The Influence of an Inclined Surface on Flat Surface Postural Control

Abstract

An epidemiological study conducted by the NTOF surveillance system of the National Institute of Safety and Health (NIOSH), analyzed 15 years of data (1980–1994) to identify work settings in which fatal falls were likely to occur, and the risk factors that contributed to those falls. Eight thousand one hundred and two (8,102) workers were reported to have died as a result of falls from elevations during the 15-year period. The construction industry accounted for 4,044 of those deaths, or roughly 50% of all fatal falls from elevations. Within the construction industry sub-group (NAICS 23611), the NTOF identified general contracting and roofing as the work setting with the highest risk factors for a fall from elevation, with 205 and 147 falls respectively. The purpose of this study is to examine the effect that locomotion on an inclined surface has on flat surface postural stability. All subjects who volunteered as participants (n=20; males,) were tested under two walking conditions: flat surface and inclined walking on a 12 times 15' pitched roof segment to determine if there was a difference in sway velocity following exposure. Data were collected over four, ten-second trials, under eyes open and eyes closed conditions. Performance was measured using the recordings made by the NeuroCom Balance Master® System. Balance was recorded in sway velocity (degrees/second), where the value was representative of the change in center of gravity (COG) in the anterior, posterior, medial, or lateral directions. The angular change of the COG per unit time was summed and divided by ten-seconds to achieve an average sway velocity of the COG. These data were evaluated using a 2 (pre/post) × 2 (eyes) × 2 (flat walking, inclined walking) within-subjects repeated measures analysis of variance (ANOVA), with the dependent variable being sway velocity (deg/sec). Paired sample t-tests served as post hoc analysis. The analysis concluded that the average sway velocity of the COG resulted in a significant main effect following the inclined walking task: p ≤ .001. The findings have practical implications when dealing with the construction industry. On a daily basis, roofers ascend and conduct roofing related tasks for prolonged periods of time. Following exposure to the pitched roof setting, roofers must move from the roof to scaffolding or a ladder to descend. These findings suggest that there is a significant decrement in postural stability due to exposure to inclination. Postural stability is critical in ascending and descending ladders and scaffolding on flat surfaces. Possible areas of future research that might impact postural stability could potentially involve roof jacks, work boot design, and work rest cycles.