December 16, 2011

Ergonomics - Introduction

Ergonomics is the study of the interaction between people and machines and the factors that affect the interaction.

The purpose of ergonomics is to enable a work system to function better by improving the interaction between users and machines.

Ergonomics is the study of the interaction between people and machines and the factors that affect the interaction.

The purpose of ergonomics is to enable a work system to function better by improving the interaction between users and machines.



Evolution of Ergonomics

It owes its development to the same historical processes that gave rise to other disciplines such as industrial engineering and occupational medicine.

Scientific management, developed by F.W.Taylor, and motion study, developed by Gilbreth are precursors of ergonomics. Work study and scientific management were the forerunners of human engineering.

In 1857, Jastrzebowski produced a philosophical treatise on 'An Outline of Ergonomics or the Science of Work' but it seems to have remained unknown outside Poland. The name was re-invented by Murrell in 1949.

An important role for ergonomics generally and for the ergonomist working in a large organization is to act as an interface between developments in basic human and biological sciences and organizational needs. Ergonomics has generated many design guidelines and recommendations, which are made available to engineers and designers.

Some of the guidelines are as following;

12 Principles of Ergonomics

1.Work in neutral postures: Maintain the back with its natural “S-curve” intact during work
2.Reduce excessive force: Use minimum mass; use mechanical assists
3.Keep everything in easy reach: Design workplace according to human body dimensions, avoid over stretching of back and shoulder.
4.Work at proper heights: Elbow height (sitting); waist height (standing); avoid repeated bending of back during work.
5.Reduce excessive motions: Let the tool do the work; design for motion efficiency
6.Minimize fatigue and static load: Workload imposed during work is combination of postural load and metabolic load; Rotate with less demanding tasks, Provide frequent, short rest breaks
7.Minimize pressure points: Avoid concentrated pressure on skin areas; provide padding; provide anti-fatigue mats (half inch thick mat with 3-4 % compressibility)
8.Provide clearance: Design for 95th percentile and provide adjustability
9.Move, exercise, and stretch: Take “Energy Breaks”; allow for alternate postures; alternate between sitting and standing; change chair positioning; periodical monitoring of fitness. Introduce stretching exercises before shift
10.Maintain a comfortable environment: Provide appropriate lighting, task lighting, avoid temperature extremes, isolate vibration, reduce sources of noise.
11.Make displays and controls understandable: Design for expectations.
12.Improve work organization: Design task – Plan, Be involved, Communicate, Enlarge jobs, Be part of the team, Be considerate. Be a good manager.

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Rules of Ergonomics

1.Belly button rule: Loads that are held, lifted and carried should be kept closer to the belly button to avoid extended arm posture
2.Straight wrist rule: Avoid bending of the wrist, in jobs requiring frequent pushing or pulling, use thumbs instead of other fingers
3.Eye rule: Displays within visual field, avoid excessive neck tilt
4.Skin rule: Work area free from obstruction; avoid concentrated pressure on small skin areas
5.Straight back rule: Avoid bending of the body, keep your back straight, bend your legs, not your back.

Workers or operators should sit when:

1. They must work at the same task for an extended time period (30 min or more).

2. Task demands steadiness for the operator as well as the devices being used.

3. They need to be restrained to prevent their displacement by dynamic environmental forces.

Operators should not have to sit or stand for long periods with their head, torso, or limb positions skewed; they should be able to keep their heads, necks, torsos, and limbs in a symmetrical relationship as much as possible.

Operators should not be forced to work frequently or for long periods with their hands and arms above normal elbow level.

Avoid positioning operators in supine or prone positions.

Repetitive arm and leg motions should be in the direction that limbs articulate normally about typical shoulder, elbow, wrist, hip, knee, or ankle pivot points.

When both hands or both feet are involved simultaneously, create a configuration in which the motions are opposite rather than in the same direction; i.e., the right hand should rotate in the opposite direction to the left, and the right foot should push forward while the left relaxes in the aft direction.

Provide backrests for seated operators.

Provide arm rests.

Provide hand rests, when operators are using a continuously operated controller, such as desk-mounted joy stick or roller-ball control.

For computer data entry, the center of the key board should be at about elbow level. The associated visual display should positioned so that the operator’s line of sight is perpendicular to the face of the CRT.

Computer work station design guidelines are given in the “American National Standard for Human Factors Engineering of Visual Display Terminal Work Stations,” ANSI/HFS 100-1988, February 1988.

When the package (e.g., a suitcase) has smooth sides, it can be carried against the person’s hip or leg without too much stress. The weight should not exceed more than about 20 kg for males and 14 to 18 kg for females. For backpacks also similar weights are recommended.

Video - Introduction to Ergonomics by Prof Debkumar Chakraborty, IIT Guwahati


Uploaded by NPTELHRD

For further reference on design guidelines

Human Factors Design Handbook, Second Edition, McGraw Hill, 1992.

Originally posted at ergonomics-introduction
Knol Number 5

Updated 10 March 2013

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