A study of upper-body postural parameters for measures of human-seat interaction

This study investigates how five selected upper-body parameters, including Neck Angle (NA), Head Angle (HA), Shoulder Alignment Angle (SAA), Thoracic Kyphosis Angle (TKA), and Sitting Acromial Height (SAH), are related to the measures of human-seat interaction in headrest region, which involve the perceived comfort, contact loading, and muscle activity. Experiments with 25 participants were carried out on a conventional aircraft seat at different conditions to identify and understand the significant upper body parameters that affect the human-seat interaction through cross-correlation analyses. The results show the occupant's initial HA, SAH, and SAA are correlated with multiple human-seat interaction measures for general seating. Among the body parameters investigated, HA appears to be the most influential factor in the seating experience in the upper body region under various sitting conditions. The head movement ($\Delta HA$) with different backrest inclinations is found to be closely associated with the headrest contact loading. This study highlights the dependence of the sitting experience on the characteristics of an individual's natural upper-body position and movement when seated, considering both subjective and objective measures. The findings from this study can be used as anthropometric reference guidelines in seat design and optimization to satisfy more customized demands from the perspective of the individual's body characteristics.