Scaling physiological measurements for individuals of different body size

Abstract

Summary. This paper examines how selected physiological performance variables, such as maximal oxygen uptake, strength and power, might best be scaled for subject differences in body size. The apparent dilemma between using either ratio standards or a linear adjustment method to scale was investigated by considering how maximal oxygen uptake (l" rain-1), peak and mean power output (W) might best be adjusted for differences in body mass (kg). A curvilinear power function model was shown to be theoretically, physiologically and empirically superior to the linear models. Based on the fitted power functions, the best method of scaling maximum oxygen uptake, peak and mean power output, required these variables to be divided by body mass, recorded in the units kg 2/3. Hence, the power function ratio standards (ml.kg -2/3.min -1) and (W.kg-2/3) were best able to describe a wide range of subjects in terms of their physiological capacity, i.e. their ability to utilise oxygen or record power maximally, independent of body size. The simple ratio standards (ml. kg-1. min-1) and (W. kg -1) were found to best describe the same subjects according to their performance capacities or ability to run which are highly dependent on body size. The appropriate model to explain the experimental design effects on such ratio standards was shown to be log-normal rather than normal. Simply by taking logarithms of the power function ratio standard, identical solutions for the design effects are obtained using either ANOVA or, by taking the unscaled physiological variable as the dependent variable and the body size variable as the covariate, ANCOVA methods.

Morphological dependency of cutaneous blood flow and sweating during compensable heat stress when heat-loss requirements are matched across participants

“…Expired respiratory gases and volumes were used to derive peak oxygen consumption (TrueOne 2400; ParvoMedics, Sandy, UT). Because those values have an allometric relationship with body mass (28,37), data were expressed per unit body mass raised to the exponent of 0.87 (ml·kg Ϫ0.87 ·min Ϫ1 ) (45) to avoid the size bias introduced with arithmetic normalization (28).…”

“…Wholebody sweat rate is often normalized to the body surface area to minimize interindividual variability. However, this can introduce a bias when that relationship varies significantly from linearity, or it does not pass through zero (28,35). Because the relationship between whole body sweat rate and surface area did not satisfy those criteria, individual sweat rates were normalized using the adjusted regression analysis technique (after 45).…”

Total body fat does not influence maximal aerobic capacity

“…15,32 ± 40 Historically, VO 2max has been adjusted using ratio scaling that makes the assumption that, once VO 2max has been divided by body weight, any difference in VO 2 due to body weight is removed. 36 Much dialogue has occurred with the expression of VO 2 as a ratio of body weight. 33,34,36,39,41 In part this is due to the negative correlation between body weight and VO 2 per unit of body weight.…”

“…36 Much dialogue has occurred with the expression of VO 2 as a ratio of body weight. 33,34,36,39,41 In part this is due to the negative correlation between body weight and VO 2 per unit of body weight. 35,36 This relationship gives the misleading impression that heavier persons have a relatively lower oxygen uptake and hence, low aerobic capacity.…”

Variabilidade Do Desempenho No Line-Drill Test Em Adolescentes Jogadores De Basquetebol

“…Adicionalmente foi verificada a assunção de homogeneidade dos resíduos dos modelos alométricos proporcionais. Os modelos alométricos consideram-se válidos para controlar os efeitos do tamanho corporal e maturação somática se a correlação entre os resíduos dos modelos e o indicador de maturação e a respectiva variável de dimensão corporal, separadamente, se aproximar de zero 12 . Os parâmetros desconhecidos e os respectivos intervalos de confiança a 95% nos modelos alométricos foram estimados pelo método de máxima verossimilhança.…”