Right-Hand Forces in Ingress

Reed, M.P., Hoffman, S.G., and Ebert-Hamilton, S.M. (2010). Hand positions and forces during truck ingress. Proceedings of the 2010 Human Factors and Ergonomics Society Annual Meeting. HFES, Santa Monica, CA.

Objective: Quantify the peak force exerted by the right hand on the handhold during the initial phase of egress.

Method: The resultant right-hand force magnitude was computed from the three orthogonal reaction force components measured on the external handhold.

Results: Resultant handhold force was not significantly related to body weight, stature, or BMI within or across step conditions. The small number of female subjects precluded an investigation of gender effects. The overall average hand force was 233 (67) N, or 25 (7) percent of body weight. An interaction was observed between resultant force magnitude and step condition. The figure below shows means and standard errors for handhold forces by step condition. For all step conditions, the mean external handhold force is larger than the mean internal handhold force. A paired t-test by step condition showed that the mean external handhold force was larger than the internal handhold force (p<0.01) for step conditions 1, 2, 7, and 8. Significant differences occurred for step conditions in which the lower step was farthest from the handhold. In step conditions with a large lateral extent (lower step > 350 mm outboard of the door sill), the mean hand force magnitude with the external handhold was an average of 37 N (18%) higher than with the internal handhold.