Abstract

Background: While exercise is a key part of knee osteoarthritis (OA) management, the optimal dose for acute pain relief remains unclear. We aimed to determine the optimal resistance exercise volume to induce exercise-induced hypoalgesia (EIH) in older adults with severe knee OA. Methods: 28 participants (11/17 women/men; mean age = 71.6 ± 5.2 years) with severe knee OA awaiting unilateral Total Knee Arthroplasty were recruited. They were randomised to four experimental conditions (cross-over design) conducted with a separation of 4 days. Knee extension exercises with elastic resistance were performed at single exercise sessions at 10 repetition maximum (RM) intensity, while varying the number of sets (control with no exercise, 4 sets, 8 sets, and 12 sets). Results: Higher exercise volumes (12 and 8 sets) induced greater EIH 10 min post-exercise compared to lower volumes (4 sets) or no exercise, with significant differences favouring the 12-set exercise intervention (η2 = 0.472, p < 0.001). Pain intensity increased immediately post-exercise in all exercise interventions but returned to baseline after 10 min in the 4- and 12-set exercise interventions. PPT increased post-10 min in the 8- and 12-set exercise interventions for both the affected and contralateral limbs (p < 0.05). PCS moderated the EIH response, reducing its effect in the 12-set (r = −0.436, p < 0.05) and 8-set (r = −0.418, p < 0.05) exercise intervention. Conclusions: Greater resistance exercise volume appears to be associated with an initial increase in pain perception followed by a delayed hypoalgesic response in patients with severe knee OA. These exploratory findings suggest that higher-volume resistance exercise may be a valuable strategy for acute pain relief, although clinicians should balance short-term discomfort with long-term benefits, considering both physical and psychosocial factors, to improve pain-related outcomes aimed at reducing acute pain in this population. However, further research is needed to confirm these effects beyond a controlled, single-exercise acute intervention. © 2025 The Authors