RESUMO
BACKGROUND: Limb circumference predicts the pressure needed for complete occlusion. However, that relationship is inconsistent at moderate pressures typical of effective blood flow restriction (BFR) training. The purpose of this study was to investigate the influence of subject factors on BFR at low restriction pressures in the arm. METHODS: Fifty subjects had arm anthropometrics assessed by peripheral quantitative computed tomography (pQCT), sum of skinfold thickness (sumSKF) and Gulick tape (Gulick tape circumference [Gulick Circ.]) at cuff level. Blood flow (BF) was measured with ultrasound at baseline and five restrictive pressures (20, 30, 40, 50 and 60 mmHg). Relationships between subject characteristics and BFR were assessed using Pearson's correlations and hierarchical regression. RESULTS: BF decreased (p < 0.05) at each incremental pressure. Regression models including percent muscle composition (%Muscle), pQCT circumference and systolic blood pressure (SBP), were significant at all five pressures (R2 = 0.18-0.49). %Muscle explained the most variance at each pressure. Regression models including sumSKF, Gulick Circ. and SBP, were significant at 30-60 mmHg (R2 = 0.28-0.49). SumSKF explained the most variance at each pressure. CONCLUSIONS: At low pressures (20-60 mmHg), there is considerable variability in the magnitude of BFR across individuals. Arm composition factors (muscle and fat) explained the greatest variance at each cuff pressure and may be the most important consideration when using BFR protocols.