Peak Oxygen Consumption During Exercise In Obese Children.

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.