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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