Acute physiological responses to low-intensity blood flow restriction cycling

Objectives: Blood flow restriction (BFR) during interval cycling may stimulate aerobic and anaerobic adaptations. However, acute physiological responses to BFR interval cycling have not been extensively investigated. Design: Eighteen males completed low-intensity (LI), low-intensity with BFR (LIBFR) and high-intensity (HI) interval cycling sessions in randomised and counterbalanced order. These included a standardised warm-up and three two-min intervals interspersed with two-min recovery. Interval intensity during HI, LI and LIBFR were 85%, 40% and 40% of peak power output obtained during graded exercise tests. Methods: During LIBFR, 80% arterial occlusion was applied to both legs during the interval efforts and removed during recovery. Continuous measures of heart rate (HR), cardiac output (CO) and oxygen consumption ((V) over dotO(2)) were recorded. Blood pressure (BP) and rating of perceived exertion (RPE) were measured following intervals. Blood lactate concentration was measured pre- and post-exercise. Results: BP, HR, CO, (V) over dotO(2), lactate and RPE were greatest during HI. During the active intervals, BP, HR and CO were greater during LIBFR than LI. (V) over dotO(2) during recovery periods were greater in LIBFR than LI. Post session lactate was greater during LIBFR than LI. Importantly, mean arterial pressure during interval three was significantly greater in LIBFR (124 +/- 2 mmHg) than HI (114 +/- 3 mmHg). Conclusions: LIBFR increases cardiovascular and metabolic stress compared with LI and could provide an alternative aerobic training method for individuals unable to perform high-intensity exercise. However, increases in mean arterial pressure during LIBFR indicates high myocardial workload, and practitioners should therefore use caution if prescribing LIBFR for vascular compromised individuals. (C) 2018 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.