BACKGROUND: Sea travel leads to well-known changes in gait, but these effects have not been evaluated using quantitative data obtained through controlled experiments. We obtained quantitative data on step-timing patterns as experienced maritime crewmembers walked on a ship at sea.METHODS: Using a within-subjects design, crewmembers walked back and forth along straight line paths (11 m long) that were parallel with the ship’s long (i.e., fore-aft) and short (i.e., athwart) axes. Using contact switches attached to the feet, we measured temporal parameters of gait, including stride time, the variability of stride time, and the coefficient of variation. We also evaluated the temporal dynamics of stride times using detrended fluctuation analysis.RESULTS: The variability of stride time differed between walking fore-aft (mean = 0.10 s) and walking athwart (mean = 0.28 s). The coefficient of variation also differed between walking fore-aft (mean = 11%) and walking athwart (mean = 43%).CONCLUSIONS: We obtained direct evidence that ship motions in roll and pitch differentially affect the timing of stepping patterns in human gait. This novel finding motivates new research on quantitative parameters of gait at sea.Haaland E, Kaipust J, Wang Y, Stergiou N, Stoffregen TA. Human gait at sea while walking fore-aft vs. athwart. Aerosp Med Hum Perform. 2015; 86(5):435–439.