Abby R. Fleming, Lee J. Winchester, Keith S. Saffold. The University of Alabama, Tuscaloosa, AL.

BACKGROUND: Blood Flow Restriction (BFR) during resistance exercise mimics the hypoxic environment that is seen while exercising at high intensities, but during low-intensities. There have been few studies investigating the cardiac and hemodynamic responses to BFR with conflicting results, but there is limited information about blood flow redistribution with BFR at rest. The purpose of this study was to determine the physiological changes that occur during the two most common clinical BFR pressures (50% and 80% of limb occlusion pressure (LOP)), when providing occlusion to the lower limbs. Heart rate (HR), blood pressure (BPsys and BPdia), mean arterial pressure (MAP), tibial and brachial artery blood flow (TBF and BBF), mean velocity (TTAMV and BTAMV), blood vessel area (Tarea and Barea) and diameter (Tdis and Bdis) were analyzed. METHODS: Seven healthy men (age: 25.1±4.6 years; height: 182.2±6.7 cm; body mass: 87.2± 10.9kg, and body fat: 14.8±6.2%) participated in this study. Participants sat on a gurney chair with Delfi PTS cuffs on both thighs. Baseline (T1) measurements of HR, BP, MAP, BF in the brachial and posterior tibial arteries were evaluated after resting for at least 5 minutes. Both cuffs were inflated for 8 minutes, to either 50% or 80% of LOP. HR, BP and MAP was monitored throughout the entire 8 minutes of inflation and 8 minutes of post-occlusion rest using the Finapres NOVA. Brachial and tibial artery measurements were taken at T2 and T3, at least 30 seconds after inflation. After deflation, participants remained seated for 8 minutes with no BFR, all the measurements were re-collected at 0-4 (T4) and 4-8 (T5) minutes post-occlusion. Repeated measures ANOVA with Bonferroni correction was used to determine significant changes. An alpha level of < 0.05 was used to determine significance. RESULTS: There were no significant differences for any measurements in the 50% BFR pressure. During the 80% BFR pressure session, Hr was significantly higher at T2 vs T5 and T3 vs T4, BPdiaand MAP were both significantly higher at T3 than T1 or T2. Bdis and Barea were both significantly higher at T1 than T4. No other measurements were significant for the 80% BFR pressure. CONCLUSIONS: Preliminary results demonstrate that 80% of limb occlusion pressure showed significant differences in both cardiac and hemodynamic responses to BFR potentially due to the pressor reflex that would cause brachial vasodilation along with an increase in HR. While 50% pressure may not cause these same significant responses.

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