Effect of seat orientation on ingress/egress joint kinematics and reach envelope.

摘要

Crew modules use recumbent seats to sustain increased acceleration in the upright direction. Entry (ingress) and exit (egress) of such seats require different techniques. Most of the existing research on ingress and egress biomechanics was done using vertically mounted automobile seats. In this study, ingress and egress and planar reach motions performed using seats mounted in vertical and horizontal orientations were evaluated. An eight camera (MX-13 series) optical motion analysis system (Vicon, Nexus, UK) was used to record the 3D kinematic data. Ten healthy male participants performed ingress and egress motions using the following three seat orientations, while reach tasks were only performed in the first two: (1) vertically mounted with a 90° seat angle, (2) horizontally mounted with a 90° seat angle, and (3) horizontally mounted with a 120° seat angle. A custom full-body marker set was used for the kinematic data collection. Visual3D software (C-Motion, Inc., Germantown, MD, USA) was used to formulate a dynamic model using this marker set to compute the joint angles for the ingress/egress tasks, while the distance from the clavicle to the finger markers during the reach tasks was used to determine reach in different anatomical planes. In general, peak joint angles and ranges of motion of the upper body were much higher in the horizontal seat than the horizontal seats. Differences in the lower body were less drastic, and change in kinematics between horizontal seats was negligible. These results suggest that ingress and egress of horizontal seats require more energy and can result in more strain on the user. Therefore, when horizontal seats must be used, ingress/egress space requirements, control placement, and appropriate user training are crucial considerations.