Allometric scaling for normalizing maximal oxygen uptake in elite rugby union players

Introduction: The relation of a biological variable to body mass is typically characterized by an allometric scaling law. The purpose of this study was to evaluate the relationship between oxygen consumption (VO2max), as a parameter of aerobic exercise performance, and body composition in rugby players. Material and method: The sample included one hundred and seven males of the Spanish rugby team. Age: 25.1 ± 3.4 years; body mass (BM): 89.8 ± 11.7 kg, height: 182.4 ± 6.5 cm; 52 backs (BR) and 55 forwards (FR). Maximum oxygen consumption (VO2max, l.min-1) was measured during treadmill exercise test with progressive workload. Anthropometrical measurements were performed to estimate the fat-free mass (FFM) and muscle mass (MM). The allometric exponent “b” was determined from equation y = a * xb; where “y” is VO2max and, “x” is the corresponding mass (BM, FFM or MM) and “a” is one constant. Results: The VO2max was 4.87 ± 0.56 l.min-1, BR vs FR, 4.67 ± 0.48 l.min-1 vs 5.06 ± 0.06 l.min-1; FFM: 77.5±7.7 kg, 73.5±7 kg vs 81.3±6.3 kg; and MM: 52.9±6.5 kg, 49.6±5.6 kg vs 56.1±5.8 kg. The allometric exponents (p <0.0001; R2 = 0.4) were: 0.58 for BM (95% CI: 0.45 - 0.72); 0.71 for FFM (95% CI: 0.53 - 0.90); and 0.58 for MM (95% CI: 0.43 - 0.73). Significant differences (p <0.0001) were found BR vs FR according to their anthropometric characteristics and VO2max with respect to BM and MM without allometric scaling. While the VO2max indexed by means of allometric scaling was similar between BR and FR. Conclusions: In comparative studies, the VO2max should be expressed proportional to the 0.58 power of body mass or related to FFM in order to take into account the variability in of body composition in rugby players.