OHS Code Explanation Guide

Published Date: July 01, 2009
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Part 14 Lifting and Handling Loads

Section 211 Musculoskeletal injuries

Musculoskeletal injuries, or MSIs, go by many different names, including repetitive strain injuries, repetitive motion injuries and cumulative trauma disorders. Whatever the term used, the effect is the same: bones, joints, ligaments, tendons, muscles and other soft tissues are being injured.

MSIs also have some more familiar names. Tennis elbow is an MSI that can result from the repetitive swinging of a tennis racquet or from other repetitive arm movements similar to those used by tennis players. Other MSIs have similar names that indicate the type of work being done, for example, carpet layer’s knee, letter carrier’s shoulder and pizza cutter’s wrist. MSIs also have medical names such as carpal tunnel syndrome, thoracic outlet syndrome and tendonitis.

Section 1 of the OHS Code defines a musculoskeletal injury (MSI) as an injury to a worker of the muscles, tendons, ligaments, joints, nerves, blood vessels or related soft tissues that is caused or aggravated by work and includes overexertion injuries and overuse injuries.

Overexertion and overuse injuries can be described as follows:

  1. overexertion injuries e.g. sprains, strains and tears resulting from excessive physical effort as might happen during lifting, lowering, pushing, pulling, etc; and

  2. overuse or repetitive motion injuries e.g. resulting from repeated overuse of a part of the body. While it is commonly believed that computer users experience high levels of repetitive motion injury, the problem is rarely recognized among those workers who use their hands extensively in food processing, materials handling and the professional trades.

The reason MSIs are the subject of the OHS Code is that they are the leading cause of lost-time injury claims in Alberta. In each of the years from 1997 to 2008, according to data provided by the Workers’ Compensation Board – Alberta, the percentage of all lost-time claims due to MSIs ranged from approximately 26 percent to 30 percent. The next closest category, “struck by object”, represented approximately 13 percent of all claims. MSIs are a serious source of injury and a largely unrecognized source of productivity and financial loss for employers.

Subsection 211(a)

If a worker reports to the employer what the worker believes to be work related symptoms of an MSI, the employer must review the activities of the worker to identify work-related causes of the symptoms, if any.

An injury is probably work related if

(a) an event at the work site either caused or contributed to the resulting injury, or
(b) an event at the work site significantly aggravated a pre-existing injury.

Work-relatedness is presumed for injuries resulting from events occurring at the work site. An injury is not work related if it involves signs or symptoms that surface at work but result solely from a non-work-related event that occurs outside the workplace.

Sometimes it is not obvious whether the injury event occurred at the work site or occurred away from work. In such cases the employer should evaluate the worker’s duties and working environment to decide whether or not one or more events at the work place either caused or contributed to the resulting injury, or significantly aggravated a pre-existing condition or injury. In some cases the help of an ergonomist, physician, occupational health nurse, occupational therapist or similarly qualified person may be necessary.

As a guideline, a preexisting injury can be considered to have been “significantly aggravated” when an event at the work site

(a) results in the worker having to be away from work for one or more days,
(b) results in the worker having their work activities restricted to prevent further aggravation, or
(c) results in the worker having to transfer jobs and the transfer would not have occurred but for the occupational event.

An injury is usually considered to be a preexisting condition if it resulted solely from a non-work-related event that occurred outside the workplace.

Signs and symptoms

Employers and workers need to know that redness, swelling and the loss of normal joint movement are the first signs of an MSI i.e. the things that can be seen. Symptoms are what the worker feels but cannot be seen i.e. numbness, tingling, or pain (see Table 14.1).

Table 14.1 Common symptoms of an MSI


Description or Observation

Pain (sharp, shooting or dull) Often the most common feeling, pain may be present at rest or may occur when the person tries to use the injured body part.
Tenderness The area may be painful or sensitive to touch.
Heat or Burning The injured area may feel warmer than normal. The injured person may feel a burning sensation.
Tingling, Pins and Needles, or Numbness The injured person may feel a tingling sensation along the injured area. The injured person may also lose feeling at or around the injured area.
Heaviness The injured body part may feel as if it weights more than normal.
Clumsiness or Weakness The injured worker may drop items frequently or find it difficult to grasp or hold onto objects. The injured person may find it difficult to hold onto things that would normally be easy to hold.
Cramping or Spasm Muscles may stay in a contracted state or contract and relax on their own.

Source: An Ergonomics Guide for Kitchens in Healthcare, Occupational Health and Safety Agency for Healthcare (OHSAH) in BC, 2003.

Stages of injury

Most workers affected by MSIs do not realize that if nothing is done to correct their problems they may be headed for increasing, and potentially devastating, discomfort and disability. There are three stages of injury.

Stage 1

  • Discomfort may persist for weeks or months but is reversible.
  • Most workers experience pain and weakness during work activities but improve on days away from work.
  • Interference with work tasks is minimal.

Stage 2

  • Discomfort may persist for months.
  • Symptoms begin more quickly and last longer.
  • Physical signs may be present, and sleep may be disturbed.
  • Work tasks may be difficult to perform.

Stage 3

  • Discomfort may persist for months or years.
  • Symptoms are always present, even at rest.
  • Activities of daily living are disrupted, and sleep is disturbed.
  • The person is unable to perform light duties at work.
  • The likelihood of recovery is poor.

Worker reports symptoms to employer

The worker reporting symptoms to the employer is what triggers the employer’s obligation to

(a) review the worker’s activities,
(b) review the activities of other workers doing similar tasks, and
(c) identify work-related causes of the symptoms, if any.

The worker can report his or her symptoms to the employer verbally or in written form. The employer may have an injury-reporting process already in place, in which case it should be followed. The worker may provide the employer with documentation from a physician but this is not necessary to trigger the employer’s obligations.

Once the worker has reported his or her symptoms, the employer must review the worker’s activities and those of other workers doing similar tasks. This action serves at least two purposes:

(1) comparing work activities among workers may provide an insight into why the worker is experiencing a problem while other workers may not. Perhaps there are issues related to work station design, equipment use, technique, etc. that might explain why the worker is experiencing symptoms; and
(2) other workers doing similar tasks may also be experiencing symptoms, or may be prone to similar injury, but have not yet gotten to the point that they have reportable symptoms. By reviewing the activities of these other workers, the employer may be able to intervene before they experience symptoms and injuries.

While comparing and reviewing the activities of the injured worker and other workers doing similar tasks, the employer must identify any work-related causes of the symptoms. This is really a hazard assessment that should use an assessment tool or checklist specific to MSIs. An assessment tool appropriate to MSIs is presented in the Safety Bulletin “Musculoskeletal Injuries – Part 5 Assessing Ergonomic Hazards”. Using the assessment tool will help to determine if the causes of the symptoms are work-related. The help of an ergonomist, physician, occupational health nurse, occupational therapist or other professional knowledgeable about MSIs may be needed to help the employer with this review, identification and assessment of work-relatedness.

Many checklists and assessment tools are available from a variety of sources. The recommended assessment tool is one that was introduced in May 2000 by the State of Washington, Department of Labor and Industries, and is now also being used in British Columbia. The use of similar hazard assessment tools that are equally effective is acceptable.

Risk factors

Three major factors that involve how a worker’s body functions during work contribute to MSIs. They are awkward body positions, excessive force (forceful exertions) and repetition.

Awkward body positions

Awkward body positions are often the result of the location and orientation of the object being worked on, poor workstation design, product design, tool design or poor work habits (see Figures 14.43 through 14.49). Less-than-optimal postures such as leaning forward from the waist for extended periods of time, or bending the neck downwards at an exaggerated angle, can load muscles with “static work”. Static work involves muscles being tensed in fixed positions and over time, becoming tired, uncomfortable, and even painful.

Figure 14.43 Raising and tilting the bin can eliminate an awkward posture

Figure 14.44 Placing the conveyor closer to the worker reduces excessive reaching and an extended body position

Figure 14.45 Example of heavy, static work

Figure 14.46 A raised work platform can eliminate an awkward posture

Figure 14.47 A wheeled footstool can make awkward work comfortable

Figure 14.48 A tall, tilting table eliminates an awkward work position

Figure 14.49 An elevated work platform reduces awkward overhead reaches

Forceful exertions

Forceful exertions (excessive force) may overload muscles, tendons and ligaments. Forceful exertions are commonly used when lifting, pushing, pulling and reaching. A packer on an assembly line for example may often use a highly forceful grip to assemble a lightweight item or lift a box or carton, especially if it is slippery or difficult to grasp. Awkward wrist and arm positions may also contribute to the problem (see Figures 14.50 and Figure 14.51).

Figure 14.50 A bent tool eliminates an awkward wrist position and provides good grip

Figure 14.51 Electric scissors can eliminate the high hand forces required to cut thick material


Repetitive movements eventually wear the body down. Without sufficient time to recover between repetitions, muscles become tired and may cramp. Other muscles try to help but may also become tired, cramp and become injured.

How quickly this happens depends on how often a repetitive motion is performed, how quickly it is performed, and for how long the repetitive motion continues. Repetitive work is more of a problem when it is combined with awkward body positions and forceful exertions. A worker who packages a small product day after day or who uses a stapler or power nailer to assemble wooden frames are examples of workers performing repetitive work.

Subsection 211(b)

Once the assessment has been completed and if the causes of the symptoms are work related, then the employer must eliminate or control the causes to try to avoid further injuries. Suggestions for eliminating and controlling MSI hazards can be found in the Safety Bulletin “Musculoskeletal Injuries – Part 6 Reducing Ergonomic Hazards”.

For more information
Wrist Splints and MSIs
Bulletin ERG025
How to Use Wrist Rests
Bulletin ERG029
Proper Height of Work Surfaces
Bulletin ERG016
Anti-Fatigue Matting
Bulletin ERG005
All Shook Up – Understanding Vibration
Bulletin ERG026
Selecting Hand Tools
Bulletin ERG023
International Format for Material Safety Data Sheets
Bulletin LI011
Exercise Balls Instead of Chairs? Maybe Not.
Bulletin ERG036
Fatigue and Safety at the Workplace
Bulletin ERG015-1
Fatigue, Extended Work Hours, and Safety in the Workplace
Bulletin ERG015
Focus on Human Performance Part 1: Sleep Inertia
Bulletin ERG034
Focus on Human Performance Part 2: Working in the Cold
Bulletin ERG035
Good Product Design – Avoiding the Average
Bulletin ERG030
New Thinking About Carpal Tunnel Syndrome
Bulletin ERG039
Preventing Lower Back Pain
Bulletin ERG038
Push It or Pull It?
Bulletin ERG033
Putting the “I” in Ergonomics
Bulletin ERG040
That Hurts! Contact Stress at Work
Bulletin ERG032

General information about MSIs

Ergonomics – Workers’ Compensation Board of British Columbia (WorkSafe BC)
Typing Injury FAQ
Back to Basics – A guide to good health
WCB – Alberta
Occupational Overuse Syndrome – Guidelines for Prevention and Management
Department of Labour, New Zealand
Occupational Overuse Syndrome – Checklists for the Evaluation of Work
Department of Labour, New Zealand
Aching arms (or RSI) in small businesses
Health and Safety Executive, United Kingdom
Fitting the Task to the Person: Ergonomics for Very Small Businesses
California Department of Industrial Relations
The Learning Zone – Ergonomics 4 Schools

Office ergonomics

CSA Guideline Z412, Guideline on Office Ergonomics
Canadian Standards Association
Office Ergonomics Training
Typing Injury FAQ
Office Ergonomics
WCB – Alberta

Health care industry

An Ergonomic Guide for Kitchens in Healthcare
Occupational Health & Safety Agency for Healthcare in BC
An Ergonomics Guide for Hospital Laundries
Occupational Health & Safety Agency for Healthcare in BC
Musculoskeletal Injury Prevention Program (MSIP): Implementation Guide
Occupational Health & Safety Agency for Healthcare in BC