Allometric Association between Six-Minute Walk Distance and Both Body Size and Shape in Young Obese Girls.

BACKGROUND

The 6-min walk test (6MWT) provides information regarding functional capacity, response to therapy and prognosis in a variety of chronic cardiovascular disorders. Variability in body size and composition, particularly in obese people, confounds the six-minute covered distance (6MWD). The aim of the present study was to adopt allometric models to identify the most appropriate body size/shape; i.e., body mass (BM), body height (BH), body mass index (BMI) and estimated fat-free mass (FFM); associated with the 6MWD in 190 young girls with obesity.

METHODS

Nonlinear allometric modeling was used to calculate common body size exponents for BM, BH, BMI and FFM. In a validation sample of 35 age-matched obese girls, these allometric exponents were used prospectively.

RESULTS

The point estimates for the size exponents (95% confidence interval) from the separate allometric models were: BM 0.23 (0.19-0.27), BH 0.91 (0.78-1.03), BMI 0.33 (0.23-0.44) and FFM 0.28 (0.24-0.33). The presence of significant residual size correlations for 6MWD/BH indicates that the influence of body size was not correctly partitioned out. In the validation group, the correlations between 6MWD BM and BM, 6MWD BMI and BMI, and 6MWD FFM and FFM using the established exponents were not statistically different from zero (r = 0.01), implying that participants in the allometric investigation were not penalized based on their BM, BMI, or FFM.

CONCLUSION

We conclude that BM, BMI, BH and FFM, as indicators of body size/shape, are the most valid allometric denominators for the scaling of 6MWD in a group of young girls with obesity.