Background: Endothelial dysfunction is associated with childhood obesity and is closely linked to the amount and function of endothelial progenitor cells. However, it remains unclear whether endothelial progenitor cells increase with after-school exercise in overweight and obese children. The purpose of this study was to investigate the effects of an after-school exercise programme on endothelial cell function in overweight and obese children.Methods: A total of 29 overweight/obese children (12.2 ± 0.1 years) were randomly divided into control (i.e. no after-school exercise, n = 14) and after-school exercise (n = 15) groups. The 12-week after-school exercise intervention consisted of 3 days of combined aerobic and resistance exercise per week. Each 80-minute exercise programme included 10 minutes of warm-up and 10 minutes of cool-down after school. CD34+ (a cell surface marker on hematopoietic stem cells), CD133+ (a cell surface marker on hematopoietic progenitor cells) and CD34+/CD133+ (considered as endothelial progenitor cells) were measured at baseline and after 12 weeks using flow cytometry.Results: Increased percentages of CD34+, CD133+ and CD34+/CD133+ cells were observed in the after-school exercise group (p = 0.018; p = 0.001; p = 0.002, respectively) compared with the control group. Carotid intima-media thickness decreased after 12 weeks in the after-school exercise group (p = 0.020) compared with the control group.Conclusions: This study provides preliminary evidence that a combined after-school exercise programme may represent an effective intervention strategy for improving vascular repair and endothelial cell function, leading to improved cardiovascular health in overweight and obese children.Trial registration: Current Controlled Trials ISRCTN19037201.
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