Reliability of energy cost calculations in children with cerebral palsy, cystic fibrosis and healthy controls

Abstract

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. © 2011 The Author(s)/Acta Pædiatrica.