HL1115
Influences on Health at Work Notes

Dr. Seán Mahar

Back injury, cumulative strain, upper limb disorders, ergonomics.

The most common area of injury was the back, followed by the upper limbs or neck, then the lower limbs
(SWI95)

Ergonomics
(aka - Human factors engineering)

"the study of human characteristics for the appropriate design of the living and work environments"

- the study of human-machine interface

Ramazzini recognized the importance of ergonomics in the 1700's stating the cause of certain diseases to come from "certain violent and irregular motions and unnatural postures..." so "the natural development of the living machine is so impaired that serious diseases gradually develop"

Work physiology and biomechanics are two main facets
Anthropomorphy, a field allied to biomechanics, is the science that deals with the measure of size, mass, shape and inertial properties of the human body.

Biomechanics
The structure and function of the body are broken down into basic mechanical components such as levers and how they respond to external forces

An Italian, Giovanni Alfonso Borelli, is considered the father of biomechanics.

Biomechanical analysis of jobs:
Jobs can be broken down into component tasks

1. Basic description (push, pull or lift)
2. Body posture (stand, sit, squat or other)
3. Force exterted
4. Horizontal distance from hands to feet
5. Frequency

The body and it's ability to interface with the environment in a mechanical fashion can be described in two types of models: Static and dynamic

Work physiology
The energy demands of work and the toll they take on the body are studied

Manual Material Handling
Combined activities performed by workers, including lifting, pushing, pulling carrying and holding.
The activity most responsible for causing injury, particularly back injury is lifting. The subject of safe lifting has received more attention than any other ergonomic issue.

Syndromes associated with ergonomic issues at work go by various names in different areas:

• Work Related Upper Limb Disorders (WRULD) in the UK
• Repetitive Strain Injuries (RSI) in the UK
• Work-Related Musculoskeletal Disorders (WMSDs) in the US
• Cumulative Trauma Disorders (CTD) in the US
• Occupational Cervicobrachial Disorders (OCD) in Scandanavia/Japan

• Tendon Disorders
• Nerve entrapment disorders
• Neurovascular Disorders

Syndromes develop slowly and so are not commonly reported as being occupationally related.

A report from the European Agency for Safety and Health at Work on Work-Related Neck and Upper Limb Musculoskeletal Disorders is available on line.

Tendon Disorders

• Tenosynovitis (DeQuervain's, Trigger finger)or tendonitis
  • flexor or extensor tendons and/or surrounding synovia (joint lining membranes) become inflamed and are painful with movement.
• Ganglionic cysts
  • swollen and often painful nodules on tendons at either the wrist or adjacent to other bony articulations of the fingers
• Epicondylitis
  • An inflammation where the attachment for ligaments and tendons is made to bone

• Carpal tunnel syndrome
  • medial nerve is compressed as it passes through the carpal tunnel at the base of the palm and wrist, resulting in inflammation and loss of sensation, pain, skin dryness and atrophy of muscles in the nerve distribution area.

• Thoracic Outlet
• Vibration White Finger

The National Institute for Occupational Safety and Health (NIOSH) provides a critical review of epidemiologic evidence for work-related musculoskeletal disorders of the neck, upper extremity, and low back entitiled "Musculoskeletal Disorders (MSDs) and Workplace Factors".

HIGH RISK JOBS

• Repetitive Assembly Work
• Hand-Tool Intensive Work
• Packing, Wrapping
• Clothing Manufacture
• Meat and Poultry Preparation
• Food Preparation
• Manual Materials Handling
• Musicians
• Typing, Work Processing

Changes in the workplace

• Increase in assembly-line techniques
• Ever-increasing tempo of production
• Widespread use of power tools
• Increase in service and high-tech jobs
• Aging workforce
• Reduction in worker turnover

OCCUPATIONAL RISK FACTORS

Wrist Position

• Extreme flexion/extension
• Extreme ulnar/radial deviation
• Twisting & wringing motions

• Too large/small grip size
• Pinch rather than power grip
• High repetition rate
• Continuous static holding
• Slippery surfaces

• Shoulder/neck tension
• Elevated arms

• Impact/pressure on base of hand
• Vibration

• Cold
• Gloves

Medical Conditions

• Rheumatoid Arthritis, Diabetes, Hypertension
• Thyroid Disorders, Kidney Disorders
• Gout, Alcoholism
• Pregnancy, Use of Oral Contraceptives
• Gynecological Surgery
• Previous Trauma
• Tumor

• Hobbies: Racket and Throwing Sports, Sewing, Knitting, Gardening, Musical Instruments

POSSIBLE PRE-DISPOSING FACTORS

• Hypersusceptibility
• Onset of menopause
• Short stature
• Recent weight gain
• Small hand/wrist size
• Previous work history
• Worker morale/Job satisfaction

• Job changes
• Increased demands
• Overtime
• Schedule changes
• Loss of conditioning
• Loss of skill

Modify Job Requirements

• Allow break-in time
• Rotate tasks
• Allow recovery time
• Reduce "holding" time

• Adjust heights and reaches
• Use large muscle groups
• Vary muscle groups

• Keep wrist straight
• Optimize grip span
• Reduce grip force requirements
• Avoid ridges and projections
• Provide tool balancers
• Dampen vibrations

• Protect against cold
• Choose gloves carefully
• Isolate vibrations

NIOSH in the US offers a primer that describes the basic elements of a workplace ergonomics program. NIOSH advocates seven elements for evaluating and addressing musculoskeletal concerns in an individual workplace. The seven steps are as follows:

1. Looking for signs of a potential musculoskeletal problem in the workplace, such as frequent worker reports of aches and pains, or job tasks that require repetitive, forceful exertions.
2. Showing management commitment in addressing possible problems and encouraging worker involvement in problem-solving activities.
3. Offering training to expand management and worker ability to evaluate potential musculoskeletal problems.
4. Gathering data to identify jobs or work conditions that are most problematic, using sources such as injury and illness logs, medical records, and job analyses.
5. Identifying effective controls for tasks that pose a risk of musculoskeletal injury and evaluating these approaches once they have been instituted to see if they have reduced or eliminated the problem.
6. Establishing health care management to emphasize the importance of early detection and treatment of musculoskeletal disorders for preventing impairment and disability.
7. Minimizing risk factors for musculoskeletal disorders when planning new work processes and operations it is less costly to build good design into the workplace than to redesign or retrofit later.

   The powerpoint presentation for this lecture is available here, but be warned it is a humongous file!

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