title: The use of the 6-min walk test as a proxy for the assessment of energy expenditure during gait in individuals with lower-limb amputation.
abstract: The objective of this study was to determine, and compare, the utility of the 6-min walk test (6 MWT) and self-selected walking speed over 15 m as proxies for the assessment of energy expenditure during gait in individuals with lower-limb amputation. Patients with unilateral, transfemoral amputation (n=6) and patients with unilateral, transtibial amputation (n=10) from community-based support groups participated in this study. Age-matched and body mass index-matched able-bodied controls (n=28) from a sample of convenience also participated. The main outcome measures were as follows: (a) distance, heart rate, oxygen consumption and oxygen cost during the 6 MWT and (b) self-selected walking speed over 15 m. Oxygen cost did not correlate significantly with self-selected walking speed over 15 m (ρ=-0.329) or average walking speed during the 6 MWT (ρ=-0.350). Significant correlations were not present between oxygen cost and the walking speed during the 6 MWT (range, ∣ρ∣: 0.210-0.531), although walking speeds at particular times of the 6 MWT demonstrated stronger correlations than others. Walking speed in the third min of walking during the 6 MWT recorded the strongest correlation with peak oxygen cost (ρ=-0.531). The 6 MWT is a submaximal measure in persons with lower-limb amputation. Self-selected walking speed over 15 m was not an appropriate proxy for the assessment of the energy cost of gait. Individuals with a lower-limb amputation require approximately 3 min of continuous walking to re-establish homoeostasis in heart rate, oxygen consumption and oxygen cost. The nonsignificant correlation between walking speeds during the 6 MWT and oxygen cost suggest that the 6 MWT can provide an indication of oxygen cost, but caution should be exercised when using it as a sole proxy for the measurement of oxygen cost in individuals with lower-limb amputation.
authors.affiliation: Graduate School of Biomedical Engineering, University of New South Wales, University of New South Wales, Australia.
authors.forename: Lauren
authors.initials: L
authors.lastname: Kark
authors.forename: Andrew S
authors.initials: AS
authors.lastname: McIntosh
authors.forename: Anne
authors.initials: A
authors.lastname: Simmons
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000671:Amputation, Surgical / Q000534:rehabilitation*; D004185:Disability Evaluation; D004734:Energy Metabolism / Q000502:physiology*; D005080:Exercise Test / Q000379:methods*; D005260:Female; D005684:Gait / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology; D006706:Homeostasis / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption / Q000502:physiology; D012016:Reference Values; D013223:Statistics as Topic; D016138:Walking / Q000502:physiology*