Blood Flow Restriction Occlusion Pressures Affect Microvascular Oxygenation, Heart Rate, And Pain During Walking

Partial blood flow restriction (BFR) of the exercising musculature during walking has been shown to improve aerobic capacity after training. However, a large range of BFR occlusion pressures can be used (40-80% arterial occlusion pressure, AOP). PURPOSE: This study investigated the effects that varying BFR occlusion pressures have on microvascular oxygenation, heart rate, and pain during continuous walking. METHODS: 22 healthy adults (12 F, 10 M) completed 3 sessions separated by at least 48 hours. During session 1, subjects walked on a treadmill for 15 minutes at a speed that elicited a rating of perceived exertion of 3/10 (CON). During sessions 2-3, subjects walked for 15 minutes at the session 1 speed with application of a randomized occlusion pressure (40% AOP, 40BFR; 80% AOP, 80BFR) applied bilaterally to the proximal thighs. Heart rate (chest strap) and near-infrared spectroscopy (vastus lateralis) sensors were used to continuously record the heart rate (heart rate reserve, %HRR) and microvascular oxygenation (tissue oxygen saturation, StO2; total heme concentration, total[heme]) responses while perceived pain (visual analog scale, 0-100) was recorded every minute throughout the sessions. StO2 and total[heme] were normalized to a 2-minute resting baseline and presented as a delta value (ΔBSL). Since normality was not accepted (Shapiro-Wilk) for any dependent variable, a two-way aligned rank test was used to examine if condition (CON, 40BFR, 80BFR) and/or time (minutes 1-15) affected StO2, total[heme], %HRR, or pain. Statistical significance was set at p < 0.05. RESULTS: Although 80BFR (-25.7 ± 0.9 ΔBSL) deoxygenated the exercising muscle more (lower StO2) than CON (-4.1 ± 1.7 ΔBSL), there were no differences in total[heme] between any conditions. 80BFR (50 ± 5 %HRR) resulted in a higher exercising heart rate compared to 40BFR (23 ± 1 %HRR) and CON (17 ± 1 %HRR). 80BFR (59 ± 9) resulted in higher pain compared to 40BFR (21 ± 3) and CON (0 ± 0). 40BFR had higher pain than CON. CONCLUSION: It is recommended to use a higher occlusion pressure than 40% AOP when walking, as 40BFR did not alter the cardiovascular or local metabolic demand despite increasing pain. It should be considered that 80BFR elicited the highest pain, which may challenge a participant’s exercise tolerance when using BFR walking.