In-chair movement: validity, reliability and implications for measuring sitting discomfort.
Sitting discomfort is traditionally evaluated with subjective rating scales which are referenced to an objective correlate (e.g. sitting posture) measured on a static (i.e. non-continuous) basis. Since sitting discomfort is dynamic in nature, it requires continuous, objective measurement. We therefore adapted an interface pressure mat to continuously record in-chair movement (ICM) as an indirect measurement of sitting discomfort by tracking the center of pressure (COP) at the buttock-chair interface. Here we report on two phases in the development of the COP system: laboratory validity and field reliability. In the laboratory study we confirmed system validity by simultaneously tracking ICM with the mat and a force platform (r2 > 0.80) and by comparing subjects' COP movement with their gross trunk movements (r2 > 0.86). In our field study we used the intraclass correlation coefficient to establish a data sampling (i.e. selection) protocol that was reliable. We collected ICM data on seated telecommunications Directory Assistance operators during 2 h field tests. Results showed that using a minimum sampling time of 5 min and then averaging a series of 5 min samples of ICM was more reliable than single discrete samples. Using the averaging protocol, we also showed that ICM increased significantly over 2 h and that ICM did not differ between trials.
Fenety
P A
PA
School of Physiotherapy, Dalhousie University, Halifax, Nova Scotia, Canada. anne.fenety@dal.ca
Putnam
C
C
Walker
J M
JM
D000328:Adult; D001696:Biomechanical Phenomena; D006804:Ergonomics; D005260:Female; D006801:Humans; D007374:Interior Design and Furnishings; D008297:Male; D008875:Middle Aged; D009068:Movement; D011187:Posture / Q000502:physiology; D013647:Task Performance and Analysis