Repeatability, reproducibility, and validity of a new method for characterizing lumbar support in automotive seating.

Human Factors: Journal of the Human Factors and... 51(2):193 (2009) PMID 19653483

This article describes a new and more repeatable, reproducible, and valid test method for characterizing lumbar support in automotive seating. Lumbar support is important because it affects occupant accommodation and perceptions of seat comfort. Assessing only the lumbar mechanism--particularly in terms of travel--is inadequate because it does not consider the effects of trim and foam. The Society of Automotive Engineers' next-generation H-Point machine and associated loading protocol were used as the basis for the new test. The method was found to satisfy minimum gage repeatability and reproducibility requirements. Validity was demonstrated through a regression model that revealed 93.9% of the variance in subjective ratings of poor uncomfortable lumbar support can be explained by two objective indicators: (1) lumbar support prominence in the full-off position and (2) effective travel. The method can be used to differentiate between seats offering two-way adjustable lumbar support. The best two-way adjustable lumbar seat systems are those that couple little to no lumbar support in the starting or off position (i.e., they are nonintrusive) with a considerable amount of effective or perceptible travel. The automotive industry has long needed a way to address the fact that consumers want more lumbar support than their seats currently supply. This contribution offers a method to objectify an important aspect of automotive seating comfort-namely, lumbar support. This should help human factors professionals produce, but not necessarily guarantee, better consumer ratings.