| Physical work capacity refers to the maximum capabilities of the physiological system to produce energy for muscular work. Physical work capacity plays a central role in the process of carrying out ergonomic stress analysis in industry where a balance between job stress requirements and physical work capacity is maintained. If physical work capacity is exceeded, the worker is at risk of overexertion and may be producing lower quality work. If the job stress requirements are less than Physical work capacity, the worker may be underutilized and this could be an opportunity for productivity gains. Over the last four decades, ergonomics researchers and practitioners have devoted considerable resources to solving the problems associated with handling materials manually. Researchers have also agreed that since manual lifting is physically the most stressful material handling activity, it is best to contain the manual lifting injury hazard. Results of such efforts are reflected in terms of various guidelines and weight limit recommendations for manual lifting activities (e.g. NIOSH and the revised NIOSH). However, the cost, number, and severity of injuries had either continued to rise or remain unchanged because of the way the problem has been historically approached. Most industrial manual material handling tasks involve more than one type of activity (lifting, turning, carrying, etc.). And yet, most efforts have been directed at only one activity, little attention has been paid to designing/analyzing tasks that include multiple and diverse manual handling activities. By relating the energy expended in a job to the aerobic power of the individuals for endurance effort, an objective assessment can be made of the work capacity of the worker performing these activities without undue fatigue. Based on the assumption that a job can be divided into sub-tasks, and the average metabolic energy expenditure rate of the job can be predicted by knowing the energy expenditure of the simple tasks and the time duration of the job), the energy requirement to perform a certain task can be determined by summing the time weighted energy cost of all task elements over the time duration that task is being performed.;This research utilizes most suitable model(s) that could be used in determining human capabilities of performing multiple jobs. It also utilizes the physiological approach in determining human capacity for multiple jobs, and examines the combinations of lifting, carrying, and lowering activities, to develop an evaluation and a decision making tool that help designers, engineers, and managers overcome human limitations in all stages of design of product and process. Another contribution of this study is the development of general models that could be used in determining the maximum energy expenditure of individuals of certain age height, weight and gender within a targeted percentile. As a contribution to the area of physiological assessment of work, this study provides designers and practitioners, especially in the field of cellular manufacturing environment where high volume is dealt with, with a simple tool that could be used during both early stages of the design and during production stages to evaluate the physiological requirements of work and the capacity of people needed to perform them. The tool helps in labor assignment, determining work/rest periods needed to overcome peoples' fatigue besides the usual breaks assigned during the work shift. Despite its great advantages, there are some limitations that could be addressed in depth to further enhance the tool for better performance. |
