Sex differences in response to maximal exercise stress test in trained adolescents

A total of 24 adolescent females and 27 adolescent males aged 13–19？years underwent a maximal bicycle exercise stress test with measurement of cardiovascular variables, cardiac output, lung volumes, metabolic factors/lactate concentrations and breath-by-breath monitoring of ventilation, and determination of peak VO2.Maximum heart rate was similar in females (191？±？9？bpm) and males (194？±？7？bpm), cardiac index at maximum exercise was lower in females (7.0？±？1.0？l/min/m2) than in males (8.3？±？1.4？l/min/m2, P？<？0.05). Metabolic responses and RQ at maximum exercise were similar (females: 1.04？±？0.06 vs. males: 1.05？±？0.05). Peak VO2 was lower in females (2.37？±？0.34？l/min) than in males (3.38？±？0.49？l/min, P？<？0.05). When peak VO2 was normalized to leg muscle mass sex differences disappeared (females: 161？±？21？ml/min/kg vs. males: 170？±？23？ml/min/kg). The increase in cardiac index during exercise is the key factor responsible for the greater peak VO2 in adolescent boys compared to girls.Differences in peak VO2 in adolescent boys and girls disappear when peak VO2 is normalized to estimated leg muscle mass and therefore provide a tool to conduct individual and intersex comparisons of fitness when evaluating adolescent athletes in aerobic sports.Physical activity and training is important for initiating and sustaining cardiovascular health. As such, encouragement from childhood and the possibility to participate in sports activity is a major health issue which must be sustained. Reaching adolescence, however, increasing expectations and competitive demands have gradually emerged as an important aspect of recreational sports in the young. During the past decades there has been a gradual increase in the number of teenagers participating in competitive sports and the number of female athletes has increased in aerobic team sports [1,2] – in Sweden in particular in soccer, floor-ball and ice-hockey [3]. Correct and adequate planning of physical and exercise training is instrume