INTRASPECIFIC ALLOMETRY OF AEROBIC PERFORMANCE IN PREPUBESCENT CHILDREN611

Abstract

The principles of allometry provide statistically and biologically valid techniques with which to normalise physiological data for body size differences. Little is known however, about the influence of gender and body composition on power function exponents for physiological variables in children. The purpose of this study therefore was to examine the allometric relationships between body size variables [body mass (BM), fat free mass(FFM), and height (H)], and peak ˙VO2 in prepubertal children (16 females and 14 males, mean age 10.5 ± 0.7 years, of equivalent Tanner maturational stage). Peak ˙VO2 was determined via indirect calorimetry during an incremental cycle ergometer test, with Slaughter skinfold equations adopted to estimate percent fat and FFM. Multivariate allometric scaling (MAS) was employed to compute power functions of the form˙VO2 peak = a. GENDERc. BMb (or FFMb or Hb). This procedure controls for the possible confounding influence of gender in combining the samples, and provides a common, `best compromise'b exponent Peak ˙VO2 was found to be proportional to BM0.66 ± 0.13, FFM1.03 ± 0.1, and H1.82± 0.5 (95% CI). The BM and H exponents conform closely to the predictions of the theory of geometric similarity - ˙VO2 proportional to mass raised to the 2/3 power, or to the square of stature. For each of the above exponents, correlations between scaled oxygen uptake data(˙VO2 peak/xb) and the specific body size variable (x) were not different from zero (P > 0.05). The results indicate that the MAS was successful in providing scaled physiological indices free from the influence of body size. However, allometric regressions are sample specific and empirically determined, and should not be extrapolated beyond the body size range represented by the actual data.