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

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].

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].

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].

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%.