Effect of Stair Tread Width on Perception of Vertical Ascending Distance

This study aimed to investigate the relationship between stair tread width and the perception of vertical movement distance during stair ascent.The experiment tested whether variations in stair tread width (300mm, 600mm, and 900mm) influenced the perceived vertical movement distance. Twenty healthy university students participated, ascending a five-step stair constructed in the real world while wearing a head-mounted display (VIVE Focus Vision/HTC). The head-mounted display presented an immersive virtual environment where virtual stairs were aligned with the actual physical stairs. This setup controlled visual input while allowing participants to perform physical stair-climbing motions.Previous studies have proposed reproducing the sensation of stair ascent using virtual environments with only horizontal walking. However, horizontal movement alone lacks the muscle activity and physical effort associated with stair ascent, which may affect the perception of vertical movement. To address this limitation, this study utilized real stairs to test the validity of the effort hypothesis.During the experiment, participants repeatedly ascended the target stairs. After each ascent, the stairs were temporarily hidden, and a ground plane—set at ground level—was displayed as the measurement space. A single cylinder was shown on the ground, which participants could adjust in height using a controller. They were instructed to adjust the cylinder's height to match the height of the stairs they had just climbed. The adjusted height of the cylinder was recorded as the "perceived height," quantifying the ascending sensation induced by the stairs.A one-way ANOVA with stair tread width as the factor, followed by multiple comparisons, revealed statistically significant differences (p < 0.10) between the 300mm and 600mm conditions and between the 300mm and 900mm conditions. In both cases, the perceived height was greater for the 300mm tread condition, suggesting that smaller tread dimensions enhanced the sense of ascent.These findings are consistent with the effort hypothesis. The 300mm tread condition resulted in steeper gradients than the other conditions, requiring greater effort per unit of horizontal movement. The findings suggest that this increased effort contributed to the heightened perception of vertical movement distance.In conclusion, this study demonstrates that altering stair tread width can influence the perceived height, providing insights into how physical effort affects perception in stair-climbing tasks.