Applicability of an allometric power equation to children, adolescents and young adults of extreme body size

Aim. 
The aim of this study was to assess the applicability of a regression model for peak power (PP) and total mechanical work (TMW) for healthy children, adolescents and young adults especially in the extreme ranges of stature, mass, and body mass index (BMI).
Methods. 
A total of 454 children, adolescents and young adults aged 6-20 years volunteered for the study. Subjects, whose stature, mass and BMI were between the 10th and the 90th centile, were selected to calculate the prediction equation: 267 subjects fulfilled these criteria. Each subject performed two unilateral Wingate tests (ULWAnT), one with each leg. PP (Watts) and TMW (Joules) of the left and right leg were averaged for each individual. Ln(mass), in(stature), age, age2, gender, and age × gender were used as predictors for in(PP) and ln(TMW). The applicability of the prediction equation was tested on individuals who were less than the 10th centile or greater than the 90th centile for stature, body mass and BMI.
Results.
All independent variables were statistically significant (P<0.05) predictors of in(PP), adjusted R2=0.93 and all but gender were significant predictors for in(TMW), adjusted R2=0.95. However, measured in(PP) and in(TMW) were significantly lower than predicted in(PP) and in(TMW) for subjects >90th centile for stature, body mass, or BMI.Conclusion. the prediction equations overestimated PP and TMW in children, adolescents and young adults who were heavier than the reference subjects, as indicated by a relatively high body mass or high BMI for age or were taller than the reference subjects. The findings might reflect a deficit in anaerobic capacity in children, adolescents and young adults with relatively large body size for their age.