Cardiovascular Responses To Aerobic Exercise With Continuous And Discontinuous Blood Flow Restriction

Abstract

During low-intensity (LI) aerobic exercise with blood flow restriction (BFR), restriction cuffs could be inflated continuously during the entire protocol (CONT BFR) or inflated discontinuously (DISC BFR); inflated during work intervals (INTs) and deflated during recovery. The effect of various restriction durations on cardiac work is unclear. PURPOSE: This study examined local stress and cardiac work in response to INT protocols of LI with CONT BFR and DISC BFR, and LI and high-intensity (HI) without BFR. METHODS: Healthy males randomly performed the 4 protocols. Each consisted of 5 2-min INTs with 1-min recovery (20 W). INTs for DISC BFR, CONT BFR, and LI were 35% of peak work rate. INTs for HI were 70% of peak work rate. In DISC BFR, cuff were inflated during INTs and deflated during recovery. In CONT BFR, cuffs were inflated at the start of INT 1 and remained inflated until the end of INT 5. Restriction pressure was 60% of limb occlusion pressure. Oxygen uptake (VO2) and tissue oxygen saturation (StO2, %), measured by near-infrared spectroscopy, were recorded continuously and averaged over last 30 s of INTs 1, 3, and 5. StO2 values were reported as change from baseline (20 W) (∆BSL) and used to quantify local stress. Blood pressure was taken manually during the last 30 s of INT 1, INT 3, and INT 5. Rate pressure product (RPP) was calculated from heart rate and systolic blood pressure to assess cardiac work. RESULTS: VO2 was similar between CONT BFR (INT 5 = 1.44 ± 0.19 L*min-1), DISC BFR (INT 5 = 1.36 ± 0.15 L*min-1), and LI (INT 5 = 1.37 ± 0.20 L*min-1), but were lower than HI (INT 5 = 2.30 ± 0.25 L*min-1). In all INTs, StO2 was similar between CONT BFR (INT 5 = -23.2 ± 13.8 ∆BSL), DISC BFR (INT 5 = -20.1 ± 9.2 ∆BSL) and HI (INT 5 = -24.7 ± 12.2 ∆BSL). In INT 5, DISC BFR was greater than LI (-2.5 ± 15.8 ∆BSL); CONT BFR and HI were greater than LI during INT 3 and INT 5. In all INTs, RPP was not different between CONT BFR (INT 5 = 20850.4 ± 2541.0 mmHg*BPM) and DISC BFR (INT 5 = 20899.1 ± 2857.1 mmHg*BPM), but both were lower than HI (INT 5 = 30905.5 ± 1768.1 mmHg*BPM). LI (INT 5 = 17448.8 ± 2275.8 mmHg*BPM) was lower than all protocols. CONCLUSION: DISC BFR and CONT BFR produced similar local stress and cardiac work. Compared to HI, LI with BFR, regardless of restriction duration, produced similar local stress with lower cardiac work, either protocol could be suitable for BFR exercise.