Slow eccentric- versus concentric-focused resistance training in middle-aged and older women with knee osteoarthritis: A randomized trial

Objective This randomized trial compared the short-term effects of slow eccentric-only resistance training (SET) and slow concentric-only resistance training (SCT), organized within a myofascial chain-based exercise framework, on pain, physical function, muscle strength, muscle mass, and joint range of motion in middle-aged and older women with knee osteoarthritis (KOA). Methods In this randomized, assessor-blinded trial, 56 women with symptomatic KOA were assigned to SET ( n = 28) or SCT ( n = 28) at a university rehabilitation center. Both groups completed a 12-week supervised resistance-training program (2 sessions/week). Outcomes were assessed at baseline and post-intervention using the WOMAC index, muscle strength testing, body composition analysis, functional performance tests, and joint range-of-motion measurements. The trial was registered retrospectively (UMIN-CTR, UMIN000060649, 2026/02/11). Results After 12 weeks, both SET and SCT showed significant within-group improvements in WOMAC pain and physical function, muscle strength, knee extensor torque, fat-free mass, lower-limb muscle mass, and selected functional performance measures (all p < 0.05). No significant between-group differences were detected for any outcome. The observed improvements primarily reflect within-group changes over time, and the results should not be interpreted as formal evidence of equivalence between the two training modes. Conclusion Both SET and SCT were associated with within-group improvements in pain, physical function, muscle strength, and muscle mass over 12 weeks in middle-aged and older women with KOA, with no significant between-group differences. These findings suggest that both approaches are feasible short-term supervised resistance-training options in this population. Additional strategies targeting cardiorespiratory endurance and joint range of motion may be needed within a multimodal rehabilitation program. Trial registration University hospital Medical Information Network Clinical Trials Registry (UMINCTR), UMIN000060649, retrospectively registered on 11/02/2026.