Background Peak oxygen consumption (peak •) has been used to measure the highest oxygen consumption in healthy children and adolescents because of the difficulty in demonstrating a plateau in • VO2 during treadmill exercise in children as maximal tests are stopped by voluntary exhaustion. Cross-sectional studies have shown that peak • VO2, expressed relative to body mass, is greater in boys than in girls. However, in both sexes there is a positive correlation between body mass index (BMI) and peak • VO2.
Objectives To assess the relationship between BMI and peak • VO2 in overweight children.
Methods, Subjects, and Procedures A pilot study with ten patients referred to our Risk Factor Reduction Program between February 2004 and April 2004 was undertaken. All patients had BMI ≥ 95th percentile. Patients did not have any significant cardiovascular disease or other co-morbidities that precluded them from exercising. All subjects underwent a Bruce protocol treadmill test (TM); TM was stopped at the level of maximal voluntary effort. Standard 12-lead EKG was performed, and Peak • VO2 was measured with Vacu-Med mini-CPX, (± 3% accuracy). Peak • VO2 was assumed when respiratory quotient was ≥ 1.1 and heart rate reaches 90% of maximum heart rate.
Results Five females and five males were included. Mean age: 13.3 years (range: 10 – 16 years), 70% were Caucasian and 30% Hispanic. Mean BMI: 37.2 (SD: 8.1). Mean BMI Z-score: +2.45 (SD: 0.34). Mean peak • VO2: 26.7 ml/kg (SD: 4.32 ml/kg). A negative correlation were found between BMI and peak • VO2 (r = -0.71, p-value = 0.02). There were no differences of mean peak • VO2 between sexes.
Conclusions Peak oxygen consumption correlated negatively with BMI in this group of obese patients. Peak • VO2 did not show differences between boys and girls. These finding differs from published reports on non-obese children, possibly due to the fact that the equation to calculate • VO2 consumption does not take into account the individual’s body composition.