Application of the NIOSH Lifting Equation in Assessing Risk of Musculoskeletal Disorders - Essay Example

Running Head: APPLICATION OF THE NIOSH LIFTING EQUATION IN ASSESSING RISK OF MUSCULOSKELETAL DISORDERS Application of the NIOSH Lifting Equation in Assessing Risk of Musculoskeletal Disorders [Name of Writer] [Name of Institution] Abstract The acronym MSD refers to the phrase Musculoskeletal Disorders. Under these disorders the most significant are Low Back Pain and other skeletal disorders. This paper intends evaluate a techniques referred to as the Lifting Equation, provided by National Institute for Occupational Safety and Health, for the avoidance of such MSDs. The NIOSH lifting equation was first provided in 1985 and later revised in 1985 which expanded its area of application in the field of biomechanical analysis. However, as with all other biomechanical assessment techniques, the NIOSH's lifting equation also was provided with its assumptions and limitations. However, in spite of these limitations the revised equation has played crucial role in the circumvention of work place related musculoskeletal and other related disorders. Application of the NIOSH Lifting Equation in Assessing Risk of Musculoskeletal Disorders Introduction In the year 1985 a temporary committee was organized by National Institute for Occupational Safety and Health NIOSH who along with NIOSH WPG reviewed the current literature on manual lifting. As a result this committee recommended the standard limits of weight lifting for healthy workers and also revised the lifting equation that was produced by NIOSH in 1981. Consequently, NIOSH evolved detailed explanations of the equation and played significant part in the analysis of methods and results of the lifting equation. (Townley et al., 2006) MSD stands for Musculoskeletal Disorders. These disorders include the wide ranging injuries and disorders that are work related and of these LBP are becoming one the most alarming issues. Currently, low back pain (LBP) and musculoskeletal disorders (MSDs) are the most distressing issues associated to the occupational safety and health issues. Even thought considerable measures have been taken along with job and worker related programs, then too these issues constitute for a significant percentage of economic cost and human suffering. The report entitled Back Injuries from the Department of Labor's Bureau of Labor Statistics has provided detailed discussion on the problem discussed above. [DOL (BLS)]Bulletin 2144, 1982. As per the findings of the DOL Report back disorders constituted for about 20% of all of the illnesses and injuries in the work place and about 25% of annual workers compensations. In addition to the above, according to a report by National Safety Council in 1990, it was expressed that, constituting for 31% for overall injuries, overexertion was the most widespread cause of work-related disorders. And due to these, back was the part of the body which was most prone to injuries and most costly to labor's damages systems. (Waters et. al, 1994) The Equation, its determinants and functions There are two key aspects of the RNLE the lifting index (LI) and the recommended weight limit (RWL). The principle result of the revised NIOSH lifting equation is the RWL. The RWL is limited in its scope to a particular set of circumstances of the task, as the load that could be endured for a substantial period of time for instance for eight hours by almost all of the healthy workers but without any emergence of the hazards of the low back pain (LBP). Here the healthy workers are referred to as the ones who are not suffering with any sorts of adverse health conditions that would welcome further hazards of musculoskeletal disorders. To begin with a standard load that can be safe for a particular lift and the reduction of the load when it become more stressful to endure the load an further i.e. the factors associated to the task become more and more unfavorable is the main notion behind the revised NIOSH (Thomas, 2002). The most accurate formulae for the reviewed version of the lifting equation for the calculation of the RWL is dependent on the productive model represents a weighting (multiplier) with six different variables, these are as follows; 1- Excellence of the hand to object holding represented as (C) 2- The space between the worker and the load horizontally represented as (H) 3- Frequency and the time period of the lift (F) 4- The height of the object from ground while lift (V) 5- Asymmetry angle (A) 6- perpendicular disarticulation during the raise of the object (D) (Faville et al., 2006) As already discussed that according to the revised lifting equation, the calculation for the Recommended Weight Limit (RWL) is based on a productive model comprising of six variable tasks, the weightings are articulated as coefficients that provide to reduce the weight that is constant, which characterizes the highest suggested load weight to be picked up under idyllic conditions. The following equation defines the RWL multiplicative model: Where HM, VM, DM, AM, FM, CM are the six variables discussed above with the multiplier M that represents the reduction coefficients in the equation, and LC is the constant load that is being lifted. LI is the secondary key product of the RNLE. The variable LI is the measure of the comparative intensity of the physical stress that is related to a standard lifting task manually. This measure of the physical stress is the product of the standard weight limit and the actually weight of the load that is being lifted. The following relationship defines LI: Where the Load Weight (L) = Weight of the object that is being lifted (lbs or kg). (Nyar, 2006) Moreover the LI was developed in order to estimate the requirement of physical power that was required for a particular single task of lifting manually. Here the 'single task' is referred to as the task in which the variables discussed above do not change significantly between number of lifts or obviously when only a single lift is under consideration. For the assessment of the multi task lifting jobs that were describes as the jobs in which there are noteworthy variations in lifting tasks that are done concomitantly, the producers of the RNLE also presented a modus operandi for the calculation of the composite lifting index (CLI), these were the jobs where the perpendicular distance from the ground (V) of the changes between number of lifts, for instance the palletizing job. It should be noticed that the lifting equation provided by NIOSH is the only comprehensive step taken in order to avoid occupational disability and pain, however, other than lifting there are other aspects too that can cause work-related MSDs these are, for instance, prolonged sitting, static postures, body vibration and direct trauma to back. Limitations of the Equation The NIOSH lifting equation has been provided in order to estimate the physical demand that is required for a particular manual lifting job with two hands. Like other tools for the assessment of physical needs, the application of the equation also has some limitations. These are discussed as follows: 1. The underlying assumption of the equation states that, manual handling tasks other than lifting are not of considerable significance as they require minimal energy, particularly in the cases of repetitive lifting tasks. These tasks can be climbing, walking, carrying, pulling, holding and pushing etc. moreover it is assumed that if such non-lifting elements of a particular manual job exceed more than 10% of the entire activity, then for the assessment of metabolic demand of these various tasks heart rate or energy expenditures maybe required (Garg et al. 1989). 2. In addition to the above the equation doesn't accounts for the unexpected or unpredicted conditions or results which workplaces are highly prone to, these can be falls, slips or heavy loads. In such cases additional biomechanical psychoanalysis is essential for the assessment of physical demands for such traumatic occurrences. Moreover the effects of climatic variations such as temperature and humidity are also crucial for their effects on energy utilization and heart beat. 3. Moreover, the lifting equation doesn't applies to the assessment of tasks that involves lifting while being seated, or kneeled or lifting with one hand or lifting in a limited work area, and also for the lifting of the objects that are unstable. The term unstable here refers to the objects whose center of mass changes during the lifting activity, examples of such objects can be partially filled bags or liquid containers. Moreover, the equation is also not meant for high speed lifting, shoveling or lifting of wheelbarrow. For all of the varied tasks indicated above, task specific biomechanics are crucial for the estimation physical demand of lifting. 4. It is important to know that friction or coupling between the foot of the lifter and floor plays an important role in a successful manual lift of an object. This coupling between foot and floor is represented by the coefficient of friction. Under the revised lifting equation, this friction coefficient is assumed to be from 0.4 to 0.5, which normally the level of friction between a leather sole of a nonslip-type work shoes and clean, dry and ungreased floor. If these conditions vary so as to alter this friction coefficient considerably, then the application of the revised lifting equation may not be appropriate. 5. Another considerable assumption taken by the developers of the revised lifting equation is this that the risk associated to low back injuries while the lifting and the lowering of the same object are analogous. Which means that if a box if lifted up to a certain high and then it is lowered down to the floor the hazard associated to the MSDs is equal. However, this assumption may not be valid in a case when the box is actually dropped down rather than being lowered down all the way to the ground. (Waters et al., 1994) Alternative approaches There are other approaches too for the assessment of physical needs and for the attainment of the primary objective i.e. the avoidance of MSDs. Some of these are as follows: a) Biomechanical Model Under this methodology the effect of various stresses on body during the work tasks and the mechanics of muscular activity are being considered (Anderson & Chaffin, 1986). By the help of these methods the cumulative and acute loads at the key body joints can be calculated specifically loads at the lumbar spine ((Keyserling et al., 1980). Moreover, the risk associated to high demand tasks such as carrying, holding, lowering, pulling, pushing and also lowering and lifting can also be estimated by the help of biomechanical models. These methods assume the rational concept that the more the force exerted, the more will be the risk of MSDs. Following aspects are being considered by biomechanical approaches: i. Load-magnitude and bearing of force exerted on each hand; ii. Physical features of the laborer, including sex, height, power; iii. Posture-positioning of the main body joints. b) Psychophysical Methods The human reactions to particular tasks are being considered under the psychophysical methods. The major advancements in the approach were pioneered by Snook and Ciriello. The notion on which the psychophysical technique is based on is the far-reaching technical analyses of manual objects handling jobs to establish secure lifting loads. The main methodology begins with the advancement that test subjects are being provided with specified loads or weights which they are asked to carry for a certain duration of time, and then it is identified that what was the time period for which the for which these subjects lifted their respective loads without being getting weak, tired or got out of breath. Then these data are being collected on tables of maximum acceptable weight of load (MAWL) for men and women for carrying, lifting, pulling, lowering and pushing. These tables are being named after their creator Snook as they are called the Snook tables which represent the levels of maximum endurable weights. Further, these information from the 'Snook tables' are being divided into proportional values for example 10%, 20% or 90% of the overall theoretical workplace population. (Townley et al., 2005) Conclusion It was in the year 1981 when the first lifting equation for manual lifting tasks was developed by the National Institute for Occupational Safety and Health (NIOSH) for the estimation of the physical require for manual lifting tasks. However it was revised by an ad hoc committee arranged by NIOSH in 1985. The new equation that was presented in 1985, played significant role in the avoidance of LBP and MSDs and other occupational injuries as it was first time when formal documentation of the equation was being provided along with the procedures that could be used to analyze and interpret the results of revised lifting equation. The reason for the development of the lifting equation was to avoid the disastrous occurrences in the forms of MSDs, LBP, other work related injuries and disorders along with severe human sufferings, as these issues constituted to a prominent proportion of the overall work related disorder and illnesses thus heavily contributed for mounting worker's compensation expenditures. Even though the equation has improved the probability of such issues, there are some limitations that exist in the application of the revised lifting equation. These limitations significantly limit the scope of the equation, as it assumes that lowering and lifting in unfavorable environment and climatic conditions are inappropriate. Moreover the underlying assumptions limits the scope of manual lifting tasks only to the ones that are being executed with both hand and the durations doesn't exceeds eight hour, moreover the lifting tasks that are being performed while being seated in a limited area also doesn't fall in the scope of the equation. In addition to the above lifting of unstable objects or high speed lifting also aren't being dealt with by the revised lifting equation. Not only this lifting tasks whose elements vary considerably i.e. jobs where an employee may executes a succession of lifts at a particular workspace for a set interlude of time (either multi task or a single task), and then moves or revolves to a different terminal or job part to carry out a dissimilar sequence of elating tasks (either multi task or single task). Such kinds of job and others that are quite similar are referred to as the sequential lifting jobs and therefore another methodology is required for the calculation of the comparative physical power of such kinds of physical lifting tasks than the ones that were intended in the NIOSH lifting equation. References Andersson, G. & Chaffin, D. (1986) 'A Biomechanical Evaluation of Five Lifting Techniques', Applied Ergonomics, Vol.17: 2-8 Faville, B., & Shulenberger, C., (2004) 'Applying Manual Material-Handling Guidelines to jobs Tasks' Occupational Hazards, Vol. 66(11): 35-38 Garg, A. (1989) 'An Evaluation of the NIOSH guidelines for manual Lifting with Special Reference to Horizontal Distance', American Industrial Hygiene Association Journal, Vol. 50: 157-164 Keyserling, W.M., et al. (1980) 'Establishing an Industrial Strength Testing Program.' AlHA Journal, Vol. 41: 730-736. Nayar, N. (2006) 'Workplace Ergonomics and Simulation', Assembly Automation, Vol. 30(16): 25-28 Thomas, R. (2002) Musculoskeletal Disorders in Health-Related Occupations, IOS Press pp.171-180 Townley, A. C., Hair, D. M., & Strong, D. (2006) 'Quantifying Lifting Hazards', Professional Safety, Vol. 50(5): 5-30 Waters, T. R., Anderson, V. P., & Garg, A. (1994). 'Applications Manual for the Revised NIOSH Lifting Equation', US Department of Health and Human Services Read More