Week 03 (Workplace biomechanics and lifting)

Question 1

How is biomechanics linked with ergonomics?

Answer 1

Increasing efficiency and decreasing the risk of injury by reducing the stresses (loads) applied to the body.

Question 2

List 5 types of stress applied to the body?

Answer 2

1. Shear stress or strain
   
   • between femur and tibia
   • disc problems increasing hyperlordosis
2. Compression forces
   
   • patellar pain
   • hip joint
   • fractures to the vertebrae
3. Tension forces
   
   • ligament avulsion fractures
4. Bending forces
5. Torsion forces

Question 3

In relation to back stress, explain the difference between type A, B and C injuries.

Answer 3

Type A injury = single event
Type B injury = sequence of sub max stresses
Type C injury = continuous low grade stress (chronic overuse)

Question 4

What factors are involved in back stress?

Answer 4

• Body weight and mass distribution (increased load, shifting COM relative to base of support, effects posture)
• Level of muscular strength / support / imbalance
• Intra abdominal pressure
• Position during load: flexion / extension, rotation, lateral bending
• The resultant compressive and shear forces acting
• Many of above factors influenced by activity and lifestyle

Question 5

Who is NIOSH and what do they do?

Answer 5

Provides a quantitative starting point for comparing tasks

Once calculated recommended weight limit (RWL) - then
- calculate the lift index (LI) = actual load lifted / RWL
- Likely that Li > 3 poses a significant risk to many workers ( < 1 is protective)
- Lots of limitations though

Question 6

Reductions in workplace back injuries can be achieved by: a) risk identification; b) risk assessment & c) risk control. Explain each of these phases.

Answer 6

Risk identification
- Analysis of workplace injury records
- Consultation with employees
- Direct observation (analysis)

Risk assessment:
- Level of risk vs cost-benefit analysis of…
- Actions and movements
- Workplace and workstation layout
- Posture and position
- Duration and frequency of manual handling
- Location of loads and stances moved
- Weights and forces
- Characteristics of loads and equipment
- Work organisation (flow, order)
- Work environment
- Skills and experience
- Age
- Clothing

Risk control:
- Job redesign
- Mechanical handling equipment
- Training
- Other administrative controls
- safe manual handling checklist

Question 7

What is a lumbar motion monitor and how might it be used?

Answer 7

Tools for Risk Assessment and Task Redesign:
a) Lumbar Motion Monitor
- measures static and dynamic trunk postural variables that predict risk of back injury

Question 8

• List 3 strategies to prevent an overexertion injury.

Answer 8

• Design the task for all workers
• Select workers believed to be at low risk
• Train workers to reduce their personal risk levels

Question 9

• What does “lifting limits in manual handling” mean?

Answer 9

• Setting ‘safe’ limits for employees
• But broad and indirect
• ‘gold standard’ for workplace

Question 10

• Quantified lifting injury risk increases when?

Answer 10

• Heavy objects are lifted
• The objects is bulky
• The object is lifted from the floor
• Objects are frequently lifted
• Poor grips are provided

Question 11

Which style of lifting is best?

Answer 11

• L4/L5 disc force will decrease with hip/knee flexion but then tibio-femoral force increases, depend on person

Question 12

• List several important computer workstation features in relation to:

Answer 12

1. The operator: position of head, shoulder, arms, brightness
   
   2. Equipment placement / design: correct chair dimensions, style, table height
   3. Workstation environment:
   4. Workload and operator breaks: Moving regularly, breaks