Ergonomic Seating Solutions: Recent Research and Case Studies
Transcript of Ergonomic Seating Solutions: Recent Research and Case Studies
Ergonomic Seating Solutions: Recent Research and Case Studies
Sharon Joines, PhDDirector of Research
The Ergonomics Center
Karl Marion, MS, CIE, CPESafety & Loss Control Supervisor - Ergonomics
West Virginia Workers' Compensation Commission
Copyright 2003 The Ergonomics Center of North Carolina All Rights reserved.
OverviewOverview
1. Ergonomic seating terminology 2. Guidelines for seating based on a recent review
guidelines, standards, and research3. Considerations when looking for ergonomic
solutions and selecting a chair4. Recent research on pressure distribution5. Case study
Copyright 2003 The Ergonomics Center of North Carolina All Rights reserved.
Review of GuidelinesReview of Guidelines
Recommendations for seating individuals in an office chair based on a recent review of
- guidelines, - standards, and
- research
Acknowledgements to:Elizabeth Covalla,Hollis Dickens, andJeff Hoyle
Partially funded by:Knape & Vogt
Copyright 2003 The Ergonomics Center of North Carolina All Rights reserved.
TerminologyTerminology
4
2
3
15
1: Backrest length2: Backrest width3: Distance between arm supports4: Seat pan width5: Arm support width
Copyright 2003 The Ergonomics Center of North Carolina All Rights reserved.
TerminologyTerminology
11
910
78
66: Seat pan depth7: Arm support length8: Distance between arm support
and seat pan edges9: Backrest angle10: Arm support height11: Seat pan height
Copyright 2003 The Ergonomics Center of North Carolina All Rights reserved.
Terminology: AnthropometryTerminology: Anthropometry
4
5 PoplitealHeight11: Seat
pan height
Seated Hip Width4: Seat pan
width
Seated Elbow Height10: Arm support height
Copyright 2003 The Ergonomics Center of North Carolina All Rights reserved.
Seat pan inclination & discomfortSeat pan inclination & discomfort
Finding: Increasing the angle between the trunk and thighs decreases the stress and load placed on the spine.
Implication: Seat pan inclination– Adjustability allows for increased angles between the trunk
and spine. – In combination with the adjustability of backrest
inclination, a positively inclined seat pan moves the spine toward the natural curvature of the spine.
– Chairs with adjustable seat pan inclinations are preferred and cause less discomfort than conventional non-adjustable office chairs.
Copyright 2003 The Ergonomics Center of North Carolina All Rights reserved.
Backrest inclination & discomfortBackrest inclination & discomfort
Finding: Increasing the angle between the trunk and thighs decreases the stress and load placed on the spine.
Implication: Backrest inclination– Adjustability should allow for increased angles between
the trunk and spine. – Should be pressure adjustable in order to provide
adequate support for different body masses. – Chairs with adjustable backrests are preferred and
cause less discomfort than conventional non-adjustable office chairs.
Copyright 2003 The Ergonomics Center of North Carolina All Rights reserved.
Lumbar support & discomfortLumbar support & discomfort
Finding: Pain and discomfort are a direct result of inadequate lumbar support, especially in the low back region. Lumbar support needs depend on height, weight, health, and gender.
Implication: Lumbar supports– Traditional fixed height lumbar supports are unlikely to
provide comfortable and appropriate support for the broad range of users.
– Backrest (lumbar support) should accommodate both body weight and size.
– Ideal lumbar support adjustability includes lumbar height, depth, and applied pressure capabilities.
Copyright 2003 The Ergonomics Center of North Carolina All Rights reserved.
Lumbar support & discomfortLumbar support & discomfort
Implication (cont.): Lumbar supports– Pressure applied to the lumbar region should be
adjustable• Adjustable seat pan – The capability of a seat pan
to slide forward (away from the backrest) and backward (toward the backrest)
• Adjustable backrest depth - The capability of a backrest to slide forward (toward the front of the seat) and backward (away from the front of the seat)
• Inflatable lumbar support within the backrest
Copyright 2003 The Ergonomics Center of North Carolina All Rights reserved.
Arm supports & discomfortArm supports & discomfort
Finding: Arm support during computer input tasks– reduces upper extremity muscle activity, – decreases perceived exertion, and – improves comfort.
Implication: Adjustable arm supports– meet the needs/preferences of the range of users
and – are more effective in reducing worker discomfort
than fixed arm supports.
Copyright 2003 The Ergonomics Center of North Carolina All Rights reserved.
Task variabilityTask variability
The postures, ranges of motion, and work intensity are different for various tasks.
Consider:– An employee performing 1 or 2 tasks – An employee performing 5+ tasks – Effect on range of adjustability?
Copyright 2003 The Ergonomics Center of North Carolina All Rights reserved.
Comparison of Guidelines
Chair Features
BSR
/HFE
S
CSA
BIF
MA
OSH
A
ISO
Res
earc
h
Recommendations Given Current Standards and
Research Goal of Recommendation
Seat Height Adjustable, about the range 14.82 to 21.84 in. (38.0 to 56.0 cm)
To accommodate the range of users to ensure that the thigh-to-torso angle is not less than 90° and the knee joint angle is greater than 90°
Seat Depth Adjustable, about the range 14.82 to 17.94 in. (38.0 to 46.0 cm)
To accommodate upper leg length for the range of users so that the legs can be positioned without compression at the back of the knee and enable the buttocks to be positioned to enable full use of the backrest
Seat Width At least 17.94 in. (46.0 cm) To accommodate hip breadth for the range of users
Seat Pan Angle
Adjustable, about the range 0° to 4° negatively inclined (CSA) and 0° to 25° positively inclined
Minimizes load placed on the trunk resulting in less discomfort and the spine moves toward lumbar lordosis
Copyright 2003 The Ergonomics Center of North Carolina All Rights reserved.
Guideline Comparisons - continued
Chair Features
BSR
/HFE
S C
SA
BIF
MA
O
SHA
IS
O
Res
earc
h
Recommendations Given Current Standards and
Research Goal of Recommendation
Seat Cushion
Cushioned and has waterfall front Front edge of seat pan should be rounded
To minimize leg discomfort due to direct seat contact
Movements of the Seat Pan
and Back Support
Independent: see backrest and seat pan angle. Backrest and seat pan should be adjusted to allow for 93° to 120° angle between torso and thighs
Reduces trunk flexion and back load resulting in increased comfort
Lumbar Support Shape
Adequate lumbar support, fit user’s lumbar curve. Provides support to lumbar area
To provide adequate lumbar support for the range of users
Lumbar Support Height
Adjustable, about the range 3.9 to 11.7 in. (10.0 to 30.0 cm)
To provide adequate lumbar support and minimize low back discomfort for the range of users
Copyright 2003 The Ergonomics Center of North Carolina All Rights reserved.
Guideline Comparisons - continued
Chair Features
BSR
/HFE
S C
SA
BIF
MA
O
SHA
IS
O
Res
earc
h
Recommendations Given Current Standards and
Research Goal of Recommendation
Lumbar Support Depth
Adjustable, optimal ranges not available: needs further research to determine ranges
To accommodate lumbar region for the range of users
Backrest Height
Standard back: 17.55 to 21.45 in. (45.0 to 55.0 cm) from upper surface of seat cushion High back: At least 2.93 in. (7.5 cm) higher than standard back
To provide adequate back support for the range of users
Backrest Width At least 14.04 in. (36.0 cm) To accommodate the back
width for the range of users
Copyright 2003 The Ergonomics Center of North Carolina All Rights reserved.
Guideline Comparisons - continued
Chair Features
BSR
/HFE
S
CSA
BIF
MA
OSH
A
ISO
Res
earc
h
Recommendations Given Current Standards and
Research Goal of Recommendation
Backrest Angle Adjustable, about the range of
93° to 120°
Minimizes back discomfort and more pressure is transferred to backrest, less on spine
Backrest Lock Lockable at various positions within the backrest adjustment range
Limits the range of motion for user preferences
Chair Tilt Lock Chair lockable at various positions within the tilt range
Limits the range of motion for user preferences
Arm Supports
Supports forearms and does not interfere with movement or tasks, avoid lifting shoulders or leaning to side
Minimizes strain on shoulders and low back during seated office tasks
Copyright 2003 The Ergonomics Center of North Carolina All Rights reserved.
Guideline Comparisons - continued
Chair Features
BSR
/HFE
S
CSA
BIF
MA
OSH
A
ISO
Res
earc
h
Recommendations Given Current Standards and
Research Goal of Recommendation
Arm Support Height
Adjustable, about the range 7.02 to 10.92 in. (18.0 to 28.0 cm)
To accommodate seated elbow height for the range of users performing a variety of tasks
Arm Support Width At least 1.76 in. (4.5 cm) To accommodate forearm
width for the range of users
Arm Support Length
At least 7.02 in. (18.0 cm). Maintain backrest contact
To allow the range of users to sit close to workstation while maintaining contact with backrest
Arm support Setback At least 5.85 in. (15.0 cm) Allows users to sit close to
workstations
Inside Distance between Armrests
Adjustable, about the range 16.77 to 20.67 in. (43.0 to 53.0 cm)
Should accommodate for the maximum elbow to elbow breadth of the design population
Copyright 2003 The Ergonomics Center of North Carolina All Rights reserved.
ConsiderationsConsiderations
1. The individual(s)2. The task (s)
– Other equipment involved in performing tasks
3. The work environment4. Stylistic vs ergonomic
– Seat pan evaluation
5. Training– How the chair supports with their work– Chair features– Ideal posture– Evaluation
Copyright 2003 The Ergonomics Center of North Carolina All Rights reserved.
Seat pan evaluationSeat pan evaluation
• Participants performed four office tasks for each chair:– upright relaxed
sitting– typing– writing, and – reading tasks
Copyright 2003 The Ergonomics Center of North Carolina All Rights reserved.
Seat Pan Evaluation Seat Pan Evaluation -- DataData
Seat Type Average Peak Pressure (PSI)
Average Contact Area (in2)
Average Discomfort Rating (0 to 10 scale)
Mfg 1a (BB-J757x - Slab) 4.49 (1.55) A 233.24 (22.84) A 1.80 (1.28) A
Mfg 1b (BB-J757 N1 - Slab) 4.61 (1.39) A 239.13 (21.43) A 2.17 (1.67) A
Mfg 2 5.50 (1.92) B 192.71 (24.49) B 3.60 (2.65) B
Mfg 3 5.90 (1.56) B 207.02 (20.90) C 3.11 (2.21) B
Seat Type Foam Type Seat Pan Width1 (cm)
Material Compression2
(cm) Mfg1a
(BB-J757x - Slab) Slab foam 51.5 4.0
Mfg1b (BB-J757 N1 - Slab) Slab foam 51.5 4.0
Mfg 2 Injection mold polyurethane 46.0 2.0
Mfg 3 Molded urethane 47.0 2.0
Copyright 2003 The Ergonomics Center of North Carolina All Rights reserved.
Pressure Distribution & Pressure Distribution & Discomfort RatingDiscomfort Rating
C207.02
B192.71
A239.13
A233.24
050
100150200250300
BB-J757
x
BB-J757
N1
Free
dom
Leap
Avg.
Are
a (c
m^2
)
Mfg 1a Mfg 1b Mfg 2 Mfg 3
B3.1
B3.6
A2.2
A1.8
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
BB-J
757 x
BB-J
757 N
1
Free
dom
Leap
Avg
. Dis
com
fort
Mfg 1a Mfg 1b Mfg 2 Mfg 3
Copyright 2003 The Ergonomics Center of North Carolina All Rights reserved.
Case StudiesCase Studies
Case 1: Small company, fast paced, more money than time• Dimension clarification ‘stature vs. popliteal height’
• Correct measurements• Dynamic workforce• Re-tooling chairs
Case 2: Similar small company, fast paced, employees performing multiple functions, image conscience, more money than awareness
• Style vs. substance
Copyright 2003 The Ergonomics Center of North Carolina All Rights reserved.
Case StudiesCase Studies
Case 3: Benefits of marketing learned from a large employer in RTP, NC• Tackling ‘presence vs. use’ chair feature issue• Cost: the image of the ergonomics effort
Case 4: Interaction of environment and chair selection mfgrwith clean room environment
• Clean room, slick floors -> poor friction• Awkward posture using stools for clean room• Task: Microscope work
Solution: • chair selection• work station reconfiguration• textured paint on the floor
Copyright 2003 The Ergonomics Center of North Carolina All Rights reserved.
SummarySummaryThe abundant supply of ergonomic chairs can be overwhelming.
Identify people’s needs while sitting – anthropometry
Identify task requirements
Identify options and features relevant to seating
Review recommendations based on: – Recent review of guidelines, standards, and research
Consider purchasing motivation– Fact based– Financially based– Stylistic or trend based