Occupational Health & Safety Management
HRM 3400 – Winter 2012 – Anna Blake
Lecture 4 – Ergonomics – Jan 30
What is Ergonomics?
- Derived from Greek word ergos meaning ‘work’ and nomos meaning ‘natural
laws of’ or ‘study of’.
- The science of work.
- The study of the mental and physical capabilities of persons in relation to the
demands make upon them by various kinds of work.
- The study of how individuals interact with their work.
- The practice of ergonomics removes the barriers to quality, productivity and safe
performance by fitting products, tasks, and environment to people.
Purpose and Goals of Ergonomics
- Occupational injury and illness reduction.
- Workers’ compensation costs containment.
- Productivity improvements.
- Work quality improvements.
- Absenteeism reduction.
- Government regulation compliance.
Methods by Which These Goals Are Accomplished
- Evaluate and control of work site risk factors.
- Identification and quantification of existing work site risk conditions.
- Recommendation of controls to reduce identified risk conditions.
- Education of management and workers to risk conditions.
The Musculoskeletal System
- Refers to the bones, joints, muscles and connective a tissue that provides the
‘body framework’ that allows the human body to move.
- Are referred to by various names
o Wear and tear injuries.
o Occupational overuse injuries.
o Repetitive strain injuries (RSI)
o Cumulative trauma disorders (CTS)
- Terms used for injuries that occur over a period because of repeated trauma or
exposure to a specific body part, such as back, hand, wrist, forearm.
- Muscles and joints are stressed, tendons are inflamed, nerves pinched or the
flow of blood restricted.
Types of Musculoskeletal Injuries
- Carpal tunnel syndrome. - Tenosynovitis
- Epicondylitis (tennis elbow)
- Low back pain – herniated disc
- DeQuervian’s syndrome
Primary Risk Factors
- Those factors that have the potential to cause repetitive strain injuries due to
- Amount of physical stressors is determined by three factors:
Refers to the position a worker assumes to do a task.
Ideal position is a neutral posture.
• Straight spine and arms hanging loosely at sides.
• Relaxed shoulders.
• Elbows close to body.
• Straight wrist.
Two types of postures are used to do work
• Those that deviate from the neutral position and can lead to
• The more a joint deviates from the natural position the
greater the risk of injury.
• Work methods
o Bending and twisting to pick up a box.
o Bending the wrist to assemble a part.
• Workplace dimensions
o Extended reach to obtain a part from a bin at a high
o Kneeling in the storage bay of an airplane (confined
Specific postures associated with injury
o Flexion/extension (bending up and down)
o Ulnar/radial deviation
o Abduction/flexion (upper arm positioned out to side or
above shoulder level)
o Hands at or above shoulder height.
• Neck (cervical spine)
o Flexion/extension o Side bending (telephone to receiver)
• Low back
o Bending at the wrist
o Muscular force
Refers to the amount of muscular effort that is required to perform a
Modified by other work risks:
• The type of posture
• Type of work (dynamic or static)
• Repetition/duration of work
Contributing workplace conditions
• Weight of hand tools
• Type of grip that must be used and relationship to worker’s
• Contact trauma
• Wearing of PPE (e.g. gloves)
o Repetitive movements
Work that is performed over and over again without providing an
opportunity for the muscles to rest.
The greater the number of repetitions the greater the risk.
The time quantification of a similar exertion performed during a
• E.g. assembly worker may produce 20 unites/hour.
Warehouse worker may lift 3 boxes/min.
The degree of injury risk is modified by other risk factors such as
force, posture, duration and recovery time.
• The time quantification of exposure to a risk factor.
• Minutes or hours per day the employee is exposed to a risk.
• Time quantification of rest between repetitions.
Workplace Components (Secondary Risk Factors)
- Work organization
o Lack of work variation where workers are performing limited number of
tasks which are repetitive.
- Work environment
o Vibration and cold temperatures can reduce blood flow to muscles causing
them to tire more easily.
o Poor lighting and glare can force workers to adopt awkward positions.
- Tools and equipment o Causes soft tissue pressure reducing blood flow to muscles.
E.g. finger regularly presses trigger.
o PPE e.g. gloves require excessive muscular force to grasp i