Development of Ventilatory Responses to Exercise in Normal White Children (Introduction)

Development of Ventilatory Responses to Exercise in Normal White Children (Introduction)Cross-sectional studies have indicated that the pattern of ventilatory responses to exercise evolves during the course of childhood. This 5-year study was designed to provide a longitudinal assessment of minute ventilation (Ve), tidal volume (Vt), and breathing frequency (fR) in 20 children (11 girls, nine boys) between the ages of 9 and 13 years. Subjects performed maximal and identical submaximal steady-state treadmill walking tests annually. No significant gender differences were observed in any of the three variables. At submaximal exercise, Vt per kilogram remained stable, with a progressive fall in fR. As a result, submaximal Ve per kilogram declined with age. A similar pattern was observed at maximal exercise, but the decrease in Ve per kilogram was not statistically significant. Ventilatory equivalent for oxygen (Ve/Vo2) fell with age at submaximal exercise but declined only in the boys with maximal testing. Ve/Vo2 at maximal and submaximal exercise was greater in the girls at all ages. These findings support previous data derived from cross-sectional studies.

Knowledge of the normal course of developmental exercise physiology is important in understanding aerobic fitness in the pediatric population. To this end, a series of cross-sectional investigations has provided a composite picture of the changes in ventilatory response to exercise in growing children.’ In general, these studies have indicated that increases in maximal and submaximal ventilation and tidal volume (Vt) during the course of childhood are closely linked to age. Over the same period, breathing rate and ventilatory equivalent for oxygen (Ve/ Vo2) in response to exercise progressively decline.

Longitudinal data regarding ventilatory changes in exercising children are limited, confined to a single study of Norwegian children between ages 8 and 15 years. In that investigation, ventilatory responses were observed during cycle testing, and submaximal values were reported at similar relative rather than absolute exercise intensities. In general, findings mimicked those of the cross-sectional reports.

This 5-year longitudinal study was conducted to expand our understanding of the normal changes of ventilatory responses to exercise during childhood. Maximal and submaximal data were obtained annually from treadmill testing, with submaximal values determined at the same speed and slope. Particular attention was focused on the means by which these serial measurements related to changes in body size.

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