Analysis of possible lower lumbar strains caused by the structural properties of automobile seats: a review of some recent technical literature.

BACKGROUND: Epidemiologic studies on low back pain (LBP) persistently point to a strong correlation with whole-body vibration from motor vehicle driving. Vehicle vibration enters the driver's body through the seat. Therefore, the analysis of the vibrational properties of automobile seats is a necessary prerequisite to understanding the correlation between LBP and driving. OBJECTIVE: To examine structural properties of automobile seats that might be a source of LBP for the passenger, to modify the seat design accordingly, and to have it tested by drivers who have LBP. DATA SOURCES: Recent studies of the vibrational properties of automobile seats published in automotive technical journals not readily accessible to a medical audience are summarized and further analyzed from a biomechanical point of view. CONCLUSION: Because of the strong coupling between the seat backrest and the vehicle floor, a differential motion between backrest and seat cushion occurs when one is driving. It inevitably induces continuous strains in the lower lumbar spine of the seat occupant and is therefore a possible source of LBP. Vibrational measurements performed on a prototype automobile seat with a vertically moving backrest show that, compared with a standard seat with fixed backrest, the differential motion is strongly reduced. The resulting relief of LBP is confirmed by drivers who used this type of seat.