title: The reliability of the Extra Load Index as a measure of relative load carriage economy.
abstract: The aim of this study was to measure the reliability of the extra load index (ELI) as a method for assessing relative load carriage economy. Seventeen volunteers (12 males, 5 females) performed walking trials at 3 km·h-1, 6 km·h-1and a self-selected speed. Trial conditions were repeated 7 days later to assess test-retest reliability. Trials involved four 4-minute periods of walking, each separated by 5 min of rest. The initial stage was performed unloaded followed in a randomised order by a second unloaded period and walking with backpacks of 7 and 20 kg. Results show ELI values did not differ significantly between trials for any of the speeds (p = 0.46) with either of the additional loads (p = 0.297). The systematic bias, limits of agreement and coefficients of variation were small in all trial conditions. We conclude the ELI appears to be a reliable measure of relative load carriage economy. Practitioner Summary: This paper demonstrates that the ELI is a reliable measure of load carriage economy at a range of walking speeds with both a light and heavy load. The ELI, therefore, represents a useful tool for comparing the relative economy associated with different load carriage systems.
authors.affiliation: a School of Social and Health Sciences, Leeds Trinity University , Leeds , UK.
authors.forename: Sean
authors.initials: S
authors.lastname: Hudson
authors.affiliation: a School of Social and Health Sciences, Leeds Trinity University , Leeds , UK.
authors.forename: Carlton
authors.initials: C
authors.lastname: Cooke
authors.affiliation: a School of Social and Health Sciences, Leeds Trinity University , Leeds , UK.
authors.forename: Ray
authors.initials: R
authors.lastname: Lloyd
mesh_terms: D000328:Adult; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D015203:Reproducibility of Results; D000070857:Walk Test / Q000706:statistics & numerical data*; D000072797:Walking Speed; D016474:Weight-Bearing; D016526:Workload / Q000706:statistics & numerical data*
keywords: Load carriage; economy; ergonomics tools and methods; physiology; reliability