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

Purpose To investigate (1) whether maximal stroke volume (SV max ) occurs at submaximal exercise intensities, (2) sex differences in SV max once fat-free mass (FFM) has been controlled for, and, (3) the contribution of concurrent changes in FFM and SV max to the sex-specific development of peak oxygen uptake ( V̇O₂ ) V˙O2 . Methods The peak V̇O₂ V˙O2 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 SV max and peak V̇O₂ V˙O2 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 SV max , FFM, and peak V̇O₂ V˙O2 . Results Progressive increases in treadmill running speed resulted in significant ( p < 0.01) increases in V̇O₂ V˙O2 , but SV levelled-off with nonsignificant ( p > 0.05) changes within ~ 2–3%. In the multilevel models, SVmax increased proportionally to FFM 0.72 and with FFM controlled for, there were no significant ( p > 0.05) sex differences. Peak V̇O₂ V˙O2 increased with FFM but after adjusting for FFM 0.98 , a significant ( p < 0.05) sex difference in peak V̇O₂ V˙O2 remained. Introducing SV max to the multilevel model revealed a significant ( p < 0.05), but small additional effect of SVmax on peak V̇O₂ V˙O2 . Conclusions Fat-free mass explained sex differences in SV max , but with FFM controlled for, there was still a ~ 5% sex difference in peak V̇O₂ V˙O2 . SV max made a modest additional contribution to explain the development of peak V̇O₂ , V˙O2, but there remained an unresolved sex difference of ~ 4%.