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A need to develop methodologies to obtain objective measurements of the effects of different seat contours on people is evident. In an effort to monitor muscle activity during static seated postures, electromyography (EMG) was employed. In an experimental setting, fatigue was induced in back extensor muscles for different seated postures. The resultant EMG signals were then sampled bilaterally for three different vertebral levels and the effects of the different seating systems on posture were evaluated. In preliminary tests involving 4 subjects of similar size and build, utilizing three differently contoured seats, findings support the use of EMG to quantify muscular fatigue as a viable means of objectively measuring the effects of different seat contours.

The location of the pelvis in the seated automobile operator is critical for proper packaging and seat comfort design. The pelvis is the skeletal structure which contains the hip joint (H-point) and ischial tuberosity (D-point). The orientation of the pelvis largely determines the curvature in the low back which is supported by lumbar supports in the seat back. A methodology has been developed that uses onboard video and pressure measurement systems to locate the pelvis. This system has been used in a mid-sized vehicle on seated operators driving the vehicle on the highway. This paper describes the methodology and the location of the pelvis in seated automobile operators.

A vehicle laboratory has been developed in which the vehicle operator's posture, pressure distribution, muscle activity, and comfort can be measured while driving on the highway. This instrumented vehicle uses video camera, pressure mats, electromyography, and questionnaires to make these measurements. There is an on-board PC486 to record the data fro later off-line analysis. These data are useful for developing design criteria for seating comfort as well as investigating the real-life position that the operator sits in the vehicle package while driving the vehicle on the highway.