Purpose: The effect of exercise intensity on vasodilator function is poorly understood in children. The authors compared the acute effect of high-intensity interval exercise (HIIE) with moderate-intensity steady-state exercise (MISS) on postexercise vasodilation and shear patterns in 7- to 12- year-old children. Methods: Superficial femoral artery diameter, shear rates, and flow-mediated dilation were measured pre, immediately following (post), and 1 hour after (post60) HIIE (six 1-min sprints at 90% peak power [Wmax], with 1-min recovery) and MISS (15 min at 44% Wmax). Results: Baseline superficial femoral artery diameter increased similarly following both HIIE (pre 4.23 [0.41] mm, post 4.73 [0.56] mm) and MISS (pre 4.28 [0.56] mm, post 4.59 [0.64] mm), returning to preexercise values post60. Blood flow and antegrade shear rate were increased post HIIE and MISS, but to a greater extent, post HIIE (P < .05). Retrograde shear rate was attenuated post both exercise conditions and remained post60 (P < .001). There was a decline in flow-mediated dilation postexercise (HIIE Δ −2.9%; MISS Δ −2.4%), which was no longer apparent when corrected for baseline diameter. Conclusion: Acute bouts of external work-matched HIIE or MISS exert a similar impact on shear-mediated conduit artery vasodilation and flow-mediated dilation in children, and this is reversed 1 hour after exercise.
Ali M. McManus, Nathan R. Sletten and Daniel J. Green
Scott C. Forbes, Nathan Sletten, Cody Durrer, Étienne Myette-Côté, D. Candow and Jonathan P. Little
High-intensity interval training (HIIT) has been shown to improve cardiorespiratory fitness, performance, body composition, and insulin sensitivity. Creatine (Cr) supplementation may augment responses to HIIT, leading to even greater physiological adaptations. The purpose of this study was to determine the effects of 4 weeks of HIIT (three sessions/week) combined with Cr supplementation in recreationally active females. Seventeen females (age = 23 ± 4 yrs; BMI = 23.4 ± 2.4) were randomly assigned to either Cr (Cr; 0.3 g・kg-1・d-1 for 5 d followed by 0.1 g・kg-1・d-1 for 23 days; n = 9) or placebo (PLA; n = 8). Before and after the intervention, VO2peak, ventilatory threshold (VT), time-trial performance, lean body mass and fat mass, and insulin sensitivity were assessed. HIIT improved VO2peak (Cr = +10.2%; PLA = +8.8%), VT (Cr = +12.7%; PLA = +9.9%), and time-trial performance (Cr = -11.5%; PLA = -11.6%) with no differences between groups (time main effects, all p < .001). There were no changes over time for fat mass (Cr = -0.3%; PLA = +4.3%), whole-body lean mass (Cr = +0.5%; PLA = -0.9%), or insulin resistance (Cr = +3.9%; PLA = +18.7%). In conclusion, HIIT is an effective way to improve cardiorespiratory fitness, VT, and time-trial performance. The addition of Cr to HIIT did not augment improvements in cardiorespiratory fitness, performance or body composition in recreationally active females.