Revised Force-Endurance Models for the US Workforce

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Project Summary Obesity is a risk factor for workplace injury, and its growing prevalence may be associated with increases in the future incidence and cost of injuries. Although the health consequences of obesity have gained increasing attention, there are still major limitations in what is known regarding the effects of obesity level on work capacity and injury risk. This project will assess obesity-related differences in endurance and fatigue, which will provide useful information for understanding the impact of overweight and obesity on the performance of occupational activities and the subsequent risk of injury, particularly for those tasks requiring static postures that can be limited by fatigue development. In addition, the objective of this work is to provide ergonomics practitioners with revised force-endurance models that can be applied for work design and evaluation. Specific Aim 1 will address the main and interactive effects of obesity level and workload for sustained isometric hand grip, shoulder abduction, and torso extension tasks. Endurance will be evaluated at four levels of relative loading to provide results for an occupationally-relevant range of task demands. To achieve this aim, individuals who are non- obese, overweight, or obese and aged between 25-54 years will be recruited and asked to come in for four experimental sessions. During each session, participants will complete an endurance task for each muscle group at one workload level while endurance time and fatigue- related responses are quantified. With the data collected from Specific Aim 1, revised force- endurance models will be developed in Specific Aim 2. It is hypothesized that higher levels of obesity will be associated with impaired endurance capacity. It is also expected that the existing models are not predictive of endurance time for overweight and obese individuals, limiting their utility in ergonomics practice and requiring revised models to be protective of the muscle capacity of the changing workforce. Results from this research will contribute to understanding the impacts of obesity on the development of muscle fatigue, which is important for discerning the link between personal risk factors, such as obesity, and the risk of workplace injury. Application of the revised models can facilitate improved workplace design and job evaluation to accommodate the capacities of workers who are overweight or obese. Consistent with the National Occupational Research Agenda objectives, the long-term goal of the proposed work is to determine the impact of occupational exposures for the prevention of musculoskeletal disorders and the improvement of worker health.