Repetitive strain injuries or RSIs are now the single largest cause of occupational health problems in the United States . RSIs can occur in any activity requiring repetitive motions, but most often affect those in occupational settings. Several theories exist as to why an RSI occurs. Some include the concept that because muscles and tendons get blood through capillaries that pass among the muscle fibers, tensing a muscle repeatedly restricts its blood flow. Theoretically, by the time you're exerting 50% of your full power, you're completely restricting your blood flow. Without fresh blood, your muscles use stored energy until they run out, then they switch to anaerobic (without oxygen) metabolism, which generates by-products like lactic acid, which cause pain.

This particular theory actually makes little sense. Lactic acid for instance is a by-product of the normal metabolism, not a waste product. Lactic acid does not cause muscular pain either, this is caused by muscle ischemia due to heavy lifting and fatigue, something a repetitive stress injury employee does not experience. Nonetheless, according to the theory, more tension means less blood flow, and the cycle continues, even though the same symptoms are not experienced by seasoned weight lifters.

Another theory is that, due to repetitive motion, some muscles may be fatiguing while other muscles are compensating or overworking while they try to maintain the function of the fatiguing muscles. Since the muscles meant to do the work are not functioning properly, either as a result of acute injury, or from fatigue due to long-term overuse or micro-trauma, the neighboring muscles (or another muscle group) may be recruited to "help out" or take over completely. These muscles quickly fatigue because they are not designed to do the job and thus fail to support joint function.

Another theory is that the repetitive motion causes too much wear and tear over an extended period of time leading to micro-injury and eventual failure of the muscle and its surrounding tissue. This theory, while plausible is only likely as a by-product of repetitive motion, not due to the repetitive motion itself.

Resistance strength training restricts blood flow and athletic level cardiovascular events produce lactic acid with no side effects. These athletic events are also repetitive in nature and cause the fatigue of muscles. Runners perform repetitive motion, they run hundreds of miles a month, but they suffer few of these side effects. In many cases the first symptom of an RSI injury is pain, not fatigue and this is also contrary to normal body physiology. What is most compelling is that the physiological reasons given for an RSI should by definition affect everyone involved in any repetitive type of motion. But only a few people are affected, leading us to consider that other mechanisms are likely at work.

Unlike strains and sprains, which usually result from a single incident, RSIs develop over time. That's why RSIs are also called Cumulative Trauma Disorders (CTD). RSIs can affect almost any part of the body, but they often occur in upper body. The most commonly affected body parts are the fingers, hands, wrists, elbows, arms, shoulders, back and neck.

The symptoms of an RSI are varied; yet one or more of the following symptoms will be present in the injured area:

  • Aching
  • Tenderness
  • Swelling
  • Tingling or numbness
  • Loss of joint mobility
  • Weakness
  • Loss of coordination
  • Joint crepitus
  • Muscle spasms
  • Decreased coordination

These symptoms may appear in any order at any stage in the development of the injury. Symptoms may occur at any time during work, immediately after work or many hours (or days) after work. Many people first experience symptoms when they are not working. For example, an injured worker may have no pain at work and wake up in the night with a painful shoulder or elbow.

There are many types of repetitive strain injuries because many different parts of the body can be affected. Carpal tunnel syndrome is the most well-known RSI, but it is not the most common. Other repetitive strain injuries include: tendonitis, tenosynovitis and rotator cuff injuries.

We all know that the human body functions as the sum total of all its parts working in synergy. No one individual muscle is solely responsible for any joint motion. Even the simple action of reaching overhead uses at least seven joints associated with shoulder motion. Movement can be considered to be caused by the integrated function of all muscles used in a specific kinetic chain of motion and, as such, all motion is dependent on the muscles in that chain to function as a unit. But, like any chain, if one link is weak or overstressed, it is likely to affect the entire kinetic chain and movement.

Your body is dependent upon all of your muscles and how they function around the joint that they pull on. Let's take the knee for instance. The integrity of the knee joint is based on the combined effort of the quadriceps, which pulls up, the hamstrings, which also pull up, but which need to be pulling in a 3:1 ratio to the quadriceps; the gastrocnemius muscle, which pulls down, and various other muscles that support the knee laterally. All of these muscles and some others create a perfectly balanced tension scale around the knee joint allowing that joint to function as a hinge joint in its various day-to-day functions.

Sometimes, a part of a muscle will get out of balance and begin to affect the entire integrity of that joint. When this happens, the joint does not track appropriately, additional wear and tear occurs and injury follows. An example might be in injuries such as patella-femoral syndrome (chondromalacia). When the vastus lateralis muscle becomes stronger than the vastus medialis. The patella will track to the outside of the knee and the wear and tear will cause knee problems. This is a widely accepted phenomenon in chondromalacia, but what if this example was true to all joints that developed muscular imbalances?

An RSI, by nature is a repetitive motion based injury. Repetitive motions cause the development of certain muscles over the development of others. Should this repetitive motion lead to the development of a muscular joint imbalance, which leads to joint tracking problems, leading to excess wear and tear and injury; then the RSI can now be described not as a repetitive stress injury, but as a muscular imbalance injury. Since the imbalance would effect all motion of that joint whether the person was at work or not, then the injury could well develop at any time. It may also not be work related, but work site induced.

Think of the muscular imbalance as the development of a tug of war between the muscles, which surround a joint. If one side becomes stronger, it will overpower the joint and cause imbalance, causing excess wear. One of the most common injuries in an RSI is back injury. Normally the injured person is bending over and twisting when lifting an object. Imagine now that in this position the hip flexors are shortened and being engaged to stabilize the legs and pelvis for the repetitive movement. As the employee begins to develop strength in this motion, the hip flexors overdevelop, pulling the spine into a hyperlordosis and anteriorily tilting the pelvis at the same time. This causes a shift in the lumbar vertebrae causing stress to be unevenly distributed over the intervertebral discs. This places unbalanced pressure on the discs and causes the lumbar muscles to work harder to compensate for the imbalance, all day long. Back pain follows.

The common problem associated with an RSI may be better approached as an imbalance injury versus a repetitive stress injury. Of course it could be argued that the end product is the same thus the treatment should not necessarily be changed; however, if the imbalance is not corrected any treatment of the RSI could lead to chronicity and unnecessary surgical intervention, greatly increasing health care and insurance costs. That being the case, perhaps treatment should also include corrective exercise.

What to Do with Your Clients
Step 1: You need to be aware of your clients occupational movement patters. Any continuous position, including sitting, can place the body into a position of imbalance. So do not be too quick to dismiss your executives because all they do is sit. Could be the sitting has forced a shortening of the hip flexors, leading to the same problems associated with a conveyer belt worker who is lifting repetitively.

Step 2: You will need to evaluate the client's posture and gait. Your first assessment should be posture. Are their shoulders and hips level, is their back well positioned, their neck not too far forward. Are their arches dropped? Are the feet pronated or supinated? Take note of these problems before going on to step 3.

Step 3: Do a gait analysis. Watch them walk. Do they swing both arms equally? Do they walk on their toes or flatfooted? Are their feet and knees aligned? Does their pelvis move with the motion or is it locked? Is there a limp or a posture problem? Do a slow and a fast walk and compare the two. What changes do you see?

Step 4: Do a NIHS BOSU ball posture and balance assessment. Note the stability of the ankles, knee grind, hip motion and position. Does the client complain of painful or burning arches? Does the pelvis tilt? Is the back curve lost or increased? (More information on this test is available through the NIHS level I and II certification program).

Step 5: Assess the client's balance. Do they have a strength based balance issue or is it occulovestibular? To assess this, check the balance on one leg versus the other. Is there a difference? Have they had any middle ear infections or problems? Does the stability improve after spinning in a circle or remain the same? This will determine whether you are dealing with an ear based balance problem versus a strength based balance problem.

Step 6: Chose the appropriate exercise prescription. Fixed resistance training equipment may likely increase the problem and advance the condition. While it may be necessary to use fixed equipment in some cases, the best equipment, by far, is equipment that fully integrates body motion and thus promotes synergy. Equipment, such as FreeMotion, Keiser Infinity and certain LifeFitness pieces, are well designed for this purpose and lend themselves well to progressing the client through proprioceptively enriched strength-balance based protocols. FreeMotion is perhaps the best suited to these protocols due to their design and cable length.

In using functional strength training equipment begin by emphasizing the opposite motion that the client may be engaged in at work. But do not ignore total body integration. The human body was designed to function in all three planes of motion, using all muscles simultaneously. Promoting full body exercise from a position of stability to a position of instability is by far the most superior approach to working with such clients.

Finally, be aware the client's preexisting condition. It is likely that some micro-damage has occurred and thus the client has an increased risk of injury. Begin slowly. Work the foundation of balance before progressing to resistance training. Never progress the client too fast and use SOAP notes to help you to assess changes in pain perception, function and posture.

Keith Spennewyn, MSc, FNIHS, is President and owner of the NIHS, a personal training certification corporation focusing on preparing certified trainers for the future. For questions, email him at



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