Perception of Safe Horizontal Reaching Distance Changes with Repetitive Occupational Loading in Novice Lifters

Safe work behaviours rely on accurate perceptions of injury risks, and workers who have a misperception of risk can be injured. Despite the importance of perception-action coupling, little is known about modification of those perceptions with changing physical or cognitive STATE. It is hypothesized that changing values for perceived affordances could evidence these modifications. A better understanding of how worker characteristics (e.g., level of fatigue) affect perceptions of affordance and their corresponding behaviours, may help when developing strategies for ergonomic best practices, particularly in manual material handling (MMH) activities. The aim of this study was to compare safe perceptions of affordance from workers that completed repetitive STATE loading. Seventy-five novice MMH workers (23 male; mean age = 21.43, SD = 3.24) made perceived affordances of their safest horizontal reaching distance (acceptable limit) to complete a model task. STATE loading consisted of physical or cognitive fatigue or a control. The levels of fatigue were assessed at five-minute intervals using Ratings of Perceived Exertion (RPE) values and Multi-Fatigue Inventory (MFI) values, respectively. A significant main effect of TIME indicated a decrease of perceived safest reaching distance observed from baseline through subsequent measurements (p