Abstract
Bacgkground: The visual system acts as a feedforward control mechanism during human locomotion. Visual information contributes coordination of the head-arm-trunk (HAT) segment and modulating foot placement. The purpose of this study was to examine the effects of a complex navigational stone-stepping task on HAT segment control and how the visual system guides locomotion during a complex foot placement task. Methods: Nine university-aged females (Mean age: 22.5 years old +/-1.75) participated in this study. Participants were outfitted with four rigid bodies and two IRED markers in order to measure kinematic data, as well as an ASL H7-HS High Speed Head Mounted Optics eye tracking unit to assess gaze behaviour. Participants performed 40 trials across four conditions (e.g. predetermined and self-selected pathways; starting with either the left or the right foot), on a 7.2mx1.2m raised-target platform. Measurements were compared across conditions (e.g. constrained versus unconstrained), time points (e.g. first, middle, and last trial performed of each condition), and segment (one versus two). Results: Findings revealed that there was a significant difference between conditions such that: 1) the constrained vertical pupil RMS velocity was higher than the unconstrained (F(3,24)=4.71; p= .04; d=.46); 2) the unconstrained horizontal pupil RMS velocity was higher than the unconstrained (F(3,24)=4.40; p= .03; d=.36); 3) the constrained average walking speed was greater than the unconstrained (F(3,24)=23.27; p=0.04; d=.30); 4) the constrained trunk pitch was greater than the unconstrained (F(3,21)=4.84; p=0.01; d=.45); and 5) the unconstrained dynamic stability margin minimum was greater than the constrained (F(3,21)=4.89; p= .01; d=.41). Conclusions: During constrained trials, there was evidence to suggest that trunk control had a greater regulation than during unconstrained trials. However, during unconstrained trials, individuals were able to choose footholds based on their current state of stability. Thus, conditional demands influenced gaze behaviour, separating eye movements into vertical or horizontal components.
Meeting abstract presented at VSS 2016