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Biomechanics has been around for many years and has been used to describe many different disciplines. For our purposes, the word biomechanics can be described as the scientific method concerned with the musculoskeletal system and component issues and their relationship with mechanical behavior when physical work is performed. Some universities consider biomechanics as part of a bioengineering, biomedicine or biomedical course of study. All of these terms have a small degree of relativity but each discipline is vastly different. Fundamentals of biomechanics may be necessary for these curriculum courses of study, a more in depth curriculum in biomechanics are necessary when studying occupational biomechanics. The need in today’s society to apply biomechanics to improve working conditions is highly regarded both federal agencies (OSHA and NHSTA) address the issue for workers and commercial fleets. This need involves the analysis for reducing injuries and death and their associated costs. Figures have been thrown around as to percentages and numbers of injured and death on the job, but this is a subject for epidemiologists and not the study of the principles of biomechanics. An injury-scaling method known as Abbreviated Injury Severity (AIS) is believed to quantify injuries, but this scale relates to probability of death and not the single injury itself. Examining figures is a method of surveillance to see if the injuries and death rates are heading in the right direction. Biomechanics uses the laws of physics and engineering concepts to describe motion of various body segments and their related forces during occupational functions. A simple slip and fall can cause serious injury or death because the impact with the floor or an object is over a short period of time (milliseconds) and usually involves a localized segment of the body. Force is a product of mass multiplied by acceleration, and acceleration is a product of the change of velocity divided by the change of time. With this description, it is easily understood that force greatly increases with the decrease in time over which the force is applied. If the force is sudden, injuries such as contusions, fractures, concussions, etc., can occur. For activities involving overexertion with or without repetitive motion, injuries such as tendonitis, cumulative trauma and nerve disorder, lower back disorders, etc., can occur. Understanding the forces and dynamics to help prevent these injuries is the cornerstone of occupational biomechanics. In the late 1800s there was little concern for minimizing human injury in the workplace because labor was plentiful and economics was the driving force, while occupational biomechanics was not understood. Over the years, much has been learned about occupational biomechanics and its importance. The general consensus divides six different biomechanical methodological areas. These occupational biomechanical areas include modeling methods, anthropomorphics, mechanical work capacity, bioinstrumentation, motion and time-evaluation and kenesiology. Each of these methods is used to monitor, evaluate and determine corrective actions and causes relating to injuries and death in the workplace. Kenesiology is the study of human movement without considering the actions of force. Variables in kenesiology are angular and linear movement, velocity, acceleration, as well as internal and external forces and movement. Kenesiology is an important discipline in understanding biomechanics and biomechanical applications. The challenge in understanding biomechanical modeling is that a true understanding of the human body kinematics is necessary and must be applied appropriately. Kinematics, which involves unrelated experiments, would yield little or no useful data when applying this data to a specific segment. Anthropometrics is the study of human body segment measurements of various populations, localized and globally. It is said that to design a machine for the average person is to design a machine for no one because the average person truly does not exist. Machine and automotive designers shoot for the 95th percentile values when researching product liability issues and safety. When analyzing anthropomorphic data, caution should be exercised when the source of this data is not known or not understood. In earlier times, the only available anthropomorphic data came from the military, which gathered data from robust healthy males and females within a certain age group. The same skewing of data would occur if one tried to determine the average size of a college student and included all the athletes. This type of information greatly limited the use, analysis and outcomes for ergonomics and biomechanics. Evaluating the capacity of a worker is the primary target of occupational biomechanics. Since various work capacity varies greatly the variables such as genetics, age, fitness, skill, as well as many other factors must be explored, categorized and evaluated as they relate to the position to be filled. Biomechanical modeling is one way of attempting to analyze the physical criteria needed for specific occupational positions. The modeling can be as simple as pros and cons written down or as complicated as a 3-D computer animation. Instrumentation is crucial to the collection and organization of the data necessary for evaluating occupational biomechanics. Force plates and transducers or accelerometers are compact tools used in an effort to obtain accurate and reliable kinematics measurements for meaningful study. After gathering as much data as possible, various charts, graphs and tables can be created for use by the occupational biomechanical team. These tables should classify motion and time so that analysis of the work capacity can be determined. It is said that biomechanics in general is a combination of engineering and medical science, but correctly stated it is a discipline of its own using specific areas of engineering and anatomical science. As stated earlier, the study of patterns and values is in the realm of the epidemiologists but can and does assist occupational biomechanics in its effort to place a legitimate science in the pursuit of reducing injuries and deaths and the related costs. Some of the statistics reported are as follows: In 1988 in the United States 12.4 percent of workers had musculoskeletal disorders. Approximately 52 percent of worker impairments are from the back and spine, while 11 percent are of the lower extremity or shoulders. These impairments are said to be divided equally between men and women. As expected, as the working force gets older, impairments increases. Musculoskeletal injuries in the United States in 1988 were approximately 32 million (133 per 1000 persons). The injuries were higher for males and females. More recently, in 1990 there were 1.1 million disabling work injuries in United States. Three types of mechanisms cause 72 percent of injuries in the work force: overexertion 32 percent, struck by objects 23 percent, and falling 17 percent. Total cost of musculoskeletal disorders in United States is estimated at $126 billion for 1988. Back problems are usually more prominent since much lifting; carrying and twisting are performed during an average workday. Another problem, which is on the increase with the advent of computer stations, is carpal tunnel syndrome (CTS). Carpal tunnel syndrome is the compression of the median nerve due to repetitive motion. The impairment is also exacerbated or compounded by specific types of work. According to a Swedish study, CTS was found to occur three times more in workers who perform intense work with their hands than in simple control type of work. Support for occupational biomechanics is gathering strength and is supported by social and legal communities. It is critical to choose the correct person for the task. It has been shown that persons who are not able to demonstrate an isometric strength test sufficient to perform certain assigned jobs had an injury rate and severity for musculoskeletal injuries three times greater than those who were stronger. Ergonomics is another discipline, which studies the relationship between the human body and the working environment. Ergonomics issues including sitting standing, reaching etc., all of which are studied and become part of an occupational biomechanics study. Occupational biomechanics is a discipline used by many researchers and companies. The discipline is also taught in many universities, either in conjunction with the public health degrees or OSHA-related degrees. The following are some categories of interested groups in occupational biomechanics: Industrial and production engineers; Industrial hygienist occupational physician or nurse; Orthopedic or rehabilitation physicians including physical therapists; Ergonomics and biomechanics personnel Safety managers and labor relations personnel; A company may decide to expand or redesign its workplace and would be in need of an occupational biomechanics study relating to machines, tools, workstation benches, etc. A company may also feel that their injury rate is intolerable and require an occupational biomechanics study with suggested improvements. Only biomechanics can determine a range or tolerance threshold of occupational injuries. Medical training is to determine a diagnosis and provide treatment. Biomechanics is not considered a medical function but the occupational biomechanical person must be trained in anatomy and injury mechanisms. DENNIS R. ANDREWS is principal of Accident & Safety Consultants.

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