Pain in the Workplace

Work can cause pain. Any strong effort exerted over a long time usually causes some degree of pain, or at least discomfort. This is natural. Usually the tissues strengthen with mild overuse. This was first noted in bone by J.Wolff and reported in 1872. Now it is referred to as Wolff's Law. But we also know that too much overuse, e.g., repeatedly bending a bone, can cause stress fractures. The same is true of all tissues. Muscles and tendons become thicker and stronger with use, but if those same stresses that cause them to become stronger are applied to excess, the tissues break down, and now we have an injury. Such an injury is often called a repetitive strain injury (RSI) or cumulative trauma disorder (CTD).

How Much is Too Much?

No one really knows for sure. Guidelines are at this very moment being worked out....in the midst of great debate. But at least we can agree that certain conditions at work may present risk of injury to susceptible individuals. These are called "Risk Factors".

Unfavourable Working Conditions and Their Potential Effects.

These health effects are based upon epidemiologic studies and the presence of the risk factor increases the risk of an individual developing a chronic work-related musculoskeletal injury. All potential health effects depend on the length of exposure to the conditions, the magnitude or size of the stressor, and the variation of the exposure.

So this is what can happen. But how, you may ask, can anyone tell what really has happened in a particular individual? Now we come to the need for a tissue diagnosis.

Making a Diagnosis.

This can be done by anyone with sufficient knowledge. You don't have to be a rocket scientist. You don't need a degree in medicine. You do need a good knowledge of anatomy or you can refer to charts like the one that follows, prepared by one with an excellent knowledge of anatomy. The diagnosis is based on knowing where the pain is, what makes it worse, and where tenderness (pain on touching) is located.

Differentiating Sources of Neck/Shoulder Pain

The above indicates how this is done with neck and shoulder problems, and is only a beginning. There are, of course, many other tests that need to be done. They are described in the book from which this table is taken. We can do the same thing with elbow pain.

Differentiating Causes of Pain in the Elbow/Upper Forearm

Myalgia

This means simply "muscle pain" and has appeared several times in the tables above as though it were an overuse problem. But not everyone accepts that muscles can become become injured through repetitive use, and those who do not, assert that pain in muscle is either fatigue from unaccustomed work (and will go away in time with rest), or is imagined. They cannot believe that muscles can be damaged from low level activity. However recent reports from Scandanavia have reminded us that even with very low level activity for prolonged periods, injury to some fibres can be expected. This is because only those muscle fibres that are most sensitive to nerve stimulation are recruited for activity then...they do not share this load on a rotating basis as we might expect...and when a stronger force is required they continue to be active.

These hard working muscle fibres are referred to as cinderella fibres. The figure below shows this in graphic form. The references and a fuller description of this phenomenon are found in the book described above.

Another factor to consider is that intramuscular pressure can rise during muscle contraction to such a level that it blocks the inflow of blood. This is easily demonstrated in a muscle that is in a fascial compartment as the supraspinatus muscle is.

Mechanisms Involved in Myalgia Development include:

• Motor Control, i.e., recruitment ... as above
• Intramuscular Pressure, if a muscle lies in a compartment... as above, or
• Muscle Blood Flow Reduction for other reasons, such as muscle contraction itself, and sometimes granulocyte plugging of capillaries.
• Metabollic Crises involving lowered pH, and ion shifts such that there is too much calcium inside the muscle cells and too much potassium outside.
• Free Radical Formation ... as well as
• Mechanical Forces such as tension, shear and friction.

  There is much more that needs to be learned and research is in progress.

Psychocial Factors

These are also important, as this diagram indicates.

For More Information

contact The Institute for Work and Health or

The Canadian Injured Workers Alliance.

You can even read a book about this subject.

Perhaps you might enjoy an academic description of the anatomical basis of pain.

If you know of other on-line sources that you would like to recommend, please E-mail them to me, Don Ranney, so I can add them here.

Where does he come from?

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Created by: ranney@hsfx.ca 1997/03/29
Revised by: ranney@hsfx.ca 2011/03/14