Maximal oxygen uptake (V˙O2max) in females, expressed as ml × kg-1 × min-1, declines steadily during the first three decades of life. The contribution of diminished cardiovascular function to this apparent fall in aerobic fitness is unknown. Cardiac responses to maximal cycle exercise were compared in 24 premenarcheal females (mean age 11.7 years) and 17 young adult women (mean age 27.4 years) using Doppler echocardiography. Mean V˙O2max was 40 ml × kg-1 × min-1 and 34.7 ml × kg-1 × min-1 in the girls and women, respectively (p < 0.05). When V˙O2max was expressed relative to allometrically-derived mass0.52, however, no significant difference was observed in aerobic fitness between the two groups. Similar allometric analyses revealed no significant differences in average maximal cardiac output (10.50 vs 10.07 L × min-1 BSA-1.11 for girls and women, respectively) nor maximal stroke volume (53 vs 56 ml BSA-1.13 respectively). These findings suggest that 1) allometric scaling is important in eliminating the effects of body size on V˙O2max, 2) body dimension differences can account for variations in V˙O2 in young females, and 3) cardiac functional reserve is similar in premenarcheal girls and young adult women.
Key words:
Children - fitness - oxygen uptake - cardiac output
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D. M. Thomas Rowland
Department of Pediatrics Baystate Medical Center
Springfield, MA 01199
USA
Phone: + 1 (413) 7947350
Fax: + 1 (413) 7943623
Email: thomas.rowland@bhs.org
