Comparison of the effects of aquatic HIIT and MICT on central hemodynamics, endothelial function, and aerobic fitness in obese school-aged children: a randomized controlled trial

Aquatic exercise may be a feasible strategy for improving cardiovascular health in children with obesity, but evidence comparing aquatic high-intensity interval training (aHIIT) and aquatic moderate-intensity continuous training (aMICT) remains limited. This pilot randomized controlled trial compared the effects of 8 weeks of aHIIT and aMICT on endothelial function, estimated cardiorespiratory fitness, central hemodynamic indices, arterial stiffness, and anthropometric indicators in school-aged children with obesity. Thirty-three children with obesity were randomized to the aHIIT group ( n = 11), aMICT group ( n = 11), or non-exercise control group ( n = 11). The two aquatic exercise groups trained 3 days/week for 8 weeks. The aHIIT protocol consisted of 10 × 30-s high-intensity aquatic exercise (such as freestyle swimming or freestyle kicking) bouts at 80%-90% HRmax, separated by 60-s recovery intervals, whereas the aMICT protocol consisted of two 15-min continuous breaststroke bouts at 60%-70% HRmax, separated by a 5-min recovery interval. Brachial artery flow-mediated dilation (FMD) was used as the principal vascular outcome. Central hemodynamic indices were assessed using applanation tonometry, and estimated VO 2max was obtained from the 20-m shuttle run test. Intervention effects were analyzed using two-way repeated-measures ANOVA, with the group × time interaction used as the primary test for differential intervention effects. Significant group × time interactions were observed for estimated VO 2max , FMD, AIx, and AIx@HR75. Estimated VO 2max increased in both aquatic exercise groups compared with the control group. FMD improved in both exercise groups, with a greater increase observed after aHIIT. AIx and AIx@HR75 showed favorable changes after aMICT. No significant group × time interactions were observed for resting blood pressure, SEVR, ABI, cfPWV, or baPWV. This pilot trial suggests that both aHIIT and aMICT may improve estimated cardiorespiratory fitness in school-aged children with obesity. aHIIT may be associated with greater improvement in brachial artery endothelial function, whereas aMICT may have favorable effects on selected wave-reflection-related indices. However, these findings should be interpreted cautiously because of the small sample size, indirect estimated VO 2max estimation, lack of maturation assessment, and unmatched exercise workload. Chinese Clinical Trial Registration, ChiCTR2400080687.05/02/2024.