PREPUBESCENTS VENTILATORY RESPONSES TO EXERCISE WITH REFERENCE TO SEXAND 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-secti onal study of a representative sample of children. Setting: Middle sch ools (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 p ubic hair (no true pubic hair). Measurements: At rest: stature, mass, sum of skinfolds, hemoglobin concentration, FVC, and FEV1. During trea dmill exercise at 7, 8, 9, and 10 km/h, and at peak exercise: oxygen u ptake (V) over dot O-2, minute ventilation ((V) over dot E), tidal vol ume (VT), and respiratory frequency (Rf). Results: At peak exercise, b oys' (V) over dot o(2), (V) over dot E, 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 n o significant (p>0.05) sex differences in Rf or the ratios VT/FVC or ( V) Over dot E. When data were compared at the same relative exercise i ntensity lie, 70 to 75% or 80 to 85% peak (V) over dot o(2), no signif icant (p>0.05) sex differences in Rf, VT/FVC, or (V) over dot E/(V) ov er dot o(2), were detected. Boys' higher (p<0.001) (V) over dot o(2), values were reflected by their higher (V) over dot E which remained hi gher than values for girls at both submaximal levels even when the inf luence of body size was covaried out. Conclusions: Prepubescent boys d emonstrate higher peak (V) over dot o(2) than girls and this is suppor ted by a higher (V) over dot E and (V) over dot T, even when the influ ence of body size is accounted for using allometty. Other ventilatory responses to both peak exercise and exercise at the same relative inte nsity are remarkably similar in both boys and girls.