Effects of high-intensity intermittent training on cardiac autonomic modulation of adolescents with obesity

OBJECTIVE: To investigate the impact of high-intensity interval training (HIIT) on autonomic regulation in obese adolescents. METHODS: The study sample included 26 adolescents with obesity, of both sexes, aged 12 ± 2 years, divided into a control group (n = 11) and a training group (n = 15). Anthropometric assessments included body weight and height for the calculation of body mass index (BMI), as well as sitting height to estimate Maturity Offset. Body fat percentage was obtained through dual-energy X-ray absorptiometry (DEXA). Heart rate variability (HRV) was analyzed with the Polar RS800 heart rate monitor, using time-domain, frequency-domain, and Poincaré plot parameters. The intervention involved an HIIT protocol on a treadmill over 20 weeks, performed three times a week, consisting of a warm-up, followed by six 40-s high-intensity bouts at a running speed equivalent to 100 % of the peak heart rate determined by a maximal effort test, interspersed with 20-s passive recovery intervals. Each session also included 4 min of passive recovery at a constant speed of 5 km/h or 50 % of the training speed, after which the training cycle was repeated. Statistical tests included the Shapiro-Wilk test, independent t-tests, and repeated measures ANOVA, conducted using SPSS version 13.0. RESULTS: After the 20-week training period, no significant changes were found in HRV indices across the time-domain, frequency-domain, or Poincaré plot analyses. CONCLUSION: A 20-week HIIT protocol did not lead to measurable changes in cardiac autonomic modulation in adolescents with obesity.