Walking biomechanics on a sloped residential roofing surface

Residential roofing work is among the riskiest occupations in the construction sector, partially because walking on a sloped roof surface may result in substantial biomechanical changes that are associated with the potential of increased instability. The objective of this study is to find whether typical roof working variables such as roof slope, walking direction, and footwear, affect the patterns of the ground reaction forces (GRFs) that may be critical to worker stability. Ten healthy male subjects participated in the study. Data were collected while subjects walked across a roof simulator that was set at three different roof slopes (0°, ~14°, ~27°). The subjects walked in four different directions (i.e., cross-slope in opposite directions and up-/down-slope) wearing three different footwear (i.e., two types of roofing-specific boots, one type of general work boot). The normal and shear components, as well as the resultant of the GRFs, were analyzed for each foot separately. The results indicate that a linear relationship exists between roof slope and normal/shear ground reaction forces. Cross-slope walking resulted in larger shear forces for the foot that was lower on the slope. An increase in roof slope angle generally resulted in a longer stride time when walking up/down slope. The findings show that various roof-working factors collectively influence GRFs and stride times when traversing a sloped roof surface, indicating that worker stability may depend on multiple interacting aspects.