Inter-individual variability in pain perception and sensitivity responses to low-load exercise with an absolute or relative blood flow restriction pressure.

Our aim was to determine whether pain and hypoalgesic responses to low-load resistance exercise with two different (absolute vs. relative) pressure methods of blood flow restriction (LL-BFR) show true inter-individual variability. Eighty-two healthy adults [21 (3) years] completed two randomized cycles of LL-BFR and time-matched seated rest (control). Participants were randomly assigned to perform unilateral knee extension at either absolute pressure (100 mmHg; n = 42) or relative (80% of arterial occlusion pressure; n = 40), with repetitions prescribed as 70% of their maximal repetition capacity. Thigh pain, upper- and lower-body pressure pain threshold (PPT) were measured pre- and post-condition. Across the total sample, LL-BFR increased thigh pain and lower body PPT versus control (4.13 AU and 0.27 kg/cm2), with evidence of significant inter-individual variability [Participant-by-Treatment interaction: 1.24 (1.1, 1.4) AU and 0.23 (0.11, 0.32) kg/cm2]. Responses were consistent across cycles for thigh pain [r = 0.82 (0.75, 0.87)] but not lower body PPT [r = 0.16 (-0.02, 0.33)]. Adding a Treatment-by-Group interaction in the model did not numerically impact the inter-individual variability. Our data suggests that individuals perceive pain from blood flow restricted exercise differently, and the inter-individual variability appears regardless of pressure application method.