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Feasibility of the physiological cost index as an outcome measure for the assessment of energy expenditure during walking,☆☆,,★★,

https://doi.org/10.1053/apmr.2002.35655Get rights and content

Abstract

IJzerman MJ, Nene AV. Feasibility of the Physiological Cost Index as an outcome measure for the assessment of energy expenditure during walking. Arch Phys Med Rehabil 2002;83:1777-82. Objective: To determine if the Physiological Cost Index (PCI) can be recommended as an outcome measure in clinical trials. Design: Three assessments were performed, 2 with shoes, 1 without. The difference between walking with shoes and walking barefoot was used to study the ability of the PCI to detect a change in the criterion standard. Setting: A research department affiliated with a rehabilitation hospital in the Netherlands. Participants: Twelve children with cerebral palsy. Interventions: During the first and third assessments, the children walked with shoes. During the intermediate assessment, the children walked without shoes. Main Outcome Measures: Breath-by-breath oxygen uptake, heart rate (HR), and walking speed were measured at a self-selected comfortable speed. Oxygen cost (EO2) and the PCI were subsequently calculated offline. Feasibility judgments were made regarding the ability of the PCI to detect changes in a criterion standard and the statistical power of the outcome measure. Results: Pearson correlation coefficients were .66 and .62 for HRwalking−HRbaseline and HRwalking, respectively. The smallest detectable difference of the PCI and EO2 were 69% and 32%, respectively. A difference of at least 69% or 32% should be found before one can conclude a difference with a certainty of 95%. Conclusions: The reproducibility of the PCI and the ability to show small differences in EO2 were moderate. Subtracting HRbaseline when calculating the PCI is probably not useful because it only increased within-subject variability. With respect to statistical power of a new clinical trial, we recommend using EO2 instead of the PCI. © 2002 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation

Section snippets

Participants

Twelve children with CP participated in this study. Exclusion criteria were cardiovascular abnormalities, breathing difficulties, and surgery during the previous year. Eight children had hemiplegia and 4 had diplegia. The children were able to walk both barefoot and with shoes on for at least 10 minutes, with or without the use of a walker. All of these children understood the instructions given to them. Written permission from their parents to participate in this study was obtained. The local

Results

All subjects were able to walk at a comfortable speed with and without shoes for 8 minutes. During the first session, some children were anxious about wearing the facemask, but that improved during the second and the third sessions. All subjects were able to enter a steady state in approximately 4 minutes. The V̇O2 recording of 1 child during the first test was not reliable. We used the last recording (with shoes) as an estimate of walking with shoes instead.

Table 1 summarizes the crude data

Discussion

Although some articles have addressed the relation between heart rate and energy expenditure during walking, our study focused particularly on the feasibility of the PCI as an outcome measure in clinical trials. The PCI was considered feasible if the differences in energy requirements that have to be detected actually can be detected with sufficient statistical power. These topics are discussed later using our data, previously published data of a study in patients with SCI, and a literature

Conclusions

From the present study and a review of the literature, we concluded that reproducibility of the PCI and the ability to show small differences in EO2 is moderate. Subtracting HRbaseline when calculating the PCI is probably not useful because it does not improve the ability to detect differences, whereas it increases the within-subject variability. The calculated effect sizes were small, in particular because most of the differences in clinical trials were between 0% and 20%. If these small

Acknowledgements

We express our gratitude to Margit Schlecht, PT, Elles Stijnen, MSc, Miranda Velthuis, MSc, and Jans Ties, PT, for their valuable assistance and cooperation in the assessments.

References (28)

  • PO Astrand et al.

    Textbook of work physiology: physiological bases of exercise

    (1986)
  • MM Steven et al.

    The physiological cost of gait (PCG): a new technique for evaluating nonsteroidal anti-inflammatory drugs in rheumatoid arthritis

    Br J Rheumatol

    (1983)
  • AV Nene

    Physiological cost index of walking in able bodied adolescents and adults

    Clin Rehabil

    (1993)
  • P Butler et al.

    Physiological Cost Index of walking for normal children and its use as an indicator of physical handicap

    Dev Med Child Neurol

    (1984)
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    Reprint requests to Maarten J. IJzerman, PhD, Roessingh Research and Development, PO Box 310, 7500 AH Enschede, The Netherlands, e-mail: [email protected].

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