A muscle producing force while it lengthens — like lowering a weight.
An eccentric contraction is force production by an active muscle while it is lengthening, resisting or controlling an external load rather than moving it. Lowering a weight under control, the braking phase of landing from a jump, or decelerating the leg during running gait are all eccentric actions. It sits alongside concentric (shortening) and isometric (static-length) contractions as one of the three basic ways muscle generates tension.
Eccentric loading underpins most evidence-based tendinopathy programmes (Achilles, patellar) because it drives tendon adaptation and can improve pain and function even in chronic presentations. It's also relevant when explaining post-exercise soreness to patients, and when programming return-to-sport work, since eccentric strength deficits are linked to hamstring and other strain injuries. Choosing eccentric-biased exercise is therefore a deliberate decision about both tendon/muscle adaptation and injury-risk management, not just a strength-training variant.
Clinically it's applied through exercises like the Alfredson heel drop, slow eccentric squats or Nordic hamstring curls, typically dosed with slow tempo, controlled range, and progressive load or speed over weeks. Eccentric strength can be assessed via controlled lowering tasks, isokinetic dynamometry where available, or simply observing quality of control during functional movements like step-downs or landings. Programme dosage (sets, reps, load, frequency) follows established protocols for the tissue and condition being treated rather than being standardised across all uses.
Eccentric exercise produces more muscle damage, delayed-onset soreness and short-term strength loss than concentric or isometric work, so early sessions can temporarily worsen symptoms or reduce compliance if not explained in advance. It should be introduced gradually, especially in deconditioned or pain-sensitive patients, and isn't automatically superior to other contraction types for every tendinopathy or strengthening goal — the evidence base is strongest for specific tendon conditions rather than as a blanket rule.
This guide was auto-drafted and is pending editorial review.