Nicole Matoushek PT MPH CSHE CEES
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Back Injuries in the Workplace
Lower back injuries are among the most common complaints seen in primary care and workers’ compensation. Approximately 85% of the general population in the western world is afflicted with an episode of back pain in their lifetime (1). The peak incidence of lower back pain is found to be highest during the most productive years of life, ages 25-60, making work-related lower back injuries a major health concern (2). In order to address this health concern, a strategic plan to reduce work-related lower back injuries is required. The first step of this plan requires the identification of ergonomic risk factors that can contribute to injury.
The next step in reducing lower back injuries involves implementing ergonomic control measures. The third step in back injury prevention involves following safe work practices including utilizing proper posture and safe lifting techniques during work activities.
Ergonomic Risk Factors
Ergonomics is a multidisciplinary field, which addresses the interactions of people, work tasks and the total work environment. Ergonomic risk factors are job attributes or exposures that increase the probability of developing of a work-related injury. Ergonomic risk factors are not necessarily causal factors for injuries. Examples of ergonomic risk factors include: repetition, forceful exertion, stressful postures, contact stress, vibration and temperature extremes. The presence of an ergonomic risk factor does not necessarily mean that a person is at an excessive risk for developing a work-related injury. However, the greater the exposure to an ergonomic risk factor, or the exposure to multiple risk factors, generally results in the greater probability of developing a work-related injury. Therefore, reducing ergonomic risk factors in the workplace will decrease the probability of an individual developing a work-related injury.
Postural Risk Factors
The primary ergonomic risk factor responsible for back injuries in the workplace is stressful posture. Posture refers to the position of a specific anatomical body part in relation to an adjacent body part. Stressful postures occur when an extreme or awkward body position places undue stress on the muscles, ligaments and joint structures that are used to maintain the position. Stressful postures can result in physiological damage to the tissues within or around a joint. Stressful postures typically include end range of joint motion and excessive rotation. In order to reduce the physiological damage induced by poor postures, these stressful postures should be minimized. To effectively reduce postural stress, the evaluator must be familiar with the components of posture and how these components induce physiological damage. The components that define posture include: adjacent body parts, the angle of the joint connecting adjacent body parts and motion.
Adjacent body parts are the body parts above and below the segment that is being analyzed. If assessing back posture, the position of the legs, and the thoracic and cervical spine is critical. If the adjacent body parts are positioned in awkward angles in relation to the spinal segment, there will be a greater physiological stress placed on the tissues that support and maintain the position. The more awkward the position of these adjacent body parts is, the greater the physiological stress and potential for damage. To reduce the postural stress, adjacent body parts should be maintained in positions that promote open packed joint positions, tissue relaxation and maximize the circulation to the working tissues.
The angle of the joint connecting the two adjacent body segments will influence the degree of joint and tissue stress. Awkward joint angles place physiological stress on the joint structures, muscles and tendons surrounding the joint. The more awkward the angle of the joint is, the greater the tissue damage. Awkward joint angles, including end range of motion and excessive rotation should be minimized in order to reduce the physiological stresses.
The motion component of posture refers to whether the posture is static or dynamic. If the posture is static, there is no motion and the position must be held for a period of time. Static postures can cause tissue fatigue and microtrauma due to continual muscle firing and strain on the tendons and ligaments that are used to maintain a position. The amount of muscle recruitment and fatigue also increases with stressful postures. Dynamic posture, on the other hand, involves rotational forces of one body segment relative to another about a common axis or joint. Dynamic postures involve angular displacement, velocity and acceleration. Dynamic postures are preferred over static postures due to the ability to utilize multiple muscle groups, enhance circulation and prevent local tissue fatigue. Due to the physiological requirements to maintain muscle and tendon functions, no position can be maintained indefinitely. Hence, all positions have some dynamic component to them. The more stationary a position is however, the greater the degree of risk for tissue fatigue and injury. Therefore, dynamic postures and the ability to vary a position while working are of utmost importance when considering reducing work-related injuries.
Preventing Back Injuries with Ergonomic Controls
Using ergonomic controls can be an effective method to prevent lower back injuries in the workplace. Ergonomic controls are control methods that reduce the duration, frequency or the intensity of the ergonomic risk factor to the employee. There are three types of ergonomic control measures that can be used to prevent lower back injuries, they include: engineering controls, administrative controls and work practices.
Engineering Controls
Engineering controls are control methods that involve modifying the work interface. Examples of engineering controls include; modifying the work materials, workstation or the equipment and tools that are used. Engineering controls that improve back postures and reduce back strain are illustrated below:
•Adjust work surfaces to minimize awkward postures and ensure appropriate sitting and standing postures.
•Provide foot rests to standing and sitting workstations to improve back postures and reduce stress.
•Tilt work surfaces to bring the work closer to the worker.
•Make the work more accessible by raising or lowering the work to bring it closer to the worker. This can be achieved with lifts, platforms, or scaffolds.
•Reduce the size and weights of the materials that are handled.
•Design the workstation for the target population. If target population consists of females, the work area should be designed with the target population in mind.
•Provide carts to reduce material handling activities.
•Maintain all equipment on a regular basis.
•Install mechanical lifting aids, such as lifting devices, reaching devices and pulley systems to counterbalance loads.
•Provide joint protection, anti-vibration or shock absorbance to reduce exposure to physical environment (vibration, concrete floors, cold). This can include anti fatigue mats, gel insoles or anti-vibration seating systems.
Administrative Controls
Administrative controls involve modifying the work process, flow or organization to reduce the exposure of the worker to the ergonomic risk factor. Administrative controls that will reduce the likelihood of back injuries include:
•Provide job rotation, or alternating work activities.
•Reduce the length of work shifts.
•Limit employee overtime.
•Increase the number of employees available to perform a task.
•Implement mandatory or additional rest breaks.
•Alternate highly repetitive work tasks with less repetitive work tasks.
•Reduce production quotas or machine pace.
Work Practices
The third method of controlling work-related back injuries involves safe work practices. Safe work practices include general health habits, complying with safety rules and the practice of proper posture and good lifting techniques. The practicing of safe health and work practices can help minimize the occurrence of lower back injuries in the workplace.
Examples of safe work practices are given below.
•Maintain good health habits.
•Participate in a smoking cessation program.
•Participate in a weight loss program.
•Participate in a regular exercise program.
•Following safety rules.
•Understand the limitations of safety equipment.
Proper Posture
As illustrated above stressful postures can contribute to the development of lower back injuries in the workplace. Therefore, reducing stressful postures and maintaining proper back posture throughout the workday is important in order to reduce lower back injuries. Proper postures, are those postures that due to the position of the adjacent body parts, the connecting joint and the degree of motion, result in the least amount of physiological stress and fatigue on the local tissues. Proper postures place the least amount of stress and strain on the working ligaments, muscles and joints and result in less tissues damage. Proper postures should be maintained during both static and dynamic activities.
References:
1) Bigos S, Spengler D, Martin N, Zeh J, Fisher L, Nachemson A, Wang H: “Back Injuries in Industry: A Retrospective Study II. Injury Factors”. Spine vol 11, no 3, 1986.
2) National Bureau of Labor Statistics
3) ErgoRehab, Inc: [URL=http://www.ergorehabinc.com]www.ergorehabinc.com[/URL]
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Nicole Matoushek, PT, MPH, CSHE, CEES
http://www.ErgoRehabinc.com
http://www.ErgoRehabBlog.com
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