Scaling Vo(2) peak in obese and non-obese girls

Objective: The conventional ratio method (milliliters O-2 per mass) typical ly is used to express Vo(2) peak. The goal of the current study was to comp are Vo(2) peak of obese girls with normal-weight girls by ratio and allomet ric scaling methods. Research Methods and Procedures: We compared Vo(2) peak by ratio and allome tric methods in 46 obese and 47 normal-weight girls. Indirect calorimetry w as used to measure Vo(2) peak during either treadmill running or walking. R egression analysis was used to determine coefficients for mass and stature for each group with ANOVA used to compare data between groups. Results: The obese girls were taller and had higher values of body fatness (p less than or equal to 0.05). Absolute Vo(2) peak (liters per minute) was similar between groups; however Vo(2) peak relative to mass was 50% lower (p less than or equal to 0.05) in the obese girls. When Vo(2) peak (millili ters per minute per kilogram) and mass were correlated, r = -0.48 was found in the obese group. Allometric scaling of logarithmic transformed stature and mass reduced this to r = -0.002, thus eliminating the bias associated w ith the ratio method. Adjusting Vo(2) peak allometrically scaled for mass, stature, and the combination of mass and stature reduced the difference bet ween groups from 50% (ratio method) to 10% to 11% (p < 0.05) with higher va lues found in the normal-weight girls. Discussion: These results demonstrate the bias associated with the ratio me thod when comparing Vo(2) peak in obese girls with Vo(2) peak in normal-wei ght girls. Allometric scaling eliminated the bias and thus may reflect a tr uer comparative response.