Low‐ and high‐volume blood‐flow restriction treadmill walking both improve maximal aerobic capacity independently of blood volume

Abstract

AbstractAimAssess the effect of low‐ and high‐volume blood flow restriction training (BFR) on maximal aerobic capacity (VO2max) and determine if alteration in VO2max is mediated through changes in hemoglobin mass (Hbmass) and blood volume.MethodsParticipants' Hbmass (CO‐rebreathe), single, and double‐leg VO2max and blood volume regulating hormonal responses (renin and copeptin) were measured before and after BFR training. Training consisted of treadmill walking either (1) twice‐daily for 4week (CON and BFRHV) or (2) twice‐weekly for 6week (BFRLV). Each session consisted of five intervals (3 min, 5% incline, 5 km/h, 100% of lowest occlusion pressure), with 1 min of standing rest between sets.ResultsVO2max increased using both training exposures, in as quickly as 2‐weeks (BFRLV baseline to 4week: +315 ± 241 mL (8.7%), p = 0.02; BFRHV baseline to 2week: +360 ± 261 mL (7.9%), p < 0.01), for the BFRLV and BFRHV groups, with no change in CON. Single‐ and double‐leg VO2max improved proportionately (single/double‐leg VO2max ratio: BFRLV 78 ± 4.9–78 ± 5.8%, BFRHV 79 ± 6.5–77 ± 6.5%), suggesting that the mechanism for increased VO2max is not solely limited to central or peripheral adaptations. Hbmass remained unchanged across groups (CON: +10.2 ± 34 g, BFRLV: +6.6 ± 42 g, BFRHV: +3.2 ± 44 g; p = 0.9), despite a significant release of blood volume regulating hormones after initial BFR exposure (renin +20.8 ± 21.9 ng/L, p < 0.01; copeptin +22.0 ± 23.8 pmol/L, p < 0.01), which was blunted following BFRHV training (renin: +13.4 ± 12.4 ng/L, p = 0.09; copeptin: +1.9 ± 1.7 pmol/L, p = 0.98).ConclusionBFR treadmill walking increases VO2max irrespective of changes in Hbmass or blood volume despite a large release of blood volume regulating hormones in response to BFR treadmill walking.