Workplace Injuries and Human Factors
The discipline of Human Factors may be thought of as a "bridge" between the life sciences (Physiology, Psychology, Biomechanics, Sociology) and Engineering. The goal to Human Factors is to engineer everything in our environment to match the capabilities and limitations of human beings. When this is accomplished in the workplace, the result is improved safety and efficiency.
The applications of Human Factors in industry are varied. Often, these applications are divided into two general categories: cognitive and physical. Cognitive Human Factors concerns our abilities to perceive, process, and react to information. Perhaps the best-known examples in the area of forensic engineering are in the areas of Accident Reconstruction, Failure Analysis and workplace injuries under the Occupational Health and Safety Act. Other examples are the interaction of humans with computers and workplace design.
The physical side of Human Factors concerns how humans move or apply force to objects in the environment. The remainder of this article will explore these kinds of applications and their relationship with certain kinds of injuries.
The musculoskeletal system consists of the muscular, skeletal, nervous, and circulatory systems that are involved in movement of the limbs. Musculoskeletal Injuries, or MSI, are those injuries caused by internal forces that act of different parts of the body either in moving objects or in simply moving the limbs.
MSI's may be subdivided into two general categories: lower back injuries and Repetitive Strain Injuries or RSI.
Lower Back Injuries
The lower back is highly susceptible to injury. In fact, the large majority of people will, at some time in their lives, suffer from some form of lower back pain. Typically, we see examples of lower back injuries in the more labour intensive workplaces, in tasks where individuals are required to lift heavy loads, where awkward postures are required due to workplace layout or confined spaces, or where repeated or sustained bending is required. Construction, meat packing, and warehousing are all industrial activities particularly prone to lower back injuries.
Many of these injuries concern the intervertebral discs, particularly the disc in the extreme lower back known as the L5/S1 disc. To understand how these injuries occur and how Human Factors may be applied to assess and prevent these injuries, we must first understand a little of the structure of the back and how it supports loads.
The spine is basically comprised of bones, or vertebrae, and discs, which connect the vertebrae, absorb shock, and provide some degree of mobility to the spine. The discs may be thought of as being like flexible jelly donuts filled with a thick gel or nucleus.
Injuries to the back include microtears (small injuries which weaken the wall of the discs, causing them to change the size or shape and making them more vulnerable to further injury,)bulging of the disc (often called a "slipped" disc,) to total rapture of the disc, where the disc wall actually breaks and the nucleus escapes.
By using computer programs that model the mechanics of body posture and loading Human Factors specialists can estimate the compression forces generated for a specific posture. All that is required is video footage, taken from the side of the subject, with all of the locations of the major body joints shown by markers worn by the subject. While there are limitations to these computer programs, such as an inability to model the effects of twisting motions, they allow us to determine generally whether a lifting task is associated with an unacceptable level of risk.
Once the assessment is complete, if the Human Factors specialist determines that the task carries an unacceptable degree of risk, recommendations can be made to either make engineering modifications to the workplace, or modify the procedures used.
Repetitive Strain Injuries (R.S.I.)
The term Repetitive Strain Injury covers a range of injuries, all of which involve an accumulation of smaller injuries that create what can be a crippling condition. Four basic factors interact to cause RSI.
One of these environments where RSI is highly prevalent is on assembly lines, where workers are performing the same set of motions hundreds or thousands of times a day. As assembly line rates have increased and the job of each assembly line worker has been simplified into fewer and fewer motions repeated at higher and higher rates, RSI's have become an increasing problem.
Some common RSI's are Tendinitis, Tenosynovitis, and Carpal Tunnel Syndrome.
To assess a task where there is a known problem with RSI, a Human Factors Specialist will scrutinize the task in great detail, closely examining the motions and measuring the forces and cycle times, to determine to what extent the four factors mentioned above may contribute to the injury problem.
Walters Consulting Corporation has developed considerable experience in Human Factors with projects that have been performed in Accident Reconstruction and Failure Analysis. We are now able to offer an expanded expertise to our clients with an accurate assessment of workplace related injuries and methods for improving safety and efficiency.
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