Cardiovascular Responses to Blood Flow Restriction and Very Low Load Resistance Exercise in the Upper Body

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Blood flow restriction (BFR) applied as a percentage of arterial occlusion pressure (AOP) combined with low load resistance exercise in the upper body elicits a cardiovascular response that, compared to high-load resistance exercise, appears dependent upon the load as well as the cuff pressure. The response to very low load resistance exercise (15% 1RM) combined with BFR is unknown. PURPOSE: To investigate the cardiovascular and hemodynamic responses to very low load resistance exercise combined with BFR, and compare these to high load resistance exercise in the upper body. METHODS: Sixty-six (50% men) participants (18-35 yrs) were recruited and, following 1RM testing, were randomly assigned to either high load (HL) at 70% 1RM or very low load at 15% 1RM. Very low-load conditions were no restriction (VLL0), 40% AOP (VLL40), or 80% AOP (VLL80) applied using a 5cm cuff. Four sets of unilateral biceps curls were performed to failure or 90 repetitions, whichever occurred first. Blood pressure (SBP/DBP) was taken before and after. Ultrasound measures of blood flow (BF) were taken at rest, following Set 2, and 1 minute after exercise. Repeated measures ANOVA tests were performed to determine whether differences occurred across time and condition. Results presented as mean (SD). RESULTS: Participants were 1.72 (0.1) m tall, weighed 72.0 (13.8) kg, with a 1RM of 15.9 (7.4) kg, and AOP of 103 (73) mmHg. There were no interactions for SBP (p = 0.416), DBP (p = 0.414), but an interaction existed for BF (p < 0.0005). Main effects of time found that SBP [change of 10 (10) mmHg] and DBP [change of 6 (13) mmHg] increased. BF increased following Set 2 in all conditions except for VLL80 (p=0.129), which remained similar to pre until 1 minute post deflation [change of 378 (256) ml·min-1]. Following set 2, BF was similar between VLL0 [547 (244) ml·min-1] and HL [465 (269) ml·min-1]; both were greater than VLL40 [365 (189) ml·min-1] and VLL80 [128 (75) ml·min-1]. At 1 minute post, there were no differences in BF between VLL0: 438 (227), VLL40: 470 (248), VLL80: 464 (290), and HL: 364 (239) ml·min-1. CONCLUSIONS: The hemodynamic response to very low load resistance exercise combined with BFR at different pressures is similar to high load resistance exercise when performed in the upper body, although the BF response differs per the cuff pressure.