Relationship between seat surface shape and pressure distribution in school seat models

Reaching in sitting: The effect of seat design and body manipulations

BACKGROUND

Sitting is a common and familiar position used daily as a platform for many motor activities in the workplace, at school, or at home.

OBJECTIVE

To investigate how difference in the chair design and selected sitting manipulations contribute to reach distance in sitting.

METHODS

Ten healthy subjects were required to reach forward as far as possible while sitting in an adjustable chair with 0°, 10° forward or 10° backward inclination of the seat, with and without footrest and leg support, with legs crossed, and when holding the edge of the seat with the contralateral arm.

RESULTS

In comparison to sitting with feet on the footrest, the maximal reaching distance decreased significantly when sitting on either forward or backward inclined seat (p <  0.05) and it increased when the subjects held the edge of the seat while seated with footrest and the posterior leg support (p <  0.05). There was no major effect of crossing the legs or the use of anterior leg support on the maximal reach distance.

CONCLUSIONS

Modification of the chair design could increase or decrease reaching distance in sitting. The outcome of the study provides a background for future investigations of the effect of sitting positions on reaching distance in the workplace, at home, or at school.

Changes in external ischial tuberosity width at varying trunk-thigh angles between sexes using two measurement methods

This study examined the influence of two methods and various trunk–thigh (TT) angles on external ischial tuberosity width (EITW) for 45 men and 45 women. In the experiment, the impress and seat pressure methods were applied at TT angles of 60°, 75°, 90°, and 105°. When the impress method was used, EITW remained highly consistent across the four measured TT angles with differences of 2.8 and 2.1 mm for men and women, respectively. Conversely, in the seated pressure method, EITW increased with TT angle such that differences in EITW across a full TT angle range were 11.5 and 11.7 mm for men and women, respectively. Irrespective of method, differences in EITW between genders measured approximately 12.6–13.7 mm across all TT angles. Correlation analyses revealed that hip circumference was positively related to EITW in all cases, whereas the relationship of hip width and depth with EITW varied by method and gender. Because of inherent differences in EITW between genders, these findings suggest that gender variability should be considered in seat cushion design.