Many people get hurt at work and many people don’t get hurt, apparently doing the same job. Some people get hurt more often than others and some jobs hurt more people than others. The problem is further complicated by the fact that some people get hurt a lot and some people only a little and “doing the same job” doesn’t necessarily mean that the job is done the same way.
In the case of work-related musculoskeletal disorders (MSDs) the external forces and human behaviors that are known to cause damage are similar in many respects to those forces and behaviors that make us physically fit and healthy. So we have a fuzzy mess that opens the doors to analysts and politicians with different perspectives and who rely on their own interpretation of the statistics. These statistics only give us information about groups of people and types of jobs; it’s left up to the individual ergonomist to deal with particular people and particular jobs. Fortunately there are some trends that the statistics provide for us that we can use to develop simple laws for work design:
1. First, it is important to recognize that some features of jobs are the way they are for reasons other than managing the physical health of the worker. Plants in fields grow at ground level not at elbow level, truck tires are big and heavy, lots of people want to buy lots of chicken filets, and computers are a very useful aid to managing the business. In these cases it is up to the ergonomist to change what can be changed within the constraints imposed by these over-riding job features. The sometimes- conflicting constraints include: actually doing the job, productivity, safety and job satisfaction.
2. Second, it is important to recognize that increasing moments, caused by heavy weights and awkward postures, are more likely to cause acute injury, just like faster driving causes more serious accidents. Wherever feasible we should use engineering interventions to replace or assist human effort. There will never be a magic number, either for speed limits or for moments, and “feasible” is also a fuzzy word.
3. Third, we have the challenge of time
This article originally appeared in The Ergonomics Report™ on 2004-08-14.