Maximal oxygen uptake in children of different body mass : should maximal oxygen uptake be expressed differently for children of different body mass?

Abstract

Background: Maximal oxygen uptake ( V O2max ) has important implications for current and future health in children. There is ongoing debate on how to express V O2max in children and adolescents. Objectives: Are scaling factors different in obese and normal weight children and between genders? How does percentage fat influence aerobic fitness? Methods: 57 obese (30 girls) and 79 children of normal weight (38girls) in the age 7-17 years were include in the present study. V O2max were measured during a treadmill running test, were both the incline and speed increased until subjects were exhausted. Body compositions were measured with dual-energy X-ray absorptiometry (DXA) or a Harpenden fat caliper. Allometric scaling factors were calculated using linear regression of log-transformed data. Results: Allometric scaling factors were 0.51 for obese girls, 0.53 for normal weight girls, 0.47 for obese boys and 0.27 for normal weight boys. Obese boys had almost the same allometric scaling factor (0.47) as girls, and normal weight boys (0.27) had the lowest scaling factor of all subjects. Conclusion: findings in the present study demonstrate that use of mass exponent when comparing V O2max in obese and normal weight children. It seems that percentage fat doesn't have a great influence on children's V O2max . The difference between obese and normal weight children has to be due to other factors than percentage fat.