Ground reaction force adaptation during cross-slope walking on railroad ballast

Background: : Walking on railroad ballast is a unique challenge for railroad workers and contributes to a large number of falls and slips. However, the characteristics of ground reaction force (GRF) when walking on ballast combined with a cross-slope condition are poorly understood. Research question: : How does the magnitude and temporal distribution of GRF change during walking on railroad ballast combined with a cross-slope condition? Methods: : Eight experienced railroad workers walked with their self-selected speed on three surfaces (mainline ballast, walking ballast and no ballast) in both a level and cross-slope (7 degrees) condition. The magnitude and time of occurrence of selected key features of the GRF were extracted from the force plate. A two-factor repeated measures ANOVA was used to determine the effect of surface and cross-slope condition. Results: : The minimum anteroposterior GRF and the first peak of the normal GRF occurred earlier on mainline ballast and walking ballast than no ballast. The maximum anteroposterior GRF was smaller, but the first peak of the normal GRF was larger on walking ballast compared with no ballast. Additionally, the asymmetrically mediolateral GRFs were observed between upslope limb and downslope limb in the cross-slope condition, which were also significantly different from the level condition. Significance: : Ballast combined with a cross-slope condition posed a higher requirement for dynamic control to prevent downslope slippage and body instability, which could increase the fall risk for railroad workers. Future studies should investigate interventions to improve dynamic balance and reduce foot slippage on ballast.