Are there Differences between Adolescent Males and Females for Maintaining the Metabolic Cost at Maximal Oxygen Uptake?

Abstract

Purpose: The present study looked at gender difference in oxygen delivery-extraction at maximal oxygen uptake in healthy adolescents. Methods: 36 adolescent males (14.9 ± 1.1 years) and 33 adolescent females (15.0 ± 1.1 years) underwent a maximal oxygen uptake test and a two dimensional direct m-mode echocardiography performed on a bicycle ergometry. Arteriovenous oxygen difference was defined by utilizing the Fick equation. Results: At rest, males compared to females had significantly (p<0.05) higher oxygen extraction (38.8 ± 1.4 and 31.8 ± 1.2 mL.kg-1 .min-1 respectively), systolic blood pressure, and mean arterial blood pressure. At peak exercise test, males compared to females demonstrated significant (P<0.05) higher values for cardiac output (16.6 ± 0.7 and 15.4 ± 0.6 L∙min-1 respectively), stroke volume (83.9 ± 5.1 and 78.5 ± 4.6 mL respectively), oxygen uptake (47.3 ± 3.7 and 39.6 ± 1.1 mL∙kg-1∙min-1, respectivel y), while oxygen extraction was significantly higher in females compared to males (123.6 ± 7.6 and 115.5 ± 5.4 mL∙L-1 respectively). Conclusions: This study suggests that normal adolescents; male and females respond to the maximal oxygen uptake test by increased their left ventricular systolic function, however, it was less augmented in the females due to gender and energy metabolism differences. Consequently, females increased their oxygen extraction more than the males as a compensation for the lower cardiac output and hence, lower oxygen delivery.