Monitoring Exercise in Children and Adolescents With Cystic Fibrosis: Validation of the CSA Accelerometer

We examined the ability of the Computer Science Applications (CSA) accelerometer to predict energy expenditure during treadmill walking and stair stepping in nine children and adolescents with cystic fibrosis (CF) (mean age 12.1 yr, SD + 2.8) and ten healthy controls (mean age 10.8 yr. SD + 2.2). The accelerometer was attached above the hip and interfaced with a heart rate monitor worn on the chest. Oxygen uptake (VO₂) was simultaneously measured using a MedGraphics metabolic cart. The subjects walked at speeds ranging from 2.0 to 4.5 mi·hr^-1 and stepped on 4 and 8 inch blocks at cadences of 100 and 120 beats·minute^-1. For subjects with CE, the average validity correlation between accelerometry and VO₂ was 0.84 for treadmill walking and 0.97 for stair stepping. Using linear regression, accelerometry explained 62% of the variability in VO₂ during walking and 87% during stair stepping. Standard errors of the estimate for predicting VO₂ using accelerometry ranged from 16.8 to 16Z2 m102.min’. Results for the control group were similar and there were no statistical between-group differences in physiological responses or accelerometry values. Our data demonstrate the validity of the CSA accelerometer for estimating VO₂ in children and adolescents with CF during treadmill walking and stair stepping. Findings suggest that accelerometry holds promise as an objective exercise monitor for pediatric patients with CF.