Anthropometry application on factories

Anthropometry

• It is the concerned with size and proportions of the human body. It is derived from the greek words ( anthropos = man), metron = measure . There are three type of anthropometric data.

1- structure type which is concerned with body

dimension of the subject in static positions from anatomical landmark to fixed point in space

• Data for body dimensions always refer to a particular group and not necessary apply to other population group for example a table height , which is suitable for a person can be unsuitable for another one.

• When a table height is adjustable over a sufficient range , several people can use it . Most anthropometric data are expressed in terms of percentiles

• Percentiles : indicate the percentage of persons within the population who have a body dimension of certain size or smaller .

• For example: if the 95th percentile in stature or

height is 167cm that means the 95th percent of the study population would have same height or lesser heights and 5 percent of the study population would have greater heights

2- Functional type : related to the surrounding zones of body reach.

3- Newtonian type : for mechanical analysis of load on body (lift)

In standing

• The following structural anthropometry can be measured : stature or height of the subject during standing , standing eye height, standing shoulder height , standing elbow height, chest depth , abdominal depth…….

• The functional anthropometry : includes reach zones during standing , forward grip reach , vertical grip reach, side grip reach……..

In sitting • The following structural anthropometry can be

measured . Sitting height, sitting eye height, sitting elbow height, shoulder sitting height, buttock pop length, buttock knee length …

• The functional anthropometry: include reach zones during sitting, forward grip reach, vertical grip reach, side grip reach . It also includes working zones and needed zones during working.

Functional anthropometry • It is necessary to avoid excessive reaches or to limit

the extent of forward and sideways reaches to avoid excessive bending or twisting of the trunk.

• the control panel and the tools which are in regular

use , shoulder be located directly in front or near the body .

• The most important operations should take place within a radius of approximately 50cm.this value applies to both seated and standing work

Anthropometry of seat design

• In order to reach the best design of the chair at which different kind of loads will be decreased, it is essential to study the guidelines of seat design and its anthropometric consideration.

• There are certain guidelines for seat design ,these include (1) the shape and dimensions of the seat in relation to the reason for sitting (2) the dimension of the seat in relation to anthropometric dimension of the sitter

(3) the support and stability provided by the chair to the sitter . (4) the flexibility of the seat to provide variable angulations. (5) the presence of resting surface like lumbar rest, arm rest, foot rest and (6) the presence of padding

Anthropometric seat considerations

• Chair have been classified into 3 types or families , easy chair, work chair ,and multipurpose chair.

• For each type , certain dimensions must be taken into consideration, seat height, seat width, depth, and angle in addition to backrest height, width and angle, and armrest height.

• The easy chair : is a chair which is preferred to relax the posture, it can be considered as relaxing chair

• The work chair : is a suitable chair for subject during performing certain job

• A multipurpose chair : is a modern type of chairs which has been used recent, it allows to move around his place and perform different tasks

• The seat height: is adjusted correctly when the thighs of the sitter are horizontal , the lower legs are vertical and feet are flat on the floor.

• If the subject is short person , his feet would not be able to rest on the floor because of mismatching between seat height and lower leg length. He is advised to use foot rest to avoid compression fatigue of the thighs or increasing curvature of the lumbar spine

• Another problem results from a tall person who will make more leaning forward on the table surface by his trunk and that increases the kyphotic posture.

• The seat height differ according to the chair type, the height of an easy chair should allow the legs to be stretched forward because it is preferred relaxing postures for the feet, in addition to helping to stabilizing the body

• The working chair : the sitter is likely to be in a more upright position with his feet flat on the floor . The height of a working chair should be adjustable to be suitable for a wide range of workers.

• Finally the optimal height for a work seat can also be decided in relation to the height of the worker surface , which should be between 24 and 30 cm below the working surface to provide clearance zone for the thigh under the working surface and to prevent undesired movement of the body in case of decreasing of the clearance zone

• The seat depth : is important because it ensures that the lumbar area is supported from the backrest . It should be correspond with the buttock – popliteal length or thigh length of the person

• In case of short person : the seat is deeper than the thigh length of the person. As a result of this mismatch , the front edge of the seat will restrain him, causing his lumbar area to be curved to reach the backrest and there is pressure at the back of the knee against the seat

• In the tall person: the thigh length is longer than the seat depth so the knees will be protruded slightly at the front causing a compression fatigue in the thighs . The seat depth from 40-43 for easy and 35-40 for work chair

• The seat width : should be made in correspondence with the dimension of the hip width , which differ according to sex and age . Average 43-45 cm.

• The seat angle : it is an angle which is made by the seat with the horizontal plane . The seat could inclined forward or backward.

• inclined backward produce two effects

(1) the back is supported to reduce the static load on the back muscles.

(2) it prevent the sitter from gradually slippage out of the seat after long period of time

• The easy chair : is inclined backward to relax the back

• the work chair : is inclined forward because the sitter wishes to reach the area in front for work

• A forward inclined chair called Balans chair which has 20 degrees forward inclination with knee support but can’t used for long time

• The backrest height 48-63cm• The backrest width 35-48 cm• The backrest angle more than 95 degrees till 110-

120 degrees with lumbar support about 5cm square in its contact area

• The resting surface (arm, foot…) is corresponding with the body dimensions