Abstract
Ergonomics is a field of applied science that focuses on arranging and designing equipment used by people in a manner that will result in optimized efficiency and safety. The emergence of humanistic management theories has created an emphasis on developing work environments that recognize employee values and needs. One such aspect of these theories is the concept of ergonomics, which recognizes the need for a safe work environment in achieving efficiency and organizational goals. The environment studied in this simulation is a simple workshop that has a computer desk, server, conveyor belt, office chair and two computer monitors. The selected employee for this study is a female with a height of 170 cm, weight of 68 kg, and a waist to hip ratio of 0.74; additionally, a male, height 179 cm, weight 95 kg, and waist to hip ratio of 0.87. The task involves lifting a cylinder of 12 kg to a tray of height 105 cm. The female proceeds to sit at the computer desk, then the male walks to the server where he reaches for this equipment's monitor. Both employees have a foot placement zone of 50 cm.
Introduction
According to Mirakhorlo and Azghani (2015), lifting is a major causation for work-related musculoskeletal injuries (MSKD). The authors further highlight that manual material handling, such as the cylinder used in this experiment, predisposes an individual to Low Back Pain (LBP), Low Back Disorder, and other MSKDs. One essential ergonometric issue in lifting is the technique used to perform the task. For example, one individual may opt to squat to lift a heavy object, whereas another may simply bend to perform the same task. Ideally, both individuals end up lifting the object, but the level of exposure to injury is different. Amazeen, Tseng, Valdez and Vera further stipulate the perceived heaviness when lifting an object is significantly influenced by the technique used. These authors argue that this perception stimulates the muscles and joints to exert the perceived amount of force or movement to lift the object. Therefore, when an object is perceived as being heavy, the body exerts a considerable amount of energy in preparation to achieve this task. Additionally, some lifting may require more than a single movement, for example, lifting an object from the ground to place it on a high surface. Such a scenario involves a lifting technique, a posture to hold the lifted material in the air as the body aligns with the high surface, and a placing style that does not drop the object nor strain the muscles or joints. A combination of these techniques and their study is part of what is encompassed in the scientific discipline of anthropometry. Generally, anthropometry considers the human body similar to a machine comprising of several levers; consequently, for optimum functioning of these levels, specific proportions and measurements have to be identified for each operation.
Methodology
Previously, studying the ergonomics of the work environment proposed in the introduction section would require having a physical place with the individuals and equipment mentioned. However, similar to other current studies, this research will rely on digital human modeling software to analyze the ergonomic implications of the activities in the proposed work environment. A major advantage of digital human modeling is that it allows managers and occupational safety specialists to adopt a proactive approach in evaluating job designs and the feasibility of each operation in regards to injury. The use of this simulation software allowed the researcher to evaluate several scenarios using the two sample employees without any real person being exposed to injury or fatigue. The anthropometrical data used in this study was generated based on the average size of a male and female adult as per the software's database. The simulation platform used is Jack Siemens version 8.0.1. The equipment utilized in this study are a cylinder, which is hypothesized to be holding a gel weighing 15 kg. The employees have to place the get on the tray, as placing in on the floor causes it to react. The tray is designed to optimize ergonomics by having a removable surface so that employees can lift the cylinder through its frame and then slide the bottom under the lifted object. As previously stated, the height of this tray is 105 cm, the female employee 170 cm, and the male one 179 cm.
Figure 1: Screenshot of the Work Environment
Results
Figure 2: Squat Graph
Figure 3: Stoop Graph
Figure 4: Semi Squat Graph
The three graphs above indicate that there is more muscle synergy when the lifting is done by squatting. Stopping is identified as the least ineffective mode of lifting, which further means that it predisposes employees to MSKDs. The semi squat has high frequencies, but the fact that only some of the muscles reach these heights indicates it is not optimal for lifting the 15kg load over a 105 cm height.
The data provided in table 1 and 2 above was derived based on the scenario where the female employee lifted her load through the squatting technique, whereas the male employee opted to stoop. Based on the data in these tables, it is evident that the employee that stooped used more energy for the lifting, 402.5 kcals as compared to the squats 288.1 kcals. This finding further highlights that not only is squatting a less injurious method of lifting in comparison to squatting, it also consumes less energy and thus an employee will not tire quickly. Nonetheless, in both techniques there is a nominal risk of muscle injury as the total energy expenditure is below the standard 8.245 kcal/min.
Figure 5: Female employee squatting
Discussion
This discussion section is based on data collected from secondary sources and the simulation results. Landry (2003, p.1) argues that the perception of risk of exposure to a health concern significantly affects the steps an individual takes to protect themselves against the specific issue. Landry further highlights that the traditional perception that women’s jobs are less menial has reduced research interest in their exposure to occupational injuries. In a research by Nordander et al.(2007, p.939), which occurred after Landry’s argument, established that MSDs are more common among women than their male counterparts are. In particular, Nordander et al. (2007) found that neck and upper body related MSDs were prevalent among the female working population. Awkward postures among women workers increased their risk of suffering from MSDs.
Perhaps as intent to highlight the risk that females face from MSDs, Nordabder et al. (2007) established that women register higher muscular activity at work. Additionally, these researchers highlight that women workers have less time for recovery from occupational, physical stresses because their after-work time is considerably spent performing household tasks.
According to the Finnish Centre for Pensions (2012), among residents aged between 16 and 64 years, an estimated 7% were given a disability pension: approximately 33% of these recipients suffered from MSDs. Prolonged standing, exposure to vibrations and awkward postures are some common causative factors of MSDs among workers. Examples of MSDs resulting from these elements include diffuse arm pain, tenosynovitis, and osteoarthritis. Madan and Grime (2015) propose job rotation, utilization of mechanical aids and elimination of some tasks as solutions to MSDs in the work environment. During the diagnosis of these conditions, it is critical that the medical practitioner establishes the cause of the illness; this is beneficial in reducing job-related MSDs in future at the patient’s workplace. Poorly designed work environments do not cause all MSDs; nevertheless, these surroundings may aggravate an employee’s condition.
Recommendations
The findings from the simulation indicate that women can achieve better ergonomics at work if they are trained on proper lifting techniques. Consequently, the secondary data highlighting a higher risk of work-related injury among women than men is representative of reduced awareness among this demographic. One important element of creating an ergonomics strategy is to understand the individual attributes of each employee and the nature of the task they perform. For example, the male employee in the study was required to lift the cylinder and then operate the conveyor belt, which are two activities predisposing him to lower back injuries. On the other hand, the female employee had to use the keyboard, which predisposed them to wrist injuries. Consequently, formulating an ergonomics strategy would require a uniquely tailored plan for each of these roles to mitigate their possible work-related injuries.
References
Amazeen, E. L., Tseng, P. H., Valdez, A. B., & Vera, D. (2011). Perceived Heaviness Is Influenced by the Style of Lifting. Ecological Psychology, 23(1), 1-18
Landry, L.G. 2003, Women's perception of risk from occupational musculoskeletal exposures, University of California, San Francisco.
Madan, I. & Grime, P. 2015. ‘The management of musculoskeletal disorders in the workplace’. Best Practice & Research Clinical Rheumatology, pp. 1-11
Mirakhorlo, M., & Mahmood Reza, a. (2015). Similarity of different lifting techniques in trunk muscular synergies. Acta Of Bioengineering & Biomechanics,17(4), 21-29.
Nordander, C., Ohlsson, K., Balogh, I., Hansson, G., Axmon, A., Persson, R. & Skerfving, S. 2008. ‘Gender differences in workers with identical repetitive industrial tasks: exposure and musculoskeletal disorders.’ International archives of occupational and environmental health, vol. 81, no. 8, pp. 939-47.
