Human Gait at Sea While Walking Fore-Aft vs. Athwart

Abstract

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.

Dynamic perception of dynamic affordances: walking on a ship at sea

“…The difference was in the expected direction (athwart performance > fore-aft performance), consistent with the hypothesis that the control of lateral oscillation was more greatly challenged when walking fore-aft than when walking athwart. This result is consistent with an earlier finding that step timing is more strongly affected by ship motion in roll than by ship motion in pitch (Haaland et al 2015) and is consistent with similar effects in the context of standing body sway (Chen and Stoffregen 2012; Munafo et al 2015; Varlet et al 2015). It is important to emphasize that these effects do not suggest a differential effect of roll versus pitch motion, as such.…”

“…At sea, the kinematics of upright stance are powerfully affected by facing fore-aft versus athwart (Chen and Stoffregen 2012; Munafo et al 2015; Varlet et al 2014, 2015). In addition, in walking on a ship at sea the timing of footfalls differs between walking along the ship’s fore-aft versus athwart axes (Haaland et al 2015). In the present study, we asked whether the fore-aft/athwart distinction would alter the distance that mariners could walk along a narrow path (i.e., the affordance for maintaining dynamic gait within a narrow path), and whether experienced mariners would be sensitive to these differences in a prospective manner.…”

Experimental study on individual walking speed during emergency evacuation with the influence of ship motion

“…When roll>pitch and walking along the ship's short axis or athwartship, the maximum walkable distance in the specified path should be greater than when walking along the ship's long or fore-aft axis. When pitch>roll, this relationship should be reversed (Haaland et al, 2015;Walter et al, 2017;.…”

“…During voyage, when people stand in athwartship and fore-aft directions, the kinematics of the upright posture is very different to achieve (Varlet et al, 2015;Walter et al, 2019). Also, when walking on the ship, such as walking along the athwartship or fore-aft axis of the ship, the time intervals of gait and stride are different (Haaland et al, 2015). Therefore, the analysis of athwartship and fore-aft walking speeds will predictably reflect the influence of ship motion on actual walking ability in these two directions.…”

“…1, a ship will oscillate in six degrees of freedom in the ocean, with the most common motions being roll and pitch. As the length of a ship is larger than its width, in general, its roll is greater than its pitch (Haaland et al, 2015;Walter et al, 2019). The impact of ship motion on individual walking is so obvious that those with experience onboard have observed that the "swing gait" of seafarers will continue for a while after returning to the land (Walter et al, 2017).…”