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Background and objectives: Given the growing prevalence of obesity in children, the present study aimed to investigate effects of continuous and interval aerobic training on insulin resistance index and serum cortisol levels of obese girls.
Methods: The study was performed on 36 healthy girls aged 9-11 years with a body mass index (BMI) of higher than 85th percentile. The subjects were randomly divided into three groups of interval training, continuous training and control. The training groups performed exercises three days a week for eight weeks. The exercises were performed at 70% of VO2max in the first four weeks and at 80% of VO2max in the following weeks. Fasting blood samples were taken 72 hours before the first session and 72 hours after the last training session in order to measure levels of cortisol, glucose, insulin and Homeostatic Model Assessment for Insulin Resistance (HOMA-IR).Weight, BMI and body fat percentage were also measured by conventional methods. Data analysis was performed in SPSS 21 using paired t-test and one-way analysis of variance.
Results: The mean level of BMI and body fat percentage decreased significantly after the interval and continuous training, respectively (P<0.05). The HOMA-IR index did not change significantly in the study groups (P>0.05). The cortisol level increased slightly in the continuous training and control groups (P=0.075) and decreased insignificantly (P=0.131) in the interval training group. There was no difference between the training groups and the control group in terms of HOMA-IR and cortisol levels.
Conclusion: Insulin levels, HOMA-IR showed a decrease trend while a reasonable increase in cortisol level we showed in the continuous training group. BMI level and fat percentage decreased in two both training groups.

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