The purpose of this study was to investigate the effects of changing seat heights (51 cm, 59 cm, 67 cm), door heights (122 cm, 138 cm, 154 cm) and seat positions (27 cm and 35 cm) in automobiles on kinematic parameters (trunk rotation, trunk angle, hip flexion angle and knee flexion angle) and kinetic parameters Qumbar moment, hip moment and knee moment) while exiting automobiles. Twelve student subjects were videotaped with 2 video cameras synchronized into a split screen system. Manipulating seat height, door height and seat position resulted in 18 different testing conditions. Real time animated graphics, as well as 3-D kinematic and kinetic parameters of the movement were obtained via a video image computer capture system and newly developed 3-D digitizing software. It was determined from the study that: a) Seat and door height had significant effects on kinematic and kinetic parameters, but not seat position, b) As seat and door height increased maximum values for kinematic and kinetic parameters decreased, c) Hip and knee flexion angles seem to be an acceptable subset of variables that can be used to evaluate ease of exit, d) It seems there exists a "critical seat height" at which an equilibrium exists between the demands of maintaining balance and stability and the need to reduce stress on the lower back when exiting an automobile, e) The behavior of hip and knee flexion angles can be predicted with a high degree of confidence via regression equations.
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