Measurement of energy cost by the physiological cost index in walking after stroke

Abstract

Objective: To compare the Physiological Cost Index (PCI) with direct measurement of oxygen consumption (Vo(2)) as an estimate of energy cost in persons with stroke and healthy subjects.

Design: Test-retest on separate days. A comparison of 2 methods of measurement. Measurements with and without an orthosis.

Setting: A university hospital.

Participants: A convenience sample of 20 persons with hemiparesis more than 6 months after stroke and 16 healthy subjects, ages 30 to 63 years.

Interventions: Five minutes of treadmill walking at self-selected speeds while recording Vo(2) levels and heart rates. Additional data was recorded for 11 of the stroke subjects with and without an ankle-foot orthosis.

Main outcome measures: Vo(2) and the PCI.

Results: No significant differences were found in the PCI or Vo(2) between test and retest. Both PCI and Vo(2) per distance were higher for the stroke subjects compared with healthy subjects. PCI showed a larger dispersion than Vo(2) between test and retest. The regression analysis for PCI showed that the model including age, sex, group assignment, and Vo(2) could explain 53% of the variation. The PCI did not show a significant difference in walking with or without an orthosis, whereas Vo(2) differed significantly.

Conclusions: The PCI showed limited reliability and validity as a measure of energy cost after stroke due to the extensive variability between test and retest.