Eccentric muscle damage in elbow flexors: Free weights vs isokinetic dynamometer in trained men

Eccentric exercise-induced muscle damage (EIMD) is commonly assessed using isokinetic dynamometer in research; however, their limited accessibility necessitates exploration of alternative resistance modalities, such as free weights. This study compared the magnitude and time course of EIMD in the elbow flexors following eccentric exercises using either free weights or an isokinetic dynamometer in trained men. Seventeen resistance-trained males (>3 years experience) were randomly assigned to free weights (n = 8) or isokinetic dynamometer (n = 9) groups and performed four sets of 10 maximal eccentric contractions. EIMD was assessed using maximal voluntary isometric contraction (MVIC), delayed-onset muscle soreness (DOMS), muscle thickness, and echo intensity at baseline, immediately postexercise, and across 96 h of recovery. Significant time effects were observed for MVIC (−37% immediately post, −18% at 96 h) and DOMS (∼4 cm increase) in both groups (p < 0.001), with no significant group differences or interactions (p > 0.05). Muscle thickness increased transiently (∼12% postexercise; p < 0.001), whereas echo intensity remained unchanged (p > 0.285). Although statistical differences were absent between the modalities, the magnitude of functional decline (−20–50% MVIC) and DOMS increases are practically relevant for coaches and practitioners, as they provide guidance for planning eccentric training and managing recovery. These findings indicate that free weights eccentric training using 140% of concentric 10RM induces muscle damage comparable to that of isokinetic protocols. Free weights thus represents a viable and accessible option for coaches seeking to apply eccentric loading in trained individuals, provided sufficient recovery is ensured.