Repeatability of peak oxygen uptake in children who are healthy

This study was designed to determine test-retest repeatability of variables during a maximal cardiopulmonary exercise test (CPET) in children, and to report repeatability coefficients using limits of agreement analysis. This method of analysis is recommended for valid interpretation of outcome measures used in clinical or research interventions, and has not been reported in previous studies of peak oxygen uptake (VO2peak) in children.

Two exercise tests were performed three to seven days apart in nine healthy children aged eight to 11 years, using a treadmill protocol. Limits of agreement analyses were performed, with bias (mean difference test 2 - test 1) and coefficients of repeatability (2 standard deviations [SD] of difference) calculated for VO2peak, peak heart rate (HRpeak) and peak minute ventilation (VEpeak).

No significant differences were found between test and retest scores for any variable. VO2peak data demonstrated a bias of 1.4 ml kg/min with repeatability coefficient of 4.4 ml kg/min. The range described by 95% limits of agreement for VO2peak was -3 to + 5 ml kg/min. Bias and 95% limits of agreement for VEpeak and HRpeak were similarly described.

The 95% limits of agreement for VO2peak imply that on repeated testing, a reduction of 3 or increase of 5.8 ml kg/min is likely to be clinically significant. This study provides reference values for repeatability of key variables during CPET in healthy children that should be considered when interpreting results from repeated testing.