OCCUPATIONAL APPLICATIONS We found, contrary to expectations, that performing a fatiguing simulated heavy manual material handling (MMH) task did not adversely affect the risk of trip-induced falls when compared to a less-fatiguing light MMH task. However, when considering these MMH tasks together rather than in comparison, our results provide evidence for adverse effects of fatigue on both gait and the ability to recover balance after tripping. The current results provide additional evidence that physical fatigue increases fall risk, start to clarify the mechanisms by which this increase occurs, and can help in developing and evaluating fall prevention strategies targeting these mechanisms.
Keywords: Slips, trips, and falls; fatigue; manual material handling.
TECHNICAL ABSTRACT Background Falls are a leading cause of occupational injuries, and the incidence of occupational falls may be exacerbated by physical fatigue resulting from physically-demanding work. Purpose: The goal of this study was to evaluate the effects of occupationally-relevant physical fatigue on the risk of trip-induced falls. Methods: Thirty-six healthy young adults performed two-hours of a simulated heavy manual material handling (MMH) task (experimental group) or a light MMH task (control group). Risks of tripping and slipping were evaluated before and after completing the task, and one laboratory-induced trip while walking was induced after completing the MMH task. Results: Compared to the light MMH task, the heavy MMH task did not adversely affect the risk of tripping or slipping during gait, reactive balance after tripping, or fall rate after tripping. These results may have been due to an insufficient difference in fatigue level between groups. When both groups were considered together, however, the MMH tasks resulted in an unsteady gait, an increased risk of slipping while walking and carrying a load, and a fall rate that was substantially higher than reported in other studies. Conclusions: Although the effects of the heavy and light MMH tasks did not differ, changes in fall risk measures when considering both MMH tasks as one provide evidence for the biomechanical mechanisms by which physical fatigue may increase the risk of occupational falls.