidence is thinner than the popularity of the method suggests.

What a 2025 scoping review found

A scoping review and evidence gap map published in 2025 analyzed 31 studies on eccentric training for tendinopathy specifically in athletes, covering conditions like patellar tendinopathy in jumping-sport athletes and Achilles tendinopathy in runners. The consistent finding across this body of work: eccentric training reliably reduces pain and improves function in athletes with tendinopathy, and it does so safely. Return-to-sport rates were generally favorable.

Where the evidence runs thin

The same review was candid about its limits. Eccentric training protocols varied widely in load, frequency, and progression across studies, making direct comparisons difficult. Reporting on return-to-sport timelines, on-field performance, and actual tendon structural changes was inconsistent. Study samples skewed heavily male, and long-term follow-up and adverse event tracking were both sparse. Evidence for some tendinopathies, like proximal hamstring issues, was particularly thin. The reviewers suggested that higher-load resistance strategies may enhance outcomes further, but standardized protocols are still needed.

What the research says about how eccentric training works

A separate review focused on the underlying tendon adaptations found a more nuanced picture than "eccentric is special." Tendons respond to mechanical loading in general by increasing stiffness and elastic modulus, and comparisons between eccentric and concentric training on tendon adaptation were, in the reviewers' words, "somewhat conflicting" — in young, healthy people there appears to be no clear difference between contraction types for overall tendon adaptation. Some studies of high-intensity eccentric loading on the Achilles tendon showed increased stiffness, while lower-load protocols like the classic Alfredson heel-drop program showed no change or even decreased stiffness, suggesting a loading threshold has to be crossed before adaptation occurs.

Why eccentric training still matters, especially for older adults

If eccentric loading isn't uniquely superior for tendon adaptation in young athletes, why does it remain a first-line rehabilitation tool? The practical answer lies in its mechanical properties: eccentric contractions require less metabolic energy and produce lower perceived exertion than concentric contractions at a comparable mechanical load, which allows heavier loading of the tendon without the cardiovascular and metabolic strain of equivalent concentric work. This is particularly valuable for older adults, whose tendons stiffen and lose elasticity with age and who may have compromised mitochondrial function that limits how much concentric exercise they can tolerate.

Practical takeaway

Eccentric training remains a safe, effective, evidence-backed tool for managing tendinopathy in athletes, and its low metabolic cost makes it especially well-suited to older or deconditioned populations. What the evidence doesn't yet support is the idea that eccentric loading has some unique biological advantage over well-dosed concentric or heavy slow resistance training — the loading dose and progression likely matter more than the specific contraction type. For athletes and coaches, the practical priority should be consistent, adequately loaded tendon rehabilitation rather than rigid adherence to eccentric-only protocols.