Joint Kinetics and Muscle Activity While Walking on Ballast

Objective: This study examined the impact of two common sizes of ballast on gait biomechanics. The terrain was designed to simulate a railroad work setting to investigate the variation in gait kinetics and muscle activation while walking. Background: Research and epidemiology suggest a potential link between walking surface characteristics and injury. However, few studies have investigated the impact of ballast surfaces, which is a surface of interest in the railroad and construction industries, on gait dynamics. Method: For this study, 20 healthy adult men walked along three distinct pathways (no ballast [NB], walking ballast [WB], and mainline ballast [MB]). WB and MB consisted of rock with an average size of 0.75 to 1 in. and 1.25 to 1.5 in., respectively. Full-body motion, ground reaction forces, and electromyographic (EMG) signals from lower extremity muscles were collected, and three dimensional joint moments were calculated. Parameters of interest were moment trajectories and ranges, EMG activity, and temporal gait measures. Results: Joint-specific differences indicate significant variations between surface conditions. Joint moment ranges were generally smaller for MB and WB compared with NB. EMG activity, in particular, co-contraction levels, was found to be significantly greater on ballast compared with NB. Temporal gait parameters were significantly different for MB than for either WB or NB. Conclusion: Walking on ballast increases muscle activation to control the moments of the lower extremity joints. Application: The results suggest that ballast has an effect on muscles and joints; thus, the findings provide insight to improve and develop new work practices and methods for injury prevention.