Effect of low-intensity resistance training at different levels of blood flow restriction on pain, proprioception and muscle strength in patients with knee osteoarthritis: a randomized controlled trial

Low-intensity resistance training(LIRT) combined with blood flow restriction(BFR) has significant potential for promoting functional recovery in patients with knee osteoarthritis(KOA). However, the optimal level of BFR that works most effectively in combination with LIRT remains unclear. This study seeks to evaluate the effects of LIRT at varying BFR levels on pain, proprioception, and muscle strength in KOA patients. A total of 100 KOA patients were randomly assigned to four groups: LIRT, LIRT + BFR30%, LIRT + BFR50%, and LIRT + BFR80%. The LIRT group received only LIRT, while the LIRT + BFR30%, LIRT + BFR50%, and LIRT + BFR80% groups underwent LIRT with BFR applied at 30%, 50%, and 80% of arterial occlusion pressure(AOP), respectively. Each group underwent 8 weeks of intervention, with assessments performed before and after the intervention. The primary outcome was the Visual Analogue Scale (VAS), and the secondary outcomes were proprioception and muscle strength. In addition, adverse effects, adherence, and tolerance during the intervention were recorded. Two-way repeated measures ANOVA revealed significant group-by-time interaction effects for VAS(P < 0.001,η²p=0.190), absolute error(AE) values of 60° knee flexion(P < 0.001, η²p=0.597); knee extension peak torque(P < 0.001,η²p=0.363), average peak torque(P < 0.001,η²p=0.177), and average power(P = 0.003,η²p=0.138) at 60°/s; peak torque(P = 0.003,η²p=0.140), average peak torque(P = 0.047,η²p=0.081), and average power(P = 0.004,η²p=0.136) at 120°/s. The VAS scores in the LIRT + BFR80% group post-intervention were significantly lower than the LIRT + BFR30% group (P = 0.044) and showed a trend of being lower than the LIRT + BFR50% group (P = 0.058). The LIRT + BFR80% group demonstrated lower AE values of 60 ° knee flexion and higher peak torque, average peak torque, and average power at 60°/s after intervention compared to the LIRT + BFR30% and LIRT + BFR50% groups (P < 0.05). Furthermore, peak torque and average peak torque at 120 °/s in the LIRT + BFR80% group after intervention were higher than those in the LIRT + BFR30% group (P < 0.05). No serious intervention-related adverse effects were reported in either group, and patient adherence and tolerance were satisfactory. BFR at 80% AOP combined with LIRT appears to be the most effective protocol for improving pain, proprioception, and muscle strength in KOA patients, compared to LIRT + BFR30% and LIRT + BFR50%. This study was registered in the Chinese Clinical Trial Register (https//www.chictr.org.cn/) with the registration number ChiCTR2300067778 (Registration date 23/01/2023).