Multilevel allometric modelling of maximal stroke volume and peak oxygen uptake in 11-13-year-olds.

ABSTRACT

PURPOSE: To investigate (1) whether maximal stroke volume (SVmax) occurs at submaximal exercise intensities, (2) sex differences in SVmax once fat-free mass (FFM) has been controlled for, and, (3) the contribution of concurrent changes in FFM and SVmax to the sex-specific development of peak oxygen uptake [Formula see text]. METHODS: The peak [Formula see text] s of 61 (34 boys) 11-12-year-olds were determined and their SV determined during treadmill running at 2.28 and 2.50 m s-1 using carbon dioxide rebreathing. The SVmax and peak [Formula see text] of 51 (32 boys) students who volunteered to be tested treadmill running at 2.50 m s-1 on three annual occasions were investigated using multilevel allometric modelling. The models were founded on 111 (71 from boys) determinations of SVmax, FFM, and peak [Formula see text]. RESULTS: Progressive increases in treadmill running speed resulted in significant (p < 0.01) increases in [Formula see text], but SV levelled-off with nonsignificant (p > 0.05) changes within ~ 2-3%. In the multilevel models, SVmax increased proportionally to FFM0.72 and with FFM controlled for, there were no significant (p > 0.05) sex differences. Peak [Formula see text] increased with FFM but after adjusting for FFM0.98, a significant (p < 0.05) sex difference in peak [Formula see text] remained. Introducing SVmax to the multilevel model revealed a significant (p < 0.05), but small additional effect of SVmax on peak [Formula see text]. CONCLUSIONS: Fat-free mass explained sex differences in SVmax, but with FFM controlled for, there was still a ~ 5% sex difference in peak [Formula see text]. SVmax made a modest additional contribution to explain the development of peak [Formula see text] but there remained an unresolved sex difference of ~ 4%.