c'/'I,*j,'I;'., If It's ~Iot a Slip, Trip, or Fall, What Is It? Biomechanics of Walking on Railroad Ballast

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 was 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 ~5ystem while the subjects walked the length of the trays wearing work boots. Stclndard biomechanical techniques were used to acquire and process the rearfoot motion 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 signific:antly different, but both were significantly less than walking o