Examination of School Furniture by Measurement of EMG and Body Pressure Profile and Consciousness Investigation of Learner Change in university student's consciousness and tired feeling according to change in height of desks and chairs

摘要

The motions analysis and the muscle activity were measured for eight university students who were using furniture for the school. The desks and the chairs used were the numbers of sizes from the second to sixth sizes of Japanese Industrial Standard, and they were wooden desks and chairs, the height were able to be adjusted. The measurement was based on the height of the desk and the chair of the proper sizes calculated from the height of the students. The height of the desk and the chair was changed into 3 steps, that is the proper size, the minus one level size and the plus one level size of JIS. The change of the load value and the movement of the center of gravity of load distribution were analyzed with a body pressure profile measuring system. The muscle activity was measured by putting on the electrode to the erector spinae muscle and the trapezius muscle, and using the surface EMG (electromyography). After that, the muscle fatigue was examined by the analysis of RMS (root mean square) method. While measuring it, the student did the work of copying sentences sitting on a chair, and they answered the questionnaire survey concerning height of the desk and the chair and their tiredness. The result of this experiment was as follows. When one level high desk and the chair from the proper size were used, the fatigue degree comparatively became small in the erector spinae muscle, but a remarkable difference was not seen in the trapezius muscle. When the desk and the chair of proper size were used, the movement of the center of gravity of load distribution was suppressed. It has been understood that body pressure of the ischiadic nodal point of hips moves to the other side of the femoral region and the pressure is dispersed when one level high desk and the chair are used. And according to the consciousness investigation by the questionnaire, there were a lot of answers that it was the most appropriate height when the desk and the chair were used at a proper size of JIS. Moreover, tiredness was felt most when one level low desk and the chair were used, and there were a lot of answers that especially felt tiredness in a waist and a right shoulder.