Objective: An anthropometric study was performed to understand the quantitative characteristics of the seating posture of Japanese pregnant drivers.
Methods: Twenty pregnant women with a mean gestation of 31.4 +/- 1.9 weeks and 20 age-matched, non-pregnant women provided written informed consent to participate in this study. A mid-sized, sedan-type passenger vehicle was used for measurement. The subjects, wearing light clothing, sat in the driver's seat of the vehicle and fastened the seatbelt after adjusting the seat to their usual driving posture. Longitudinal displacement of the slide adjuster and the reclining angle of the seat back were measured, relative to the reference position. Seating posture was investigated by measuring the coordinates of the anthropometric datum points of the drivers (head, shoulder, hip joint, knee joint, and the clearance between the steering wheel and the upper torso).
Results: The mean horizontal clearance between the lower rim of the steering wheel and the abdomen of the pregnant women was 146 +/- 56 mm, significantly smaller than that of the non-pregnant women (251 +/- 51 mm), due to the protrusion of the abdomen. There was no significant difference in seat adjustment position between the two groups. The height of the pregnant women and the horizontal distance from the lower rim of the steering wheel to the abdomen showed a moderate linear correlation in the pregnant group (R2 = 0.56).
Conclusions: Compared to previous studies, the differences of longitudinal distance were found between American and Japanese subjects without significant differences of body heights, due to the difference of body weights and abdominal circumferences. This is the first report to analyze the seating position and anthropometric parameters of pregnant drivers in an Asian population.