Proximal, Distal, and Contralateral Effects of Blood Flow Restriction Training on the Lower Extremities: A Randomized Controlled Trial

Background: Blood flow restriction (BFR) training involves low-weight exercises performed under vascular occlusion via an inflatable cuff. For patients who cannot tolerate high-load exercises, BFR training reportedly provides the benefits of high-load regimens, with the advantage of less tissue and joint stress. Hypothesis: Low-load BFR training is safe and efficacious for strengthening muscle groups proximal, distal, and contralateral to tourniquet placement in the lower extremities. Study Design: Randomized controlled trial. Level of Evidence: Level 1. Methods: This was a randomized controlled trial of healthy participants completing a standardized 6-week course of BFR training. Patients were randomized to BFR training on 1 extremity or to a control group. Patients were excluded for cardiac, pulmonary, or hematologic disease; pregnancy; or previous surgery in the extremity. Data collected at baseline and completion included limb circumferences and strength testing. Results: The protocol was completed by 26 patients, providing 16 BFR and 10 control patients (mean patient age, 27 years; 62% female). A statistically greater increase in strength was seen proximal and distal to the BFR tourniquet when compared with both the nontourniquet extremity and the control group (P \u3c 0.05). Approximately twice the improvement was seen in the BFR group compared with controls. Isokinetic testing showed greater increases in knee extension peak torque (3% vs 11%), total work (6% vs 15%), and average power (4% vs 12%) for the BFR group (P \u3c 0.04). Limb circumference significantly increased in both the thigh (0.8% vs 3.5%) and the leg (0.4% vs 2.8%) compared with the control group (P \u3c 0.01). Additionally, a significant increase occurred in thigh girth (0.8% vs 2.3%) and knee extension strength (3% vs 8%) in the nontourniquet BFR extremity compared with the control group (P \u3c 0.05). There were no reported adverse events. Conclusion: Low-load BFR training led to a greater increase in muscle strength and limb circumference. BFR training had similar strengthening effects on both proximal and distal muscle groups. Gains in the contralateral extremity may corroborate a systemic or crossover effect. Clinical Relevance: BFR training strengthens muscle groups proximal, distal, and contralateral to cuff placement. Patients undergoing therapy for various orthopaedic conditions may benefit from low-load BFR training with the advantage of less tissue stress