Effects of disturbed blood flow during exercise on endothelial function: a time course analysis

Abstract

This study aimed to examine the time course of endothelial function after a single handgrip exercise session combined with blood flow restriction in healthy young men. Nine participants (28 ± 5.8 years) completed a single session of bilateral dynamic handgrip exercise (20 min with 60% of the maximum voluntary contraction). To induce blood flow restriction, a cuff was placed 2 cm below the antecubital fossa in the experimental arm. This cuff was inflated to 80 mmHg before initiation of exercise and maintained through the duration of the protocol. The experimental arm and control arm were randomly selected for all subjects. Brachial artery flow-mediated dilation (FMD) and blood flow velocity profiles were assessed using Doppler ultrasonography before initiation of the exercise, and at 15 and 60 min after its cessation. Blood flow velocity profiles were also assessed during exercise. There was a significant increase in FMD 15 min after exercise in the control arm compared with before exercise (64.09% ± 16.59%, P=0.001), but there was no change in the experimental arm (-12.48% ± 12.64%, P=0.252). FMD values at 15 min post-exercise were significantly higher for the control arm in comparison to the experimental arm (P=0.004). FMD returned to near baseline values at 60 min after exercise, with no significant difference between arms (P=0.424). A single handgrip exercise bout provoked an acute increase in FMD 15 min after exercise, returning to near baseline values at 60 min. This response was blunted by the addition of an inflated pneumatic cuff to the exercising arm.

Figure 1. Flow-mediated dilation (FMD) at baseline, 15 and 60 min after a handgrip exercise bout for both arms. Data are reported as mean±SE. EXP: Experimental arm. *P≤0.01 compared to the same arm at rest; ⁺P≤0.01 compared to the control arm (CON) at the same time point (2×3 repeated-measures ANOVA test).

Figure 2. Flow-mediated dilation (FMD)/shear rate area under the curve (AUC_SR) at baseline and after (15 and 60 min) a handgrip exercise bout for both arms. Data are reported as mean±SE. EXP: experimental arm. *P≤0.05 compared to the control arm (CON) at the same time point (2×3 repeated-measures ANOVA test).

Figure 3. Shear rate profiles at rest and during handgrip exercise for control (CON) and experimental (EXP) arms. A, Rest, with the cuff inflated to 80 mmHg in the EXP arm. B, During exercise, with the cuff inflated to 80 mmHg in the EXP arm. Data are reported as mean±SE. Ant: antegrade, Ret: retrograde. *P≤0.01 compared to the same arm at rest; ⁺P≤0.01 compared to the CON arm at the same time point (2×3 repeated-measures ANOVA test).

Figure 4. Oscillatory shear index at rest (Pre) and during handgrip exercise for control (CON) and experimental (EXP) arms. Data are reported as mean±SE. *P≤0.01 compared to the same arm at rest; ⁺P≤0.01 compared to the CON arm at the same time point (2×3 repeated-measures ANOVA test).

Figure 5. Pearson’s correlation between change in flow-mediated dilation (ΔFMD) at 15 min and the oscillatory shear index.