Exercise training associated with diet improves heart rate recovery and cardiac autonomic nervous system activity in obese children.

The purpose of this study was to test the hypotheses that in obese children: 1) hypocaloric diet (D) improves both heart rate recovery at 1 min (ΔHRR1) cfter an exercise test, and cardiac autonomic nervous system activity (CANSA) in obese children; 2) Diet and exercise training (DET) combined leads to greater improvement in both ΔHRR1 after an exercise test and in CANSA, than D alone. Moreover, we examined the relationships among ΔHRR1, CANSA, cardiorespiratory fitness and anthropometric variables (AV) in obese children submitted to D and to DET. 33 obese children (10±0.2 years; body mass index (BMI) >95 th percentile) were divided into 2 groups: D (n=15; BMI=31±1kg/m 2 ) and DET (n=18; 29±1 kg/m 2 ). All children performed a maximal cardiopulmonary exercise test on a treadmill. The ΔHRR1 was defined as the difference between heart rate at peak and at 1-min post-exercise. CANSA was assessed using power spectral analysis of heart rate variability at rest. The sympathovagal balance (low frequency and high frequency ratio, LF/HF) was measured. After interventions, all obese children showed reduced body weight (P 0.05). In contrast, the DET group showed increased peak VO 2 (P=0.01) and improved ΔHRR1 (ΔHRR1 =37.3+2.6; P=0.01) and LF/HF ratio (P=0.001). The DET group demonstrated significant relationships among ΔHRR1, peak VO 2 and CANSA (P<0.05). In conclusion, DET, in contrast to D, promoted improved ΔHRR1 and CANSA in obese children, suggesting a positive influence of increased levels of cardiorespiratory fitness by exercise training on cardiac autonomic activity.