Ehlers-Danlos National Foundation

This is the first of a three–part series on the recognition, evaluation, and control of potential risk factors that can lead to increased injury, discomfort, and/or fatigue. This issue discusses each of the seven potential risk factors so you can recognize them in any situation. It will also provide guidelines to determine the severity of the risk. Part 2, which will be presented in the next issue of Loose Connections, will explore the variety of control methods available to reduce or eliminate the potential risk factors introduced here.

The word Ergonomics comes from the Greek "ergo" and "nomos" which translated means "work" and "study of" or "laws of". Thus, ergonomics is simply the study of or laws of work or of the relationship between people and their work environment. The definition used by the Occupational Safety and Health Administration is more specific: "adapting jobs and workplaces to the worker by designing tasks, tools, and equipment that are within the worker's physical capabilities and limitations". Ergonomics, however, is not limited to the workplace. It is a multidisciplinary science that includes the fields of medicine, physiology, anatomy, engineering, psychology, chemistry, and biomechanics just to name a few. So how can Ergonomics help people with Ehlers–Danlos Syndrome?

Many of us have probably heard the term Ergonomics used as an adjective in various TV commercials and print ads. It is especially common when describing cars. An ergonomically designed interior and ergonomic displays and controls. What these ads are referring to is analogous to the terms "perfect fit or fits like a glove". Thus, Ergonomics aims to be user friendly by designing things that are easy to operate both mentally and physically while also requiring the least amount of energy and effort. Ideally, objects requiring strength and precision would be designed for the least able people in society, usually the elderly and disabled populations. Unfortunately, as many of you can attest to, there are far too many heavy doors and poorly designed items currently in use. The good news is that manufacturers, engineers, designers, etc. are much more aware of these issues and are starting to incorporate ergonomics into their products.

Risk Factors and Potential Stressors

In order to design or choose ergonomic related items, we must first understand what potential risk factors and stressors need to be reduced or avoided completely. We must also realize that buying an ergonomic tool does not guarantee an ergonomic fit. Many items are labeled as ergonomically designed, but really fall short of this distinction. Likewise, the tool or item must be correctly matched with the intended use or one will not benefit from choosing an ergonomic item and can even make things worse. There are seven major risk factors or potential stressors. They are as follows: repetitive motions, awkward postures, forceful exertions, mechanical stress (direct pressure on nerves and soft tissues), vibration, extreme temperatures (both too low and too high) and the use of ill fitting or poorly chosen gloves. The more risk factors present, and the more severe each risk factor, the higher the potential for injury or discomfort.

The evaluation of severity mentioned below with each risk factor is just a guideline. It is impossible to exactly predict injuries and to avoid all potential risk factors. Therefore, your mission (should you decide to accept it) is to reduce as many risk factors as possible and to limit the severity of each one. Even when only one severe risk factor is present, the goal is still to reduce it as much as possible within financial constraints and current knowledge.

A detailed discussion of possible control measures for each risk factor will be presented in the next issue of Loose Connections as Part 2 of this article. The important thing to remember, is that Ergonomics, like Medicine, is as much an art as a science. You know your bodies the best, so you need to consider what feels good to you. One caution though: some postures – like slouching – may seem comfortable at first, but can lead to injuries and discomfort in the long run.

Repetitive motions are one of the most common risk factors and are often blamed for many workers' and hobby enthusiasts' injuries. In fact, there are numerous names for repetitive related disorders. These include repetitive stress injuries (RSIs), cumulative trauma disorders (CTDs), and overuse syndromes. Tendons, muscles, nerves, ligaments, blood vessels and bursa are often affected. Carpal Tunnel Syndrome (CTS), sometimes referred to as writer's cramp, is perhaps the best known CTD. It is caused by compression of the median nerve in the wrist area and can occur from chronic irritation and swelling of the nearby tendons as well as direct pressure on the nerve. See section on Mechanical Stress.

Most jobs, school, and home tasks involve some repetition. There is no known dose response relationship, so we do not know exactly how much repetition is too much. However, we do know that there is a higher incidence of injuries in highly repetitive jobs. When other risk factors are also present, the risk increases even more. As a guideline, a motion is considered highly repetitive if the cycle time is less than 30 seconds. This means that more than one lift, step, exertion, or motion occurs in 30 seconds.

Awkward Positions

Most EDSers are very familiar with awkward postures. In the world of ergonomics, we actually have ways of evaluating the severity of these postures. We all have a neutral posture that is the least stressful and most powerful position for each of our joints and our entire bodies. The more we deviate from these positions, the greater the risk.

For standing postures, neutral is with arms close at the side either straight or at a right angle (90 degrees) with the wrist in line with the forearm. For sitting postures, the upper body is the same as with standing, but feet should be flat on the floor with legs at approximately a 90 degree angle. Thus, neutral basically means arms close to the body with elbows either straight or at a right angle and the wrist straight. If the legs are involved, they too should be at a right angle, but the feet must touch the floor or a footrest. They should never be left dangling (for those short people like me whose feet never seem to touch the floor!!!).

The further you move away from neutral, the greater the risk. For example, a severe risk for the wrists would consist of bending them as far forward or backward as they go, as well as rotated out to either side. So if you type and look down at your wrists, they should be in line with the forearm. If they are bent as far as they go either backwards (extension), or forward (flexion) that constitutes a severe awkward posture. See wrist diagram. If hands are slightly bent or moved to the right while typing, that is a minor awkward posture.

The same can be said for every part of the body. The neck, for example, should not be bent forward or backward or tilted to the side. The same goes for the back except you should also avoid twisting motions. In addition, there is a special type of awkward posture known as a static posture. This occurs when a body part is not moving, but is still doing work. Thus, if you hold an object in your left hand while using your right hand to work on it, the left hand is subjected to a static posture. Likewise, holding your arms above shoulder level requires several muscles to work even though the arms may not be moving. People recover much slower from static postures than dynamic movements. This is in part due to the buildup of lactic acid that occurs in the static body part.

The key to determining severity of an awkward posture is how far the joint is away from the neutral position. Most of us will always have some awkward postures in various joints. The idea is to reduce the extremes as much as possible and limit the amount of time the joint is not neutral. Stay tuned for Part 2 in the next issue of Loose Connections to find out how.

Forceful Exertions

What constitutes a forceful exertion? You may be surprised by the answer. While it is difficult to use an exact number to determine the severity of an exertion, simply holding a pen too hard or banging on the keyboard can be considered forceful. Of course, if you lift 50 pounds or more, that also constitutes a forceful exertion. For many of us, lifting only 5 pounds may be forceful.

Computer programs are often used by ergonomists and biomechanical engineers to analyze the stress on each of the joints. For any given exertion not all joints suffer the same amount of stress. In depth analysis to determine whether force is a risk factor is not really necessary in people with EDS because almost everything can end up being forceful. Thus, we should always strive to limit the amount of weight we carry.

Anytime we use our smaller, weaker, muscles (like those in our forearm commonly used when we pinch objects), will result in a more forceful exertion than if we use the larger, stronger muscles in the upper arm. Likewise, the reason we lift with our leg muscles and not our back muscles is that leg muscles (especially the quadriceps) are one of the strongest muscle groups in the body. Back muscles generally are much weaker.

Mechanical Stress

Ever leaned on your elbow and your entire arm went numb? That's what the risk factor mechanical stress is all about. Direct pressure on sensitive areas of the body. The most common places where this occurs are at the elbow, wrist, fingers and back of the knees (usually by or on the popliteal artery). Activities often associated with direct pressure on nerves or soft tissues include leaning on a sharp desk edge while writing or typing, sitting improperly, wearing constrictive clothing, using standard, poorly designed scissors, taking your frustrations out on a helpless stapler or hole punch and using body parts as tools (hammers, in particular. Don't laugh. It happens more than you think!!). If we do this over a period of time, nerve damage and other soft tissue injuries may occur.

Vibration (Whole Body and Segmental)

There are two main types of vibration: whole body and hand/arm or segmental. Whole body vibration affects the entire body. The main exposure for most of us would be riding in a car or truck unless we happen to work on a vibrating platform. Fortunately, today's cars and trucks have built–in dampening protection and provide much smoother rides. Segmental vibration occurs in one part of the body and is most common when using power tools.

Raynaud's phenomenon, also referred to as Hand–Arm Vibration Syndrome or White Finger, is often caused by exposure to hand/arm or segmental vibration. This disorder affects the small blood vessels in the fingers and can cause significant pain and loss of feeling. Raynaud's is characterized by recurrent episodes of finger blanching due to closure of the arteries in the fingers (digital arteries). Symptoms include "intermittent numbness and tingling in the fingers, skin that turns pale, ashen, and cold; and eventual loss of sensation and control in the fingers and hands".

Vibration has other effects as well. People who use vibrating tools often have to grip harder to maintain control, thus adding a forceful exertion as a risk factor. You only have to watch a construction worker using a jack hammer to see how vibration affects their bodies.

Extreme Temperature (Cold and Hot)

Cold temperatures can often aggravate Raynaud's and cause muscles to tighten up. Bundling up to keep warm can keep out the cold, but wearing layers of clothing can also decrease range of motion and increase the likelihood of injury. Gloves in particular can be a substantial problem if they are not chosen carefully for the type of activity and/or they do not fit well. See section on Poorly Fitting or Poorly Chosen Gloves.

Many people are also adversely affected by cold in various other ways. These include breathing problems, fatigue, dexterity, sensory sensitivity, and grip strength. For those of us who live in arctic weather, we are also subjected to icing conditions which impair our coordination even more than normal and can result in near misses, severe slips, and falls. Both can cause substantial injuries. Needless to say, we should limit the amount of time in very cold temperatures and if we do venture outside, we must be properly clothed and have some type of support.

Extreme heat, especially in conjunction with high humidity, is tough on anyone. Disabled people and the elderly tend to be affected even more. Besides the possibility of heat cramps, heat exhaustion, or heat stress, hot and humid weather can be extremely fatiguing. Avoid very hot weather whenever possible.

Some people with EDS appear to be sensitive to the direct sun and should try to avoid or limit exposure. Even those that don't have EDS should keep in mind that certain medications, such as tetracycline, can cause sun sensitivity even in "normal" people.

Poorly Fitting or Poorly Chosen Gloves

Gloves are often necessary and can be protective. However, when we choose the wrong gloves or they do not fit well, they become potential risk factors or stressors. Most gloves add bulk and can actually increase the amount of force necessary to do a task. For example, try wearing gloves while writing. Even thin ones can cause you to use more force than without gloves. Likewise, gloves can interfere with the ability to feel and therefore, can throw off your ability to judge how much force is needed. If gloves are too small, they can actually cut off circulation and increase fatigue. If they are too large, they can interfere with tactile ability and add force, another risk factor, to your task.

The most common risk factors you will probably encounter on a daily basis are repetitive motions, awkward postures, forceful exertions, and mechanical stress. These also tend to be more significant risk factors than the other three mentioned above. Remember, the more risk factors present and the more severe each risk factor, the greater the possibility of injury or discomfort. Thus, it is imperative to try and avoid, reduce, or eliminate the most severe risk factors and to lessen the number of total risk factors present. Does this seem like a daunting task? After all, how can a mere mortal reduce or eliminate problems as diverse as repetitive motions, awkward postures, forceful exertions, mechanical stress, vibration, extreme temperatures, and ill chosen or poorly fitting gloves? Stay tuned. Same newsletter. Next issue. Why? Because the next issue's article will answer the all important question: How to control these risk factors in the home, at work, and in school.

References

U.S. Department of Labor, Occupational Safety and Health Administration, Ergonomics: The Study of Work, 1991, pp. 1–19.

Vern Putz–Anderson, Cumulative Trauma Disorders: A Manual for Musculoskeletal Diseases of the Upper Limbs, 1988, Taylor & Francis, pp. 1–25.

Thomas J. Armstrong, "Ergonomics and Cumulative Trauma Disorders," Hand Clinics, Vol. 2, No. 3, August 1986, pp. 553–565.

U.S. Department of Labor, Occupational Safety and Health Administration, Ergonomics Program Management Guidelines for Meatpacking Plants, 1990. pp. 1–10.