Effects of different blood flow restriction pressure levels on muscular hemodynamics

Abstract

Introduction: Resistance exercise with blood flow restriction (BFR) is an effective method to promote muscle strength gains and hypertrophy. However, little is known about the effects of different BFR levels on hemodynamic responses. Objective: To verify whether the different blood flow restriction pressures applied to the upper limb cause acute changes in vascular microcirculation in young, healthy male adults. Methods: Ten young male visited the laboratory on four occasions. In the first visit, after 10-min rest in supine position, the brachial artery occlusion pressure (AOP) was identified with a Doppler ultrasound. Thereafter, the participants were submitted to a protocol consisting of 1 min for baseline measurements, 2 min of BFR, and 2 min after cuff deflation. It was used a cuff placed on the proximal portion of the forearm and inflated with pressures equivalents to 30% (30BFR), 50% (50BFR) 80% (80BFR), or 100% (100BFR) of the AOP in a random order in separate days. Measurements of tissue saturation index (TSI), oxyhemoglobin, deoxyhemoglobin, and total hemoglobin were collected continuously using near-infrared spectrometry. Results: A two-way ANOVA with repeated measures demonstrated: 1) a significant decrease in TSI in all conditions, with higher decay in 100BFR; 2) a significant increase in oxyhemoglobin in all conditions, but 100BFR; 3) a similar increase in deoxyhemoglobin in all conditions; 4) a significant increase in total hemoglobin in all conditions, mainly in both 30BFR and 50BFR. Conclusion: The relative pressures adopted demonstrated that the hemodynamic changes do not occur linearly with the pressure level imposed by the inflated cuff.