Ergonomics & Workplace Biomechanics

Question 1

What is ergonomics?

Answer 1

The study of the interactions between people and machines

Question 2

Ergonomic improvement to work systems can be achieved by doing what?

Answer 2

• Designing the user-interface (ways the person interacts with equipment) to be more compatible with task and the user
• Change work environment to make it safer and task specific
• Change task to suit user characteristics (alter job)
• Organise work to accommodate psychological and social needs of people

Question 3

Effective application of ergonomic changes to the workplace should eliminate a number of aspects
that are undesirable. List these 5 undesirable aspects.

Answer 3

• Inefficiency
• Fatigue
• Accidents, injury or error
• User difficulties
• Low moral and apathy

Question 4

Why is the science of anthropometry an important component of ergonomics?

Answer 4

• Each person also has their own comfort zone in which they are able to perform tasks with the least stress and strain on the body
• Working in poor postures in workstations not designed to accommodate physical needs → increased injury

Question 5

How might an ergonomist use anthropometry in designing or modifying a work task/environment?

Answer 5

• Tables list means and standard deviations of populations
• Different tables for different populations
• Examples:
  
  • Nationality
  • Sex
  • Ages
  • Body size

Question 6

Explain what a percentile score is and how they are used in ergonomics.

Answer 6

• Percentiles are used to describe how far an observation is away from the mean as a function of the standard deviation.
• Ergonomics designs accommodates for 90% of the population which is between the 5th and 95th percentile.

Question 7

Explain the difference between postural stress and task-induced stress.

Answer 7

Postural stress - Denotes mechanical load on the body by virtue of its posture

Task-induced stress - Depends on mechanical effort needed to perform the task

• High task stress
  
  • Digging a trench (high postural stress)
  • Competitive weightlifting (low postural stress)
• Low task stress
  
  • Painting a ceiling (high postural stress)
  • Reading a book (low postural stress)

Most biomechanical stresses are unnecessary if they are postural and can be reduced if the task was redesigned to improve the posture

Question 8

What is posture and how is it controlled?

Answer 8

Posture - position or arrangement of the body and its limbs

Postural Control
- Postural mechanisms allow the maintenance of body position in relation to the environment and also the position of the head and eyes in relation to gravity

• Postural mechanisms rely on input from visual, vestibular and proprioceptive sensory systems
• Maintenance of posture is not just a matter of simple reflex adjustments but typically involves plastic and adaptive modulation of spinal reflex circuits to suit different requirements

Question 9

Why is it incorrect to instruct a worker to maintain a “straight back”?

Answer 9

• ‘S’ shape of an erect posture gives structure a ‘spring-like’ quality
• Better to absorb sudden impact especially in walking
• Loss of ‘S’ shape in sitting may lead to back pain

Question 10

What are the 4 main risk factors for musculoskeletal disorders in the workplace?

Answer 10

• Force (higher than tolerable forces)
• Posture (where and how forces are loaded)
• Repetition (those loading of forces happen repeatedly)
• Duration of task

Question 11

Explain the “pros” and “cons” of standing in the workplace.

Answer 11

Pros

• Reach is greater in standing than sitting
• Body weight can be used to exert forces
• Standing workers require less leg room than seated workers
• The legs are very effective at damping vibration
  
  • Flexed knees and hips - absorbs vibrations
• Lumbar disc pressures are low
• It can be maintained with little muscular activity and requires no attention

Cons

Question 12

Explain the “pros” and “cons” of sitting posture in the workplace.

Answer 12

Pros
- While sitting, you can keep your spine balanced (“Neutral”) by again “stacking” ears over shoulders and shoulders over hips

Cons
- If not seated properly, this can result to lower back pain

Question 13

Why is it important to have ergonomic seating in the workplace?

Answer 13

• Sitting increases postural stability for fine motor tasks

- More stable posture decreasing extraneous movement

Question 14

List several myths of ergonomic seating

Answer 14

• Ergonomic seating always requires a single, ‘cubist’ (90° upright) postural orientation that is independent of the user’s task (Dainoff, 1994)
• You can judge how ergonomic a chair is by briefly sitting in it
• Users should be able to adjust everything
• Users don’t need training on how to sit in a chair (Dainoff, 1994)
• One chair design will provide the best fit for all users

Question 15

Name at least 5 key features of ergonomic chair design.

Answer 15

• Lumbar Support
• Adjustable Lumbar Support
• Chair Dimensions (seat adjustability)
• Arm rests
• Pedestal