The main objectives of the present study were to determine acute and chronic effects of supra-high intensity interval training (supra-HIIT) on energy expenditure and vascular function in obese prepubescent boys. Obese prepubescent boys, aged 8 - 12 years, participated in this series of studies. The participants had BMI ≥ +2 SD above the growth reference data for boys aged 5-18 years. This research was divided into 2 studies. Study 1, eighteen lean and seventeen obese prepubescent boys were asked to perform supra-high intensity interval training at 100, 130 and 170% VO2peak. The Measurements of energy expenditure and vascular function were assessed before and after each exercise session. A 2x3 (group x exercise intensity) ANOVA with repeated measures followed by LSD’s multiple comparisons was used to analyze the data. The results from the 1st study were used to set exercise intensity for study 2. Thirty seven obese prepubescent boys were randomly assigned into three groups including control group (CON; n=11), HIIT at 90% VO2peak (Total exercise time = 24 min) (HIIT; n=11) and supra-HIIT at 170% VO2peak (Total exercise time = 14 min) (supra-HIIT; n=15). Both exercise groups were asked to perform exercises on a mechanically-braked cycle ergometer 3 times/week for 12 weeks. A 3x2 (group x time) ANOVA with repeated measures followed by LSD’s multiple comparisons was used to analyze the data. The results of the present study were as follows 1. For the study 1, the obese group had significantly greater total energy expenditure in all three HIIT intensities than the lean group. Brachial-ankle pulse wave velocity (baPWV) decreased significantly after HIIT at 130 and 170% VO2peak in both lean and obese groups. Only the HIIT at 170% VO2peak demonstrated greater flow mediate vasodilatation (FMD) compared with the baseline. 2. For the study 2, after 12 weeks, supra-HIIT and HIIT had significantly greater resting energy expenditure than the control group (p<0.05). There were no significant differences in BMI, body weight and body fat following CON, HIIT and supra-HIIT. Artery wall thickness and baPWV decreased in supra-HIIT. Cholesterol and triglyceride decreased and nitric oxide level increased in both HIIT and supra-HIIT (all p<0.05). There were no significant differences in creatine phosphokinase and malondialdehyde following both HIIT and supra-HIIT. Physical activity enjoyment score in supra-HIIT was significantly higher than HIIT (p<0.05). In conclusion, supra-HIIT performed at the intensity of 170% VO2peak can be a feasible exercise modality for improving vascular structure and function in obese prepubescent boys. Moreover, it requires much less time to complete, provides no muscle damage and make enjoyment in obese children.
