Seated Work and Workplace Design

Question 1

Main contact points

Answer 1

Seat is the main support

Through the ischial tuberositites and the soft tissue

Question 2

Secondary contact points

Answer 2

Feet to floor/chair
Back to backrest
Arms to armrest

Question 3

Advantages of siting posture

Answer 3

Stability for tasks requiring fine motor movement or conc vision
Less energy than standing
Reduces stress on LE
Reduce hydrostatic pressure on legs

Question 4

Seated posture reflects

Answer 4

the task, chair, individual

Question 5

Seated postures - based on

Answer 5

Center of mass location relative to the ischial tuberosities

Question 6

Seated posture - Affects

Answer 6

% TBW transferred to different supported surfaces

Affects/reflects lumbar spine position

Question 7

The more ant tilt you have

Answer 7

the more lordosis you have

Question 8

The more post tilt of the pelvis

Answer 8

the lordosis will disappear and may end up with some kyphosis

Question 9

Posture selected reflects

Answer 9

Individual seating habits
Task demands
Height and inclination of chair seat
Position, shape, inclination of backrest
Presence of other types of support

Question 10

Sitting relaxed (no sacrum support)
CoM
Feet support
Lumbar spine
Disk pressure
EMG

Answer 10

CoM directly above IT
Feet support about 25% of TBW –> lumbar spine is straight or in slight kyphosis
Disk pressure higher than standing, same EMG activity

Question 11

Sitting erect (no sacrum support)
CoM 
Lumbar spine
Disk pressure
EMG

Answer 11

CoM directly above IT
Achieved by rotated pelvis ant
Lumbar spine is in slight lordosis 
Disk pressure lower than relaxed sitting
Same EMG activity

Question 12

Sitting leaning forward
CoM
How to achieve this position
Disk pressure
EMG

Answer 12

CoM in front of IT
Tilt pelvis forward or leave pelvis and induce kyphosis of the spine
Both cases - disk pressure higher than standing
EMG activity inc

Question 13

Sitting leaning back
CoM
Feet support
Disk pressure
EMG

Answer 13

CoM behind IT
Feet support less than 25% of TBW
Backward rotation of pelvis and kyphotic lumbar spine
Disk pressure same as relaxed sitting, higher than standing
EMG activity lower

Question 14

Disk force reflects

Answer 14

posture and supported load

Question 15

Reduction of force - achieved by

Answer 15

arm support, sitting straight, and unsupported feet

Question 16

Greater force found in

Answer 16

ant leaning, which was reduced by straight back

Question 17

Posterior leaning force is similar to

Answer 17

relaxed sitting force

Question 18

Office desk and disc force - disc force reflects

Answer 18

Posture, supported load, task, environment

Question 19

Office desk and disc force - lower force was found when

Answer 19

writing and when depressing a foot pedal

Question 20

Office desk and disc force - higher force was found when

Answer 20

typing and when lifting a weight

Question 21

Backrest inclination - the more you have

Answer 21

the less activity of the erector spinae

Question 22

Lumbar support vs backrest inclination - which has biggest difference

Answer 22

Use of lumbar support more important than backrest inclination

Question 23

To reduce disc pressure when seated

Answer 23

Use lumbar support

Increase backrest inclination

Question 24

Writing at desk

Answer 24

Dec noted compared with other tasks

Arms supported by the desk

Question 25

Typing and lifting a phone

Answer 25

Inc pressure Larger external load moments Stability requirements

Question 26

Leaning forward unsupported does what to disc pressure

Answer 26

inc

Question 27

Posture fixity

Answer 27

maintaining the same posture for a period of time We want to reduce this 10-15 minute breaks for every 2 hours seated

Question 28

Seat angle and erector spinae

Answer 28

No differences

Question 29

a good chair

Answer 29

functionally adapts to the occupant and the task

Question 30

Comfort frequently defined as

Answer 30

the absense of discomfort

Question 31

Determining comfort based on

Answer 31

Observe body posture and movement Observe task performance Direct subjective ratings of general comfort

Question 32

Foot support - High sitting

Answer 32

Affects circulation Pressure applied close on thighs close to the knees Leg swelling --> pressure on sciatic nerve Should not feel the edges of the chair

Question 33

Foot support - high sitting - semi seated position

Answer 33

eases transition to standing but increased lower extremity stress

Question 34

Seat height affects buttocks pressure - low seat height =

Answer 34

too small contact area

Question 35

Seat height affects buttocks pressure - high seat

Answer 35

stresses on the legs inc which may cause swelling

Question 36

Clinical aspects of seated posture

Answer 36

Avoid postural rigidity | Workers must be altered to problems occurring from long lasting low level muscular efforts

Question 37

Workstation Goal

Answer 37

Function, comfort, user friendliness, minimizing spinal disc forces

Question 38

Workstation - lumbar support

Answer 38

Use backrest that has lumbar support allowing for spinal curvature similar to standing

Question 39

Workplace - leg positions

Answer 39

movement of pelvis caused by different positioning of knees and hips

Question 40

Workplace - seat design

Answer 40

tilted seats, contoured or cushioned support to ideally position pelvis, use of armrest, adjustibility, seat width, height and depth

Question 41

Workplace - desk design

Answer 41

bottom height, top height, inclination of surface, work suface size, surface friction