2021 Volume 45 Issue 3 Pages 172-178
The purpose of this study was to clarify the characteristics of toe trajectory when stepping over an obstacle in the dark and the effect of light information．In this study, time series data of toe trajectory of leading foot in sagittal plane (antero-posterior direction and vertical direction) were measured from eight young adults while they stepped over an obstacle under two illuminations (Blight and Dark) and three light information by phosphorescence (with the phosphorescence materials applied to the overall and partial and without the phosphorescence materials) conditions．Principal component analysis has been applied on the 240 x 202 input matrix constructed from participant’s time-normalized toe trajectory data． Two-way (illumination conditions by obstacles) multivariate analysis of variance on the principal component scores of extracted principal component vectors (PCV) revealed the effect of significant illumination condition on PCV1(p<0.05), 3(p<0.001) and 6(p<0.05)．There were no effects of light information by phosphorescence and the interaction of illumination and light information．Reconstructed toe trajectory from PCVs indicate that participants tend to take off their toe father away from the obstacle, land their heel closer to the obstacle, and lift their toe higher in the dark condition．We further analyzed these discrete parameters statistically, and found significant differences between blight and dark conditions．Also, we analyzed take off distance, heel contact distance and toe clearance．These results were similar to those of the PCA．In conclusion, the characteristics of toe trajectories when stepping over an obstacle were different in dark and light conditions, and no effect of light information on toe trajectories was found in dark conditions．
