Ergonomics

Repetitive Strain Injuries

Article in New England Pen, a publication of Computer Sciences Corporation, Fall 1993.

Your big programming project is almost due and you are doing a lot of stressful programming and debugging trying to get the work done. You have been doing substantial overtime for weeks, maybe months, when suddenly your productivity drops precipitously. You have sharp pains in your wrist and numbness in your hand and fingers. The pain gets worse and you miss more and more work days. Your doctor indicates that you have injured the tendons in your wrist and prescribes an extended period of time off to allow the injuries to heal. To recoup the lost time and income you file a Workers' Compensation claim.

This scenario is becoming increasingly common in a business world where computers are becoming a part of more and more jobs and not just for programmers. People suffering from cumulative trauma disorders (CTD) also called repetitive stress or strain injuries (RSI), are demanding compensation for lost ability to work, pain, and suffering. Products claiming to prevent "carpal tunnel syndrome", a type of RSI, have cropped up in many computer stores and are hyped in most trade journals.

RSIs have become a constant part of our business culture because the incidence rate and costs of RSIs have increased dramatically over the last decade. In 1981 RSIs accounted for just 18% of occupational illnesses nationwide. By 1990 it had increased to 56%. At an average of $5000 to $10,000 per case, estimates for the annual cost of RSIs in Workers' Compensation, medical bills and lost work-days range from $20 to $27 billion.

Given the escalating costs of RSIs, we need to understand what RSIs are and how they occur. Hours of typing at the computer involves constant repetitive motion, putting continuous stress on the wrists, elbows and shoulders, which accumulates over time. Tendons in the arm become enflamed, squeezing nerves resulting in numbness and pain and sometimes permanent damage to nerves in the hand, wrist, or shoulder. Collectively, these types of problems are called RSIs. That is, RSIs are a general category of ailment that are related to several specific types of injuries resulting from prolonged repeated performance of physically stressing activities. Carpal Tunnel Syndrome is the RSI currently most commonly known by the public, but is actually relatively rare. Tendons, blood vessels and the median nerve pass through a narrow area in the wrist, surrounded by the carpal bones. When tendon swelling occurs here, it may pinch the nerve. Several types of Tendinitis are less well known by the public, but are much more common. Tendinitis is when friction in the sheath shrouding the tendons causes it to become enflamed and painful. Finally incorrect hand positions may overload arm muscles and fascia which may cause inflammation leading to muscle shortening and scar tissue formation.

While, in general, the conditions which bring on RSIs are long hours at a single task involving a constantly repetitive motion, the precise conditions that induce these injuries are not well known. Researchers believe that each individual motion creates a micro-trauma which under normal conditions would heal without a problem. The repetition of the motion inhibits the healing process as the same tissue is traumatized repeatedly, allowing an accumulation of injury to occur. Even though the precise characteristics of tasks causing these injuries is not known several contributing factors have been identified.

Perhaps the most significant factor contributing to RSIs is poor ergonomic design of the task environment and tools used to perform the task which create poor posture and body mechanics. Poor posture and body mechanics result in the unnatural physical stresses which eventually cause injury. Significant features of the task environment for computer related tasks include: (1) chair height, seat angle, and back angle, (2) keyboard height and angle, (3) screen height, angle, and reflected glare, and (4) reference document height and lighting.

In addition, the currently popular design for keyboards is poorly suited to the task of typing. The design positions the hands close together in front of the body, forcing the user to angle his or her forearms in; in turn, the wrists must head out slightly to line up the finger's on the home keys. This strains the tendons that run through the wrist and connect the fingers to the muscles of the forearm. The rows of keys are staggered, causing unnecessary reaching to the left and right. Some researchers believe that the palm-down attitude for typing may be wrong, increasing the amount of strain. Software tools may contribute too, by requiring repetitions of certain keystrokes or key-chords (combinations of keys held together) significantly more often than others. Psychological stress is believed to be another significant factor. Stress may contribute by creating muscle tension, which reduces blood flow to hard-working muscles and tendons; without enough oxygen, these tissues become fatigued and prone to injury.

In addition to the changes in work assignments and lack of correct equipment that specifically contribute to the injuries themselves, there are various socio-political factors that contribute to the growing phenomenon of job-related RSIs. Progress in preventing and treating RSIs is hampered by the lack of available high-quality literature documenting the complex interplay of force, posture and repetition involved in manual work in the office. Given the medical community's reluctance to attribute the injuries to work-related tasks, getting accurate diagnoses is difficult and sufferers often go from doctor to doctor seeking relief. With the conflicting diagnoses, appropriate and effective treatment may be difficult to obtain. To fight the increasing number of worker's compensation claims, some employers and industry organizations have advocated and used medically dubious tests and treatments, such as dispensing vitamin B6 tablets, applying hot compresses to already inflamed areas, and requiring that employees keep an injured joint immobilized while continuing to work, practices that may expose the employee to additional injuries.

Legitimate treatments vary widely in invasiveness and effectiveness. They include enforced vacations where work-like tasks are not allowed, physical therapy, cortisone injections, and in extreme cases, surgery. However, most experts agree that the best alternative is prevention, primarily effected through redesigning the task and work environment based on available ergonomic principals. The two cornerstones of this redesign effort are flexibility of the work environment, and breaking up the work task over time to reduce the number of successive repetitions of potentially harmful motions.

Most experts agree that three points of contact are the primary concerns in preventing RSIs: where your eyes meet the monitor screen, where your fingers press against the keyboard, and where your body rests in its chair. While there is not universal agreement on the best work environment for computer tasks, there are some widely accepted principals:

	reduce screen glare by reducing overall lighting, using diffuse overhead lighting supplemented by localized task lights
	the optimum height for a screen monitor is such that the top of the screen is at eye level
	monitors should be equipped with a tilt-swivel stand to allow adjustment to the proper height and to allow occasional variation
	keep reference material at the same distance from your eyes as the monitor screen so you don't have to shift focus every time you check the reference material
	the keyboard should be positioned to provide the naturally strait position your wrists take on in relation to your arm when you stand relaxed with your arm dangling at your side. In addition, your arms should be in a relaxed position at your sides with a 90-degree or slightly larger bend at the elbow. Typically this will require that the keyboard be equipped with a drawer or special platform to allow it to be positioned 3" to 5" below standard table height
	While conventional wisdom indicates that you should sit straight up with your feet firmly flat against the floor, there is considerable doubt that this is best for computer users. In situations where adjustable chairs are available, VDT workers observed in a study preferred to lean back so that their bodies were at angles between 97 and 121 degrees.
	chairs should provide good upper and lower back support and sufficient adjustment to allow the user to find a comfortable position
	knees should be positioned slightly lower than the hips. So the chair seat should be tilted slightly forward to assure proper knee position
	feet should be able to be firmly planted on the floor (although need not be so continuously). An adjustable footrest should be provided for shorter people to allow them to attain the proper foot position.
	warm-up exercises can prevent injuries: gently massaging the hands; pressing the palm down to stretch the underside of the forearm; pressing the fist down to stretch the topside of the forearm. Each position should be held for at least 10 seconds
	frequent short breaks from work are crucial to allow eyes to rest from fixed focus and to allow hands and arms to recover and relax.
	the warm-up exercises should also be used, at a minimum, for a few minutes each hour

RSIs are becoming increasingly prevalent in the computer industry and other businesses that rely heavily on computers. Despite lack of actual regulations, there is increasing government intervention through fines and penalties when significant problems are not resolved. With the increasing human and fiscal costs of RSIs, companies have been, and should be, taking serious steps to combat these debilitating injuries.