Baseline Fitness Measures In A Cohort Of Obese Children

Abstract

BACKGROUND: There is an increasing population of overweight and obese children. While many studies have investigated interventional strategies to reduce weight, few studies have reported the actual fitness status of obese children. PURPOSE: To establish baseline fitness measures in a mixed-race cohort of obese children. METHODS: We studied 33 patients (18 male) between the ages of 10-17 years. Patients were referred to the Children's Heart Centre from the Centre for Healthy Weights Program at B.C. Children's Hospital. All patients were above the 95th percentile for body mass index (BMI), adjusted for age. Initial assessment included a physical examination by a pediatric cardiologist, an electrocardiogram (ECG), an echocardiogram (ECHO), and a cardiopulmonary exercise test (CPX). The CPX was completed on a treadmill according to our institutional protocol. Treadmill speed started at 2.0 mph and increased by 0.5 mph every minute until volitional fatigue. Measurements included: height, weight, calculated body surface area (BSA) and BMI, minute ventilation (VE), peak oxygen consumption (VO2peak), respiratory exchange ratio (RER) and heart rate (HR). Our criteria for a maximal test were a HR ≥180 bpm and a RER ≥1.10. RESULTS: Mean height and weight were 164.9 ± 10.5 cm and 94.4 ± 16.8 kg, respectively. ECG and ECHO findings were normal in all but 1 patient who had an enlarged left ventricle. Only 14/33 (42%) patients satisfied the criteria for a maximal test. Peak VE was 83.0 ± 26.6 L/min. Mean absolute VO2peak was 2.70 ± 0.60 L/ min. Mean relative VO2peak was 29.0 ± 6.5 ml/kg/min (64% predicted). There was no significant difference between relative VO2peak for boys and girls. There was a significant correlation between HR and absolute VO2peak (r=0.46; p<0.01). CONCLUSION: We have shown that in this cohort of mixed-race obese children, less than half were able to satisfy our criteria for completing a maximal effort exercise test. In those patients it is difficult to determine whether or not there is a significant reduction in their aerobic capacity, interpret other aspects of their test results, and provide objective information for exercise prescription. Exercise testing is safe and should be considered before providing exercise prescription to these children.