Furniture and Furnishing

Furniture and Furnishings 3(1+2)

Lesson 10:Functional Designing Of Furniture And Its Evaluation Techniques Based On Ergonomic principles

Evaluation Of Existing Furniture

1. Physiological Responses: The dimensions of the furniture can be evaluated on the basis of the physiological responses of users such as:
   • Heart rate
   • O2 consumption
   • Respiration frequencies
   • Blood pressure
   • Electrical activity of muscles by means of electromyography.

The minimum level of all these is taken as the ideal for furniture design.

2. Subject Responses: The evaluation of available furniture is also made on the basis of the subjective responses of the users.
   1. Make the person sit on chair which is available.
   2. Record the length of time a person is prepared to sit on that chair
   3. Record the frequency with which the person changes his posture
   4. Record the time needed to produce a sensation of discomfort in the parts like, neck, shoulder, upper back, lower back, thigh, knees, upper leg, lower leg, buttocks, feet and any other, for the given dimension of the chair for short, medium and tall subject.
   5. Record the time needed to produce the intolerable pain on the above mentioned point when the person just can not sit on that.
   6. The minimum time the person can sit shows the most uncomfortable design, whereas the maximum time the person can sit shows the most comfortable design.

   This way any two chairs, table, stool or beds can be evaluated by this method.
   Along with this the subjective responses of the users can also be recorded such as:

   1. The seat was too sliding
   2. The seat was too shallow
   3. The seat was too high
   4. The surface of the seat was hard
   5. The arm rest was not comfortable
   6. The material used for the seat was slipping and resistant to the moisture absorption.
   7. Back rest was too high or too low
   8. The seat was overall tiring

On the basis of these responses the different designs of chairs, tables, resting chair, stool and bed can be compared.

During the few experiments conducted in the practical classes in the Department of Family Resource Management, College of Home Science, the following results have been found out.

1. The effect of different height and depth of chair on the body of the users.
   For this the chair which was adjustable in height and depth was taken. The three subjects of different height i.e. tall, short and medium were selected. Each one of these is made to sit on the chair for ½ an hour or till she could sit without any one selected height and width of the chair. The responses were recorded on the above mentioned point. This was repeated for each subject and on each height and depth. Then in the end the results were complied. It showed that:
   • Height and depth played an important role in determining the comforts of the users
   • The discomfort increased gradually as the height and depth of the seat was increased for all the subjects
   • The comfortable height and depth for all the subjects was recorded as 12.5" and 17" respectively.

   The posture of each subject on each height and width was also drawn on the graph paper form the following measurements just to see the postural attitude of each subject:

   1. Position of feet - from back edge of the chair to heel edge
   2. Vertical position of knees - from seat to popliteal point in vertical direction
   3. Horizontal position of knees - from seat to popliteal point in horizontal direction
   4. End of buttocks - from back rest to end of buttocks
   5. Lower back - seat to starting point of contact with back rest
   6. Upper back - seat to last point of contact with back rest
   7. Position of Head - back rest to back of head & seat to head level vertically

   By taking all these measurements on the graph the posture of each subject on each height and depth was drawn just to see the spinal attitude. The posture where there was minimum bending was taken comfortable.

2. In the second experiment the evaluation of various available resting chairs were done in the same way.
3. In the third experiment the effect of varied height of office table and chair on the body of the users was recorded in the same way, and it was concluded that the table height of 30" with seat height of 12.5" is comfortable for the tall subjects and table height of 27.5" with seat height 17.5" for medium and short height subjects.
4. In the fourth experiment the effect of different height of the ironing board and the body of the users in ironing was recorded. Four different height of the ironing i.e. 37.5", 34.0", 30.0" and 20.0" for tall, short and medium height subjects were tested on the basis of their subjective responses. From the results it was concluded that highest and lowest height was most uncomfortable. Moreover lowest was much more uncomfortable than the highest because of the hyphosis curvature of the spine in the former for all the subject. The heights of 30” and 34" of ironing board were found most comfortable for all the three subjects, i.e. taller, medium and shorter.
5. In the next experiment the effect of varied height of revolving stool on the body of users while grinding the masala was studied. Three piheris of different heights were selected 10.5", 7.8" and 5.0" for three subjects of different heights e.g. tall, short and medium. The activity of grinding was done for ½ an hour and the discomfort on the different parts were recorded just by the subjective responses. The results of the experiment showed that the height of 5" is comfortable for the person of 67.76" and 10.5" for the 60.44" height person and 7.8" for 62.96" height of person.

Similarly the designs of other furniture can also be evaluated on the basis of subjective feeling and the designs which cost minimum to the body should be selected.