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Researches in ergonomics concerned with designing the seats to match the physiological, psychological and anthropometric requirement of the users. The objective behind these is to provide the furniture that ensures the maximum relaxation of the muscles otherwise if the furniture does not meet the physiological, psychological and anthropometric requirements of the users, it will effect:
- On the total output i.e. it will decrease
- For the body
- Results in pain in the effected parts
- Last of all, postural disorders and spinal complaints.
Procedure: When designing an ergonomical seat, comfort is taken as the criterior, on the basic that ergonomically unsatisfactory seats are uncomfortable. Excessive muscular strain brings on fatigue, whereas greater degree of comfort in a restful posture with relaxed muscles. Keeps the spine in a natural shape and brings the maximum output. It also protects the body from irreparable damage. So the seats which are meant for rest and recuperation must provide a high level of comfort with corresponding muscular relaxation.
In order to provide the maximum degree of comforts to the users the following methods should be adopted:
- Collect the following anthropometric data of user’s population
- Height: The vertical distance form the feet to the highest point of skull.
- Sitting Height: The vertical distance from the sitting surface to the top of the skull.
- Shoulder Height: This is the vertical distance form the sitting surface to the uppermost point of the shoulder with subject sitting erect.
- Arm Reach: The horizontal and vertical distance from the shoulder to the tip of the middle finger.
- Elbow Height: This is the vertical distance from the sitting surface to the elbow. In this the subject sits erect with her upper right arm.
- Elbow to Elbow Width: This is the horizontal distanced between the outer edges of elbows. This is measured by making the person sit normally with arms bent at elbow joint with right angle between the forearm and the upper arms.
- Hip Breadth: This is the maximum horizontal distance across the hips. The subject sits erect with the knees and ankles at right angle when taking this distance.
- Popliteal – Height or Length: It is measured from the ground to the position below the knee (poplited region)
- Sitting Height: Distance from the seat to the highest point of the skull.
- Shoulder Height: This is vertical distance from the seat to the shoulders. It is taken in the normal sitting posture.
- Elbow Rest Height: This is measured from the seat to the lower edge at elbow joint in normal sitting position with fore – arms at right angle to the upper arm.
- Buttock Knee Length: The horizontal distance from the rear most point of buttocks to the foremost point at knees.
- Buttock Popliteal Length: This is horizontal distance from the rear point of buttocks to the popliteal region.
- Thigh Clearance Height: The vertical distance from the lower and upper part of the thigh.
- Seat Width: The horizontal distance between hips is measured which is known as seat width.
- Squatting Width: is measured by making the subject to sit in squatting position with insteps of feet 9" apart. The distance form the rear most point of buttocks to the outermost point at knees is measured which is known as squatting width.
- Squatting Height: The vertical distance from the ground to the highest point of skull in squatting posture is the squatting height.
- Knee Height: is measured from the ground to the portion below the knees popliteal region.
- Lower Leg Height: This is the vertical distance from the floor to under of thigh immediately behind the knee.
After collecting the data on the above mentioned point find the percentile value of each at 5th percentile, 50th percentile and 95th percentile.
On the basis of this we can decide the dimension of any part of furniture.
After the anthropometric data, make the identification of critical discussion of each item. Such as in case of chair, the critical dimensions will be seat width, seat height, seat depth, arm rest and back rest.
For deciding the height of the seat, we have to take the lowest percentile value, because it can be suitable for the others having higher height, but for other dimensions always maximum percentile value is taken.
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