Basic office activities involve sitting in front of a computer terminal and operating it by means of typing or moving a mouse. Still, no matter how harmless these activities may seem, they do set the stage for injuries that can develop over time. While these activities are not particularly hazardous for a worker who does them only occasionally, the situation becomes more critical for those who have no choice but to sit in front of a computer screen and type for long periods every working day.
It is very important to know that musculoskeletal injuries (MSIs), and specifically, repetitive motion injuries (RMIs) rarely originate from one event or a particular factor. As a rule they develop over time from a variety of factors. Some factors are strictly work-related and beyond the workers' control. On the other hand, the workers themselves can have some control on other factors, such as their individual work practices. Other things like body build, age, gender, some medical conditions, types of personality, attitudes and life style can also contribute to RMIs. No matter that such factors may be beyond any control, becoming aware of them is nevertheless important.
Work-related factors that present the greatest risk for MSIs involve:
- fixed and constrained postures that are frequently awkward, uncomfortable and maintained for too long a time,
- repetitious and forceful hand movements,
- a high pace of work,
Because the human body was designed to move, it cannot tolerate immobility for long. Merely sitting at a desk for long times can be unhealthy and damaging to the musculoskeletal system. Holding the upper body still in an upright position requires a lot of muscular effort and contributes to what is called a static load. That is the invisible but constant battle against gravity and fatigue, and injury is the price.
Both holding one's head at the optimum distance from the screen and document holder and maintaining one's arms in the proper typing position increase the static load on the whole upper body, and on the neck and shoulders in particular. The reduced blood supply that follows not only accelerates fatigue, but also leaves the musculoskeletal system susceptible to RMIs. To make matters worse, the furniture in most offices does not fit the worker either because it is not adjustable or, where it is adjustable, workers are not properly instructed on how to adjust it.
Poor posture can be a result of:
- Non-adjustable or otherwise unsuitable workstations;
- The layout of the workstation is inadequate or is not suitable for its user;
- Lack of knowledge and experience on how to set up an adjustable workstation properly according to the worker's needs (considering both body build and job tasks);
- Poor working habits that remain uncorrected;
- Unsuitable job design that requires a worker to sit uninterrupted for longer than an hour at a time; and
- Lack of proper training, resulting in a lack of awareness.
Holding the upper body still allows the upper limbs to engage in such fine hand movements used in typing and operating a mouse (categorized as dynamic load). These are common examples of repetitious and monotonous movements. Repeated hundreds or thousand of times, hour after hour, day after day, year after year, these movements strain and gradually cause "wear and tear" on the muscles and tendons in the forearms, wrists and fingers. People who do repetitive work with their bodies in fixed and static positions are even more susceptible to getting RMIs.
Discomfort, numbness and tingling are the danger signs. If these signals are ignored, pain, chronic problems and long-term disability are likely to follow. More information on the interaction between the movements made by neck, shoulders and hands is in our OSH Answers web document on Repetitive motion injuries (RMIs).
Like repetitive and unvarying movements, a high work pace is quite a common reality in the most offices, even if it happens only occasionally. Regardless, whether it is arises from periodic overload or from uneven distribution of work, a regular high speed of work contributes to the development of MSIs very strongly.
The pace of work determines how much time working muscles have for rest and recovery between movements. The faster the pace, the shorter and less productive the recovery times become. This, in turn, increases the risk for RMIs.
A person may be able to set his or her work pace and adapt to the stresses that result. However, more harmful to one's health are external factors that increase the work pace and which are beyond the person's control, such as :
- having tight or frequently changing deadlines;
- knowing your performance is being monitored by some electronic system; or
- being overloaded with work.
The result is that the worker is denied any control over the timing and the speed of work, creating the feeling of "always being in a hurry." This haste and resulting stress while working cause the body muscles to tense up which, in turns, significantly accelerates the risk for developing RMIs.
Taken from http://www.oshforeveryone.org/wsib/external/www.ccohs.ca/oshanswers/ergonomics/office/risk_factors.html
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