Approximate entropy showed greater tidal volume and breathing frequency variability during steady state exercise in healthy adolescents compared to adults

Abstract

Introduction: During incremental exercise breathing frequency (B f ) and tidal volume (V T ) increase to ensure that minute ventilation (V E ) meets the metabolic demands of exercise. The control of exercise ventilation, which comprises of feedback and feedforward mechanisms, is challenged during adolescence by physiological changes in respiratory system characteristics. Our previous work showed that healthy adolescents demonstrate unstable ventilation during incremental exercise compared to the relatively stable breathing patterns of healthy adults. However, we were unable to objectively quantify these breathing patterns due to the increasing workload profile of incremental exercise. Approximate entropy (ApEn) is a non-linear method which can be used to quantify the unpredictability of ventilatory data. Aim/hypothesis: The objective of this study was to apply ApEn analysis to quantify and compare breathing patterns during steady state exercise in healthy physically active adolescent and adult subjects. We hypothesised that ApEn would be greater (i.e. more variable) in adolescent compared to adult subjects. Method: Two groups were recruited: the adolescent group (n=12, 5M:7F) aged 12-14 years and the adult group (n=9, 4M:5F) aged 25-35 years. Participants performed 20-minutes of steady state exercise on a cycle ergometer at a workload of 1 W·kg -1 of body weight. ApEn was performed for V T , B f and V E over the final 15-minutes of exercise to ensure steady-state exercise breathing patterns were adopted. The Mann-Whitney U test compared the between group ApEn results. Results: Significantly greater ApEn results were observed in the adolescent group compared to the adult group for V T (1.28 ± 0.05 vs. 1.12 ± 0.11, p<0.05) and B f (1.31 ± 0.07 vs. 1.19 ± 0.11, p<0.01) but not V E (1.25 ± 0.13 vs. 1.03 ± 0.23). Conclusion: Using ApEn we showed greater variability of V T and B f for healthy adolescents compared to healthy adults. This supports the results of our previous studies of maximal exercise. We suggest that the greater variability of breathing patterns observed in the adolescent group likely reflects the normal development and maturation of ventilatory control and should not be viewed as abnormal. This research was supported by an award from The Green Lane Research and Education Fund Board. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.