NOIRS 1997 Abstracts of the National Occupational Injury Research Symposium 1997. Washington, DC: National Institute for Occupational Safety and Health, 1997 Oct; :17
A majority of fatal and non-fatal accidents at the workplace occur due to fall-related incidents, particularly in the construction industry with twice the rate of nonfatal falls as the average industry. Most falls result from momentary loss of postural stability of the worker. Working on elevated and/or inclined surface can produce excessive demand on the postural control system of the worker. For example, ironworkers and roofers traditionally work at raised and/or inclined surfaces and account for 70% of fall-related fatalities. A laboratory-based study was performed to investigate the effect of surface elevation, surface inclination, environmental lighting and noise on postural stability of workers performing simulated tasks. Twenty young (age =3D 25.0 =F1 2.2 years) and twenty old (age =3D 53.7 =F1 3.2 years) industrial workers, with equal number of males and females in each group, participated in the study. The subjects performed three kinds of tasks of Stationary, Bending, and Reach. The subjects performed these tasks on specially constructed surfaces with combinations of three levels of elevation (0, 30.5, and 61 cm high), and three levels of inclination (0, 14, and 26 degrees). The environmental lighting was varied between poor ( < 0.2 footcandles) and good ( > 40 footcandles). The subjects were fitted with lightweight wireless headphones that presented audible distraction in the form of pre-recorded construction sound at a setting sufficiently loud to interfere with levels of normal human conversation. The forces and moments exerted by the subjects were recorded using a piezo-resistive force platform and the data was analyzed to yield the movement of the center of pressure (CP) as a quantitative measure of postural sway. Stepwise regression analysis was used for identifying the significant interactions. Dependent variables included the measures of sway area and sway length, with the age, height/weight ratio, and gender included as covariates. Mixed model analysis showed highly significant fixed factor effects for elevation (p < 0.001) and environmental lighting (p < 0.001) for all three tasks for both sway area and length, with increasing sway area and length for increasing elevation and inclination The sway length increased significantly with increasing inclination for the Bending and Stationary tasks, but was non-significant for the Reach task. Sway area increased significantly (p < 0.05) with increasing inclination for all three tasks. The results are indicative of postural balance performance that deteriorates with increase in elevation of the working surface as well as the inclination of the surface. This introduces additional burden and may be a major contributor to momentary loss of balance resulting in falls. Environmental lighting was also found to be a significant risk factor and introduced further burden on the postural stability of the worker. The experiment was performed under laboratory conditions, with no workload and on firm support surface with sufficient coefficient of friction. These risk factors may further jeopardize the postural stability of the worker at an elevated and/or inclined surface. Results from this study would be helpful in identification of specific risk factors and their relative contribution in postural imbalancement during dynamic task performance on inclined and/or elevated surfaces.