Cardiovascular And Perceptual Responses To Various Blood Flow Restriction Pressures And Exercise Loads

Abstract

Blood flow restriction (BFR) allows individuals to exercise with lower loads while producing similar increases in muscle size as high load training. Most studies implement moderate to high pressures with loads corresponding to 20-30% of their one-repetition maximum (1RM). No study has examined perceptual or cardiovascular responses using loads lower than 20% 1RM, which may provide a more widely inclusive and palatable stimulus. PURPOSE: To determine the cardiovascular and perceptual response to very low load BFR exercise using both moderate (40%) and high (80%) relative arterial occlusion pressures (AOP). METHODS: 14 participants came to the lab on four separate days to complete six exercise protocols (2 per visit on visits 2-4) consisting of 4 sets (1 set of 30 followed by 3 sets of 15) of BFR elbow flexion exercise with either a 10%, 15% or 20% 1RM load, each of which was performed with a moderate (40% AOP) and high (80% AOP) relative pressure. A repeated measures ANOVA was used to determine differences in AOP pre and post exercise and a Friedman test was used to determine differences in discomfort and ratings of perceived exertion (RPE) following each set. AOP is expressed as [mean (95% confidence interval)] with RPE and discomfort expressed as [median (25th, 75th percentile)]. RESULTS: There was an interaction for AOP (p=0.002) with higher pressures and loads producing a gradient increase. The pre to post changes ranged from 21 (95% CI: 10-32) mmHg in the 10% 1RM/40% AOP condition to 62 (95% CI: 45-78) mmHg in the 20% 1RM/80% AOP condition. Ratings of discomfort were primarily dependent on the level of restriction pressure applied, with higher pressures resulting in greater discomfort (p<0.001) ranging from 2.5 (1, 5) in the 15% 1RM/40% AOP condition to 6.5 (5.5, 7.25) in the 15% 1RM/80% AOP condition. Additionally, a gradient increase in RPE accompanied higher pressures and loads which ranged from 8.5 (7,12) at the conclusion of the 10%1RM/40% AOP condition to 15.5 (12.75, 17.25) at the conclusion of the 20% 1RM/80% AOP condition. CONCLUSIONS: Increases in load and restrictive pressure resulted in elevated AOP and RPE, but higher pressures were primarily responsible for increased discomfort. Individuals experiencing discomfort during low load BFR exercise may wish to decrease the applied pressure and increase the exercise load.