Measurement of Energy Cost by the Physiological Cost Index in Walking After Stroke

Danielsson A, Willén C, Sunnerhagen KS. Measurement of energy cost by the Physiological Cost Index in walking after stroke.ObjectiveTo compare the Physiological Cost Index (PCI) with direct measurement of oxygen consumption (V̇o2) as an estimate of energy cost in persons with stroke and healthy subjects.DesignTest-retest on separate days. A comparison of 2 methods of measurement. Measurements with and without an orthosis.SettingA university hospital.ParticipantsA convenience sample of 20 persons with hemiparesis more than 6 months after stroke and 16 healthy subjects, ages 30 to 63 years.InterventionsFive minutes of treadmill walking at self-selected speeds while recording V̇o2 levels and heart rates. Additional data was recorded for 11 of the stroke subjects with and without an ankle-foot orthosis.Main Outcome MeasuresV̇o2 and the PCI.ResultsNo significant differences were found in the PCI or V̇o2 between test and retest. Both PCI and V̇o2 per distance were higher for the stroke subjects compared with healthy subjects. PCI showed a larger dispersion than V̇o2 between test and retest. The regression analysis for PCI showed that the model including age, sex, group assignment, and V̇o2 could explain 53% of the variation. The PCI did not show a significant difference in walking with or without an orthosis, whereas V̇o2 differed significantly.ConclusionsThe PCI showed limited reliability and validity as a measure of energy cost after stroke due to the extensive variability between test and retest.