Effects of Different Levels of Blood Flow Restriction on Arterial Occlusion Pressure and Perceptual Responses

Abstract

Low load exercise with blood flow restriction (BFR) increases muscle size similar to high load exercise. Studies have investigated relative restriction pressures ranging from 40% - 90% of resting arterial occlusion pressure (AOP) during BFR exercise, however, no studies have investigated relative restriction pressures below 40% AOP. PURPOSE: To characterize the cardiovascular and perceptual responses to pressures below 40% AOP and compare them to a moderate (50% AOP) and higher (90% AOP) relative pressure. METHODS: Twenty-six participants performed four sets of unilateral elbow flexion using 30% of their one-repetition maximum (1RM) while a 5cm wide nylon cuff was placed at the proximal portion of their upper arm. The cuff was inflated to one of six relative restriction pressures (0%, 10%, 20%, 30%, 50%, 90% AOP). AOP was measured before (pre) and immediately after four sets (post) of exercise at the radial artery. Ratings of perceived exertion (RPE) and discomfort were taken prior to (pre) and following each set of exercise. A repeated measures ANOVA determined differences in AOP. A Friedman test was used to determine differences for perceptual responses. Data presented as mean (95% CI) except for perceptual responses represented as the 25th, 50th, 75th percentiles. Statistical significance was set at p≤0.05. RESULTS: AOP increased from pre to post (p < 0.001) in all conditions but was augmented further with higher pressures [e.g. 0%: 36 (30 - 42) mmHg vs. 10%: 39 (34 - 44) mmHg vs. 90% 46 (41 - 52) mmHg]. For RPE and discomfort, there were significant differences across conditions for all sets of exercise (p < 0.01) with RPE [e.g. 0%: (13, 14.5, 17) vs. 10%:(12, 13.5, 17) vs. 90%: (14.7, 17.0, 19.0) during last set] and discomfort [e.g. 0%: (1.5, 3.5, 6.2) vs. 10%: (1, 3, 6) vs. 90%: (4.5, 7.0, 9.0) during last set] generally being greater at higher restriction pressures. CONCLUSIONS: The results provide additional information to the BFR literature by categorizing the cardiovascular and perceptual response to pressures < 40% AOP. The cardiovascular response is different depending on the relative restriction pressure applied. These findings may guide future studies to provide a safer and more tolerable stimulus for the individual who still wants to increase muscle size while concomitantly minimizing the cardiovascular response.