Submaximal Step-Testing as a Tool to Assess Cardiovascular Fitness in Youth Who Are Obese

Abstract

INTRODUCTION: Youth who are obese typically have lower cardiovascular fitness levels than their normal weight peers. The greater amount of body fat for children who are obese coupled with a generally decreased amount of physical activity oftentimes limits their ability to reach true maximal values during maximal exercise testing. Submaximal testing was therefore evaluated as a novel tool to better assess cardiovascular fitness among children who are obese. PURPOSE:To use submaximal testing to measure changes in cardiovascular fitness in youth who are obese following METHODS:This pilot study was comprised of a subsample of children who were obese and consecutively enrolled in Healthy Kids, Healthy Weight, a weight management program at Rainbow Babies & Children's Hospital in Cleveland, Ohio. The participants were 29 children between the ages of 7 to 18 years (13 males, 16 females). The submaximal test was performed at the initial fitness visit and again on the last night of the 12-week intervention. Each child performed the 3-minute YMCA step-test. The child stepped up and down on a 30cm bench for 3 minutes at a cadence of 96 beats per minute, set by metronome. Within 5 seconds following the last beat, the child was seated and heart rate was palpated for 60 seconds via radial pulse. The number of beats per minute (BPM) was recorded. RESULTS:BPM decreased significantly from baseline to end of intervention (112.3 bpm vs. 106.0 bpm; p=0.02) as did BMI (p=0.02) and BMI z-score (p=0.006). Change in cardiovascular fitness, as measured by change in BPM, was significantly associated with baseline heart rate (r=-.53, p=0.003); the higher the baseline BPM, the greater the decrease was from baseline to end of intervention. There were no significant associations between BPM change and age, gender, or baseline BMI or BMI z-score change. CONCLUSIONS: Submaximal step testing may be a useful tool for determining changes in cardiovascular fitness among treatment-seeking children who are obese. Cardiovascular fitness, BMI, and BMI z-score change in these children significantly improved following a 12-week, multi-disciplinary intervention, with greatest improvements in BPM among children with lowest cardiovascular fitness at baseline.