Reliability of a progressive maximal cycle ergometer test to assess peak oxygen uptake in children with mild to moderate cerebral palsy

Rehabilitation research in children with cerebral palsy (CP) is increasingly addressing cardiorespiratory fitness testing. However, evidence on the reliability of peak oxygen uptake (Vo2peak) measurements, considered the best indicator of aerobic fitness, is not available in this population. The objective of this study was to establish the reliability of a progressive maximal cycle ergometer test when assessing Vo2peak in children with mild to moderate CP. Repeated measures were used to assess test-retest reliability. Eligible participants were ambulant, 6 to 14 years of age, and classified as level I, II, or III according to the Gross Motor Function Classification System (GMFCS). Two progressive maximal cycle ergometer tests were conducted (separated by 3 weeks), with the workload increasing every minute in steps of 3 to 11 W, dependent on height and GMFCS level. Reliability was determined by means of the intraclass correlation coefficient (ICC [2,1]) and smallest detectable change (SDC). Twenty-one children participated (GMFCS I: n=4; GMFCS II: n=12; and GMFCS III: n=5). Sixteen of them (9 boys, 7 girls; GMFCS I: n=3; GMFCS II: n=11; and GMFCS III: n=2) performed 2 successful tests, separated by 9.5 days on average. Reliability for Vo2peak was excellent (ICC=.94, 95% confidence interval=.83-.98). The SDC was 5.72 mL/kg/min, reflecting 14.6% of the mean. The small sample size did not allow separate analysis of reliability per GMFCS level. In children with CP of GMFCS levels I and II, a progressive maximal cycle ergometer test to assess Vo2peak is reliable and has the potential to detect change in cardiorespiratory fitness over time. Further study is needed to establish the reliability of Vo2peak in children of GMFCS level III