The clinical relevance of selecting resting data at different points in an energy cost of walking test in cerebral palsy

Aim: Energy cost of walking (ECOW) is defined as 'walking oxygen consumption minus resting oxygen consumption divided by speed', where 'resting' data can be obtained either at the start or cessation of a test. This study aimed to ascertain when resting data should be taken during an ECOW test in children with cerebral palsy (CP).

Method: Resting oxygen consumption per unit mass (VO(2) ) and heart rate were recorded in children without physical impairment (18 males, 13 females; mean age 11 y [SD 2 y 1 mo]) and children with diplegic CP (18 males, 13 females; mean age 11 y [SD 2 y 6 mo, Gross Motor Function Classification System levels I and II]) at three stages, namely pre- and posttest sitting and pretest standing before and after an 8-minute ECOW test using the Cosmed K4b.

Results: Heart rate and VO(2) differed significantly between groups and stages (p ≤ 0.05) except for heart rate in standing and posttest sitting in the unimpaired children and for VO(2) during pretest sitting between groups. These differences impacted on the calculation of non-dimensional net oxygen cost (NDNOC) and physiological cost index (PCI) in CP but not in the unimpaired group. PCI was correlated with NDNOC in CP but not in the unimpaired cohort.

Interpretation: Pretest sitting resting data appear to be the most appropriate for use in the calculation of NDNOC and PCI. PCI may still have relevance in pathology where walking efficiency is compromised.