Stiffness of elastic cuffs affects physiological and perceptual responses but not motor performance fatigue during low external load resistance exercise with practical blood flow restriction

Practical blood flow restriction (pBFR), using non-pneumatic elastic cuffs, is a feasible and cost-effective alternative to pneumatic systems. There is evidence that cuff stiffness influences haemodynamic and perceptual responses in the upper body during rest. However, the impact of cuff stiffness during exercise is still unknown. Therefore, this study investigated the influence of cuff stiffness on physiological, perceptual, and performance changes during exercise. In a randomized and counterbalanced order, ten recreationally active males performed four sets of unilateral elbow flexions at 20% of individuals' one-repetition-maximum with two elastic cuffs of different stiffness (low stiffness cuff [LS] and high stiffness cuff [HS]) each applied with two different overlaps (10% and 20% overlap in relation to the limb circumference) as well as a control condition without pBFR. Before and after exercise, maximal voluntary isometric contraction torque was measured to assess motor performance fatigue. During exercise, muscle oxygen saturation of the biceps brachii as well as effort and exercise-induced muscle pain perception were recorded. Statistical analysis revealed that motor performance fatigue was not different between conditions (BF₁₀ = 0.289). The decline in muscle oxygen saturation (BF₁₀ = 8.508 and BF₁₀ = 1039.543) as well as effort (BF₁₀ = 2646.104 and BF₁₀ = 2.773∙10⁶) and exercise-induced muscle pain perception (BF₁₀ = 14087.983 and BF₁₀ = 7.306∙10⁹) were higher when using the stiffer cuff at 10% and 20% overlap, respectively. Conclusively, physiological and perceptual responses but not motor performance fatigue were affected by cuff stiffness when equal relative overlaps were applied.