Aim: To study test–retest reliability of physiological cost index (PCI) and total cost index (TCI) in three groups of children. TCI modified PCI by excluding rest heart rate in calculation.
Methods: Energy cost was evaluated from two consecutive walking tests, and results were compared between methods, tests and groups. Thirty-nine children, eight with cerebral palsy, 11 with cystic fibrosis and 20 healthy controls, aged 5–16 years participated in the study conducted at the Clinical Nutrition and Metabolism laboratory, University Hospital, Uppsala, Sweden. Heart rate was recorded during sitting and walking at self-selected speed. PCI and TCI were calculated using both non-steady-state and steady-state work heart rates. Test–retest reliability was analysed by mean of differences, pooled SD, coefficient of variation (CV%) and correlation coefficients.
Results: Reliability was high for PCI and TCI. TCI showed consistently lower variation between tests than PCI for all groups. In the group with cerebral palsy, using non-steady-state showed highest reliability.
Conclusion: Both PCI and TCI were reliable methods when calculating energy cost in children with cerebral palsy, cystic fibrosis and controls. TCI seemed to be a suitable alternative in the evaluation of gait efficiency in children.