Kinematics of head-trunk movements while entering and exiting a car

The study of free and natural accessibility movements for a medium-sized car was carried out, recording the motor performances of ten participants by means of a motion analysis system. The experimental protocol used passive markers to implement a two-segment biomechanical model for the analysis of the head-trunk complex. The kinematic variables quantify the motor patterns, and showed specific features that can be related to the individual anthropometric characteristics and to the car geometry differences: tall participants used a neck flexion and a leftwards bending of the head, while short participants extended the neck and bent the head to the right. The different seat positions (short participants move forwards the seat) along with the principal need to avoid any body interference with the car, can explain the observed strategies. From the wider analysis of the movements in relation to the vehicle's features and to the anthropometric size of the participants, this approach could lead to an extension of the design criteria for those structural components of the car which have been demonstrated to significantly influence the human – machine interaction.