A force plate analysis of sitting postures on a Risshin chair (Zazen-like, upright-support seating furniture) during lectures : An exploratory and preliminary study

Background. "Posture" refers to both physical stance and mental attitude in both the East and West. Psychological research has demonstrated that posture reflects and alters emotions. In Japan, a tradition of regulating the body and mind by aligning posture exists, as exemplified by Zen meditation, and an upright sitting posture has been emphasized in school and home education. We developed the risshin chair, a modified version of the traditional school chair that helps students maintain an upright posture, and examined its educational effectiveness. Purpose. However, postural assessment in posture education involves various body parts, and holistic validation has been challenging. We propose the use of a force plate as a more quantitative and comprehensive method for measuring learners' macro-and microscopic body movements. This study aimed to obtain basic data on how the center of pressure (COP) changes between a risshin chair and a regular school chair in a quasi-educational setting in a laboratory and to preliminarily verify the effectiveness of force plate in postural education research. Method. Eleven students participated in the experiment, of whom 10 were included in the analysis. Each participant sat in a risshin chair or regular school chair and watched the lecture video in a counterbalanced order. Their COP changes were recorded during these trials, and they answered six questions on their reactions to the lecture. Results. Although we found no significant differences between chair conditions in subjective reports and in total COP length and others, the mean COP path length (p=.033, d=0.80) and mean COP area length (p=.021, d=0.88) were shorter, and the COP displacement (in the anterior-posterior direction) was also smaller (p=.006, d=1.14) in the risshin chair than in the regular school chair. Conclusions. The results suggested that the risshin chair suppresses minute, rapid swaying and results in more leisurely body movements. This study provides initial insight into the effectiveness of force plates in quantifying sitting postures with little visible movement.

This research was financially supported by the Kansai University Subsidy for Supporting Young Scholars in 2017–2018, titled "Basic research on back posture education to support attention control and social functioning of college students with neurodevelopmental disorder tendency," and was supported in part by the Japan Society for the Promotion of Science KAKENHI Grant Number 18K03082 in 2018–2023.