UBC Theses and Dissertations
Effects of high-intensity interval exercise on vasodilator function in children Sletten, Nathan Robert
Purpose: Exercise training can improve vascular function through anti-atherogenic effects on the vascular endothelium, a response which can be discerned following individual bouts of exercise. Although well characterized in adults, the effect of exercise intensity on the acute recovery patterns of vasodilator function is unknown in children. Study Design: Nine children (age = 10.5 ± 1.5 y, 6 girls) completed 1) high-intensity interval exercise (HIIE, six 1-minute sprints at 90% peak power (Wmax), with 1-minute recovery) and 2) moderate-intensity exercise (MIE, 15 minutes at 44% Wmax, total external work-matched to HIIE). Superficial femoral artery (SFA) diameter, blood flow, shear rates, and flow-mediated dilation (FMD) were measured before (Pre), immediately following (Post), and 60 minutes following (Post60) the exercise trials using duplex ultrasound. Results: Baseline diameter increased similarly following both HIIE (Pre 4.25 ± 0.42 mm, Post 4.76 ± 0.42 mm) and MIE (Pre 4.29 ± 0.49 mm, Post 4.62 ± 0.49 mm), returning to pre-exercise values 60 minutes later. Blood flow and antegrade shear rate were increased following HIIE and MIE, but to a greater extent after HIIE (P < 0.05). Retrograde shear rate was attenuated following both exercise conditions, remaining lower 60 minutes after exercise (P’s < 0.001). FMD was attenuated Post compared to Pre following HIIE (Δ -2.8%) and MIE (Δ -2.5%) (P’s < 0.05) and recovered to pre-exercise values with no difference between Post60 and Pre FMD. When FMD was corrected to account for changes in baseline diameter, there was no longer a significant main effect of time (P = 0.34) making the post-exercise nadir in FMD negligible. Conclusions: Acute bouts of external work-matched HIIE or MIE exert a similar impact on shear-mediated conduit artery vasodilation and FMD in children and this is reversible 60 minutes post-exercise. This suggests the mechanisms that govern the acute FMD response in adolescents and adults may be dissimilar in children.
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