Scaling peak Vo(2) to body mass in young male and female distance runners

This study examined age- and sex-associated variation in peak oxygen consum ption ((V) over dot O-2) of young male and female distance runners from an allometric scaling perspective. Subjects were from two separate studies of 9- to 19-yr-old distance runners from the mid-Michigan area, one conducted between 1982 and 1986 (Young Runners Study I, YRS I) and the other in 1999- 2000 (Young Runners Study II, YRS II). Data from 27 boys and 27 girls from YRS I and 48 boys and 22 girls from the YRS II were included, and a total o f 139 and 108 measurements of body size and peak (V) over dot O-2 in boys a nd girls, respectively, were available. Subjects were divided into whole ye ar age groups. A 2 x 9 (sex x age group) ANOVA was used to examine differen ces in peak (V) over dot O-2. Intraindividual ontogenetic allometric scalin g was determined in 20 boys and 17 girls measured annually for 3-5 yr. Allo metric scaling factors were calculated using linear regression of log-trans formed data. Results indicated that 1) absolute peak (V) over dot O-2 incre ases with age in boys and girls, 2) relative peak (V) over dot O-2 (ml.kg(- 1).min(-)1) remains relatively stable in boys and in girls, 3) relative pea k (V) over dot O-2 (ml.kg(-0.75).min(-1)) increases throughout the age rang e in boys and increases in girls until age 15 yr, and 4) peak (V) over dot O-2 adjusted for body mass (ml/min) increases with age in boys and girls. T he overall mean cross-sectional scaling factor was 1.01 +/- 0.03 (SE) in bo ys and 0.85 +/- 0.05 (SE) in girls. Significant age 3 sex interactions and significant scaling factors between sexes identify the progressive divergen ce of peak (V) over dot O-2 between adolescent male and female distance run ners. Mean ontogenetic allometric scaling factors were 0.81 [0.71- 0.92, 95 % confidence interval (CI)] and 0.61 (0.50- 0.72, 95% CI) in boys and girls , respectively (P = 0.002). There was considerable variation in individual scaling factors (0.51- 1.31 and 0.28-0.90 in boys and girls, respectively). The results suggest that the interpretation of growth-related changes in p eak (V) over dot O-2 of young distance runners is dependent upon the manner of expressing peak (V) over dot O-2 relative to body size and/or the stati stical technique employed.