Sam Robert Emerson1,Stephanie P. Kurti1, Sara K. Rosenkranz2, Joshua R. Smith1,&Craig A. Harms1, FACSM 1Departments of Kinesiology and 2Human Nutrition, Kansas State University, Manhattan, Kansas

Ventilatory constraint, i.e. expiratory flow limitation (EFL), during exercise leads to an increased work of breathing, dyspnea, respiratory muscle fatigue, and adverse cardiovascular outcomes which can all affect exercise tolerance. EFL is due to an imbalance between pulmonary capacity and ventilatory demand during exercise. We have recently reported that EFL is highly prevalent in prepubescent children and is much greater than that reported in adults. It is unknown how maturation from pre- to post-puberty affects pulmonary function, specifically EFL, during exercise. PURPOSE: Therefore, the purpose of this longitudinal study was to investigate the changes in cardiopulmonary function from pre- to post-puberty. METHODS: Nineteen children (ages 12-16 yrs; 10 boys, 9 girls) were recruited from 40 prepubescent children who completed testing in our lab ~5 years ago. Subjects completed pulmonary function tests (PFTs) before and after an incremental exercise test to exhaustion (VO2max) on a cycle ergometer. EFL was determined using the percent tidal volume (VT) overlap method. RESULTS: Sixteen of the 19 subjects (8 boys, 8 girls; 84%) exhibited EFL pre-puberty. Six of the 19 subjects (4 boys, 2 girls; 32%) exhibited EFL post-puberty. Of the subjects that experienced EFL post-puberty, all had experienced EFL pre-puberty. Forced vital capacity (FVC) significantly increased (~100%) from 2.1 ± 0.4 L (mean ± SD) at the pre-puberty assessment to 4.3 ± 0.7 L at the post-puberty assessment. Absolute VO2max significantly increased (~125%) from 1.09 ± 0.3 L/min to 2.38 ± 0.6 L/min; relative VO2max significantly increased (~23%) from 32.4 ± 8.4 ml/kg/min to 38.1 ± 7.3 ml/kg/min.Maximal ventilation significantly increased (~120%) from 46.4 ± 10.3 L/min to 98.6 ± 20.8 L/min. VE/VCO2 coupling at VO2max significantly decreased (~12%) from 43.5 ± 6.4 at pre-puberty to 37.5 ± 4.0 at post-puberty. CONCLUSION: These data suggest that the prevalence of EFL declines as children mature from pre- to post-puberty, likely due to greater increase in lung volume (FVC) than increases in VEmax and VO2max, accompanied by a decrease in VE/VCO2 coupling. This increase in pulmonary function at maximal exercise may contribute to the improved exercise capacity seen in adolescents and adults compared to children.

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