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 [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 SV(max) 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 SV(max), 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 FFM(0.72) 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 FFM(0.98), a significant (p < 0.05) sex difference in peak [Formula: see text] remained. Introducing SV(max) 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 SV(max), but with FFM controlled for, there was still a ~ 5% sex difference in peak [Formula: see text] . SV(max) made a modest additional contribution to explain the development of peak [Formula: see text] but there remained an unresolved sex difference of ~ 4%.