Multilevel allometric modelling of maximal stroke volume and peak oxygen uptake in 11\u201313-year-olds

Abstract

PurposeTo 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 left( {{dot{text{V}}text{O}}_{2} } right) .MethodsThe peak {dot{text{V}}text{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 {dot{text{V}}text{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 {dot{text{V}}text{O}}_{2} .ResultsProgressive increases in treadmill running speed resulted in significant (p < 0.01) increases in {dot{text{V}}text{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 {dot{text{V}}text{O}}_{2} increased with FFM but after adjusting for FFM0.98, a significant (p < 0.05) sex difference in peak {dot{text{V}}text{O}}_{2} remained. Introducing SVmax to the multilevel model revealed a significant (p < 0.05), but small additional effect of SVmax on peak {dot{text{V}}text{O}}_{2} .ConclusionsFat-free mass explained sex differences in SVmax, but with FFM controlled for, there was still a ~ 5% sex difference in peak {dot{text{V}}text{O}}_{2} . SVmax made a modest additional contribution to explain the development of peak {dot{text{V}}text{O}}_{2} , but there remained an unresolved sex difference of ~ 4%.