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Prepubescents' ventilatory responses to exercise with reference to sex and body size.

STUDY OBJECTIVES
To examine the ventilatory responses of prepubescent children to submaximal and peak exercise using appropriate allometric modeling to control for differences in body size.


DESIGN
Cross-sectional study of a representative sample of children.


SETTING
Middle schools (8 to 11 years) in Exeter, UK.


PARTICIPANTS
We studied 101 boys and 76 girls aged 11.1 (0.4) years and classified Tanner stage 1 for pubic hair (no true pubic hair).


MEASUREMENTS
At rest: stature, mass, sum of skinfolds, hemoglobin concentration, FVC, and FEV1. During treadmill exercise at 7, 8, 9, and 10 km/h, and at peak exercise: oxygen uptake (VO2), minute ventilation (VE), tidal volume (VT), and respiratory frequency (Rf).


RESULTS
At peak exercise, boys' VO2, VE, and VT were significantly (p<0.01) higher than girls' values and remained so even when the influence of body size was controlled using allometric principles. There were no significant (p>0.05) sex differences in Rf or the ratios VT/FVC or VE/VO2. When data were compared at the same relative exercise intensity (ie, 70 to 75% or 80 to 85% peak VO2), no significant (p>0.05) sex differences in Rf, VT/FVC, or VE/VO2 were detected. Boys' higher (p<0.001) VO2 values were reflected by their higher VE which remained higher than values for girls at both submaximal levels even when the influence of body size was covaried out.


CONCLUSIONS
Prepubescent boys demonstrate higher peak VO2 than girls and this is supported by a higher VE and VT, even when the influence of body size is accounted for using allometry. Other ventilatory responses to both peak exercise and exercise at the same relative intensity are remarkably similar in both boys and girls.