Inter-individual variability in load carriage economy and comparisons between different load conditions.

Equivocal findings exist for the economy associated with load carried close to the body's centre of mass. Individual variation could explain some of the equivocal findings. This research aimed to examine the extent of individual variation in loaded walking economy. Eighteen females carried load on the back, head and split between the front and back. Individual variation in relative load carriage economy (ELI) was primarily assessed using standard deviation, coefficients of variation (CV) and intraclass correlation coefficients (ICC). There was large inter-individual variation in ELI values with highest mean CV's of 16%, 12% and 10% for head-, back- and combined front and back-loading. Mean ELI values were not significantly different between methods. The large amount of individual variation found here suggests future load carriage research should account for individual variation, particularly when considering sample size and when making inferences on the economy associated with different types of load carriage using group mean data.