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 (V ˙ O 2). Methods: The peak V ˙ O 2 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 V ˙ O 2 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 V ˙ O 2. Results: Progressive increases in treadmill running speed resulted in significant (p < 0.01) increases in V ˙ O 2, 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 V ˙ O 2 increased with FFM but after adjusting for FFM0.98, a significant (p < 0.05) sex difference in peak V ˙ O 2 remained. Introducing SVmax to the multilevel model revealed a significant (p < 0.05), but small additional effect of SVmax on peak V ˙ O 2. Conclusions: Fat-free mass explained sex differences in SVmax, but with FFM controlled for, there was still a ~ 5% sex difference in peak V ˙ O 2. SVmax made a modest additional contribution to explain the development of peak V ˙ O 2, but there remained an unresolved sex difference of ~ 4%.