ergonomic chair.pdf

ERGONOMIC CHAIRERGONOMIC CHAIRERGONOMIC CHAIRERGONOMIC CHAIR

L.HARSHITH

Ergonomics

• Ergon = “work”(Greek)

• Nomoi =“laws of” (Greek)

It is . . . fitting the work, surroundings

to the worker

Factors considered:• Variation of human body sizes• Operation of the muscles and limbs• Working postures• Forces used • surroundings

Seating Comfort

1. The true objective of an ergonomic chair is to provide not

only the proper function but to ensure the more subtle

yet all important aspects of user comfort.

2. People who are more comfortable in their chairs are 2. People who are more comfortable in their chairs are

more likely to be able to sit and be productive for longer

durations.

In 1990, research found a 17.5% productivity increase in

subjects working in an ergonomically optimal setting

compared to one which was ergonomically suboptimal.

Anthropometric Data

� Sitting height

� Knee height sitting

� Buttock knee length

� Hip breadth sitting

� Sitting popliteal height� Sitting popliteal height

� Elbow rest height

� Buttock popliteal length

� Elbow- elbow breadth sitting

Ergonomic chair adjustments

�Lumbar Support

�Armrests

�Seat Depth Adjustment

�Design of Chair Controls�Design of Chair Controls

�Forward Tilt

�Seat Recline

Fixed Support

Lumbar Support

Single-Axis Adjustable Support

Dual-Axis Adjustable Support

Asymmetric

Asymmetric Adjustable Support

Recent independent university research has indicated

that over 74% of individuals tend to prefer more support

on one side of their lower back than the other.

Armrest Height

Front-to-Back Adjustability

Armrests

Width and Pivot

The arms represent approximately 10.2% of our total

body weight, which can result in considerable exertion

in the muscles of the upper back, shoulders, and neck

Seat Depth Adjustment

Good ergonomic seating incorporates several inches of

adjustable seat pan depth.

A minimum of 2 inches of adjustability is recommended while

3 inches is preferred.

Forward TiltForward Tilt

In some cases individuals may tend to sit on the front edge of

the chair.

Typically, this is associated with certain task requirements

and/or an individual’s adopted sitting habit. Often referred to

as “perching” this is a posture that may increase ergonomic

risks due to reduced support from the seat back and seat pan.

Movement is healthy. As we recline in our chairs we stimulate

blood flow and relieve the pressure on our spine. By reclining

our chair only 20° degrees (from 90° to 110°) we can reduce

the stress on our spinal discs by approximately 40%.

Seat ReclineSeat Recline

Base

Design of Chair ControlsDesirable control features include:

• Low hand and finger forces to operate

• Majority of adjustments achievable while seated

• Control motion intuitive and indicated by feel

• Control location consistent

The importance of control design and consistency increases

as chairs are shared between people. This is a common as chairs are shared between people. This is a common

requirement in multi-shift situations such as customer

support operations or call centers.

Risks and Hazards Associated With

Improper Chair Design

• Backrest:

– Working in these postures may lead to back pain and fatigue.

• Seat:

– Using a chair with a seat that is too high may force you to work with your feet unsupported or encourage you to move forward in the chair to a point where your back is unsupported making it the chair to a point where your back is unsupported making it more difficult to maintain the S-shape of the spine. These awkward postures can lead to fatigue, restricted circulation, swelling, numbness, and pain.

• Armrest:

– Armrests that are not adjustable, or those that have not been properly adjusted, may expose you to awkward postures or fail to provide adequate support.

• Base:

– Chairs with four or fewer legs may provide inadequate support and are prone to tipping.

Minimum suggested “standard” features:

• Appropriate lumbar (lower back) support with at least one

axis of adjustment

• Vertically adjustable armrests with adequate padding

• Synchronous recline with tension adjustment and back/lock

settings

• 2" seat depth adjustment

• 5" seat height adjustment• 5" seat height adjustment

Advantages

• Decreased injury risk

• Increased productivity

• Decreased mistakes/rework

• Increased efficiency

• Decreased lost work days

• Decreased turnover• Decreased turnover

• Improved morale

• Reduced incentives

Work Smarter –

Not Harder