Acute Effects of Blood Flow Restriction Cuffs During Aerobic Exercise on Hemodynamics in Females

Abstract

PURPOSE: The purpose of this study was to investigate the acute effects of a 20-minute walk/run at 40% VO2 with and without blood flow restriction (BFR) cuffs on pulse rate (PR), stroke volume (SV), cardiac output (CO), cardiac ejection time (CET), systemic vascular resistance (SVR) and total vascular impedance (TVI) when compared to a 60-minute walk/run at 65% VO2 without BFR in females. METHODS: Seventeen female subjects, between the ages of 18 and 40, were familiarized with the study protocol, had thigh circumference (THC) measured, and performed the Bruce protocol on the first day. BFR cuff inflation was based on THC. The three randomized sessions: 1) 40% VO2 with BFR for 20 minutes (BFR-20min), 2) 40% VO2 without BFR for 20 minutes (no-BFR-20min), and 3) 65% VO2 without BFR for 60 minutes (no-BFR-60min). Each session began with the subject reaching a hydration status at or below 1.010. Once the hydration levels were reached, the subject would lie down, in the supine position, and have baseline hemodynamics measured. Following baseline measurements, the subject walked/ran at a randomly predetermined intensity and time with or without BFR cuffs. BFR cuffs were taken off immediately after the 20-minute BFR condition. Post measurements of hemodynamics were taken at 10, 20, and 40 minutes following exercise. Conditions were separated by at least 48 hours. RESULTS: Significant condition main effects were found in PR (p<.01, BFR-20min vs. no-BFR-60min), SV (p<.01, BFR-20min vs. no-BFR-60min), CET (p<.04 no-BFR-20min vs. no-BFR-60min). Significant time main effects were found in PR (p<.01), SV (p<.01), CO (p<.04), CET (p<.01), SVR (p<.04), and TVI (p<.01). Significant condition*time interactions were found in PR (p<.01), SV (p<.01), CO (p<.02), SVR (p<.04), and TVI (p<.01). CONCLUSIONS: The BFR-20min condition, at 40% VO2, elicited higher SV and lower PR responses than the no-BFR-60min condition using 65% VO2, which might be caused by the use of a lower intensity that produced a lower sympathetic nervous system response. Furthermore, the no-BFR-60min condition produced a lower response in SVR and TVI than the no-BFR-20min condition that may have been caused by a greater release of nitric oxide from the session length that was thrice as long.