If It's Not a Slip, Trip, or Fall,
What Is It?
Biomechanics of Walking on Railroad Ballast
Robert O. Andres, Ph.D., CPE
Ergonomic Engineering, Inc.
20 Gulf Rd.
Pelham, MA 01002
Kenneth G. Holt, Ph.D., PT
and Masayoshi Kubo, MS, PT
Barreca Motion Analysis Laboratory
Boston University
Department of Physical Therapy
635 Commonwealth Ave
Boston, MA 02215
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Paper Presented at the Proceedings of International Conference on Computer-Aided Ergonomics and Safety (CAES 2001), Maui, Hawaii, July 29-August 1, 2001
Abstract
Five healthy male subjects (mean age = 31.8 yr, mean height = 181.4 cm, mean weight = 83 kg) walked on level concrete, yard ballast (rock about 1.9 cm across), and mainline ballast (3.8 cm) while their rearfoot motion measured. The ballast was placed in trays (4.9 m long, 0.9 m wide, 20 cm deep) that were tilted 7 degrees in the transverse plane. Rearfoot motion was measured by an Optotrak system while the subjects walked the length of the trays wearing work boots. Standard biomechanical techniques were used to acquire and process the rearfoot data. A repeated measures ANOVA and a subsequent multiple comparison test revealed that the rearfoot range of motion was significantly greater walking on the mainline ballast than walking on either the yard ballast or the concrete. In fact, the mean range of rearfoot motion for yard ballast was not significantly different from that resulting from walking on concrete. Variability was more than twice as great walking on mainline ballast than walking on level concrete. Rearfoot angular velocities walking on level concrete and yard ballast were not significantly different, but both were significantly less than walking on mainline ballast. These data confirm that railroads should place smaller (yard) ballast in locations where trainmen have to walk as part of their jobs.
1. Introduction
Railroad workers required to walk on ballast experience slips, trips and falls, but they have also been developing lower extremity musculoskeletal disorders (MSDs). Trainmen work in railroad yards or on the road to make-up trains, inspect cars, and drop off or pick up cars at industrial sites. A significant portion of their work day involves walking on ballast – the rock that is laid down to support the rails and provide drainage. Ballast rock comes in different sizes and railroads have established guidelines for ballast size specifying smaller ballast to be used in the yards where more walking takes place. This study was an investigation into the mechanisms of loading of the lower extremity that could lead to MSDs even when slips, trips, or falls don’t occur. The testing quantified rearfoot motion of subjects walking under different conditions that represent typical walking tasks of railroad workers. Rearfoot motion has been used to test the differences between shows (Greer et al., 1987), the effects of ankle supports (Hamill, Morin, Clarkson, and Andres, 1988), and other investigations of lower extremity function (Campell et al., 1987; De Wit et al., 2000).