Blood Flow Restricted Resistance Exercise Reduces the Performance of Contralateral Homologous Muscles.

To examine whether resistance exercise with blood flow restriction (BFR) impairs performance in the contralateral limb and whether this effect depends on the presence of contraction. 30 individuals (19-31 years) completed three laboratory visits. During two experimental visits, participants performed four randomized experimental conditions. The dominant (tested) arm performed two sets of elbow flexion exercise to failure at 30% 1RM, while the non-dominant arm simultaneously received: 1) no exercise (Non-Ex), 2) exercise at 30% 1RM (Ex), 3) BFR without exercise (BFR-only), and 4) Ex with 80% arterial occlusion pressure (AOP) (Ex+BFR). Sets were terminated only when the dominant arm failed to maintain proper form or prescribed cadence (40 bpm). Participants completed two conditions per visit (20-min rest). A Bayesian repeated-measures ANOVA tested differences in repetitions and exercise-induced discomfort ratings (0-100 AU), and mediation analysis assessed whether discomfort explained performance differences. Repetitions across sets were lower with Ex+BFR [21.7 (7.4)] compared to Non-Ex [25.8 (8.5)], Ex [28.3 (11.7)], and BFR-only [24.7 (8.2)]. BFR-only resulted in fewer repetitions than Ex, but the differences in other conditions were inconclusive. Mean discomfort rating was highest in Ex+BFR [60.3 (25.1)], and BFR-only augmented discomfort ratings [49.2 (24.0)] relative to Non-Ex [41.0 (24.9)] and Ex [42.1 (24.0)]. Mediation analysis indicated that discomfort contributed to the reduction in performance observed in Ex+BFR relative to Non-Ex. The local fatigue enhanced by BFR impaired exercise performance in the non-restricted limb. The sensory feedback mechanisms may play a large role in fatigue development with BFR.