Effect of asthma and six-months high-intensity interval training on heart rate variability during exercise in adolescents.

Little is known regarding the influence of asthma and exercise, and their interaction, on heart rate variability (HRV) in adolescents. Thirty-one adolescents with asthma (13.7±0.9 years; 21.9±3.9 kg·m-2; 19 boys, 12 girls) and thirty-three healthy adolescents (13.8±0.9 years; 20.3±3.2 kg·m-2; 16 boys, 17 girls) completed an incremental ramp test and three heavy-intensity constant-work-rate cycle tests. Thirteen adolescents (7 boys, 6 girls; 6 asthma, 7 control) completed six-months high-intensity interval training (HIIT) and were compared to age- and sex-matched controls. Standard time-domain, frequency-domain and non-linear indices of HRV were derived at baseline, three- and six-months. Asthma did not influence HRV at baseline or following HIIT. Total power, low frequency and normalised low frequency power, and sympathovagal balance increased at three-months in HIIT, subsequently declining towards baseline at six-months. Normalised high frequency power was reduced at three-months in both groups, which was sustained at six-months. No effects of HIIT were observed in the time-domain nor in the non-linear indices. HRV was not influenced by asthma, potentially because such derangements are a function of disease progression, severity or duration. HIIT may be associated with a short-term shift towards greater sympathetic predominance during exercise, perhaps caused by physiological overload and fatigue.

The relationship between body mass index, aerobic performance and asthma in a pre-pubertal, population-level cohort.

PURPOSE: To assess the relationship between asthma, body mass index (BMI) and aerobic performance, as indicated by a shuttle test. METHODS: 20,577 participants (10,413 boys) from the SportsLinx serial cross-sectional study participated. Parental reports of asthma status and home postcode data were gathered from consent forms. Stature, sitting stature and body mass were measured and BMI, somatic maturity and indices of multiple deprivation scores (IMD) were derived. Performance on the 20 m multi-stage shuttle runs test (20mSRT) was used to estimate cardiorespiratory fitness (CRF). RESULTS: Asthma [F (1, 17,015) = 82.26, P < 0.01] and gender [F (1, 17,015) = 678.491, P < 0.001] significantly influenced 20mSRT. The addition of BMI, maturity and IMD to the model did not alter these significant effects. There was a significant interaction between 20mSRT and BMI [F (1, 16,723) = 132.80, P < 0.01], with a significant decrease in 20mSRT from the 50th BMI percentile upwards [t (16,699) = 36.88, P < 0.01]. Binary logistic regression revealed gender and 20mSRT to be significant predictors of asthma occurrence; BMI SDS just reached significance whilst maturity and IMD were not significant contributors to the model. CONCLUSIONS: This study demonstrates the negative influences of low CRF and high BMI on the risk of asthma occurrence in pre-pubertal children. Furthermore, it highlights the significant influence of BMI on CRF, revealing these effects to be manifest considerably below those BMI percentiles conventionally associated with being overweight or obese.