Visual Perception of Slips and Falls
Woo-Hyung Park, Ph.D. Dissertation, Human Posture Control: Preparation Gait to Avoid Slips and Falls, May, 2004
This project examines the visual perception component that may contribute to whether a person slips or falls when they
encounter a slippery surface. Texas Tech has been one of the premier institutions for examining slips and falls for a number of years. The emphasis of our research is moving beyond the detailed description of the slip/fall event and looking closely at the factors which comprise the person's preparation process before a slip or fall occurs.
Many factors contribute to the probability of occurrence of a slip or fall. The conjecture of this study is that the degree of human perception of the surface slipperiness is among those factors. In addition, it is hypothesized that the surrounding environment (ceiling height, room width and orientation, lighting intensity and arrangement, etc.), and not only the floor surface, contributes to the human perception of the surface slipperiness. Due to the impracticality of conducting such a study with many environments, the researchers studied the applicability of performing the tests in a virtual environment. In a dark and completely enclosed space (2m 2.5m 2.5m), the subjects were presented with graphical images of different environments on a computer monitor and asked to evaluate the slipperiness of the surfaces in the images. The subjects were made to believe that the actual floor surface on which they were standing was changed with the changing of the images, and were also asked to evaluate the slipperiness of the actual floor. There was a noticeable difference in the subjects perception of the floor slipperiness throughout the trials regardless of the fact that the floor was never changed. The use of virtual environments is therefore verified as an accepted method of slips and falls testing in a limited laboratory environment.
Slip Video1 | Slip Occurs | Slip Video 3
The figure above shows the key components of our slip/fall track and arresting system that is used during many of our slip fall experiments.
When we encounter a slippery surface, what should we do?
The objective: maintain balance and minimize slip distance
To accomplish this: (1) reduce step frequency, (2) shorten step length, and (3) lower the center of mass of the body.
Questions
- Why is the gait strategy mentioned above useful for adapting to the slippery surface?
- How do we prepare to step onto a slippery surface?
- Are there any differences in adaptation gait strategy between younger and old people?
- In order to investigate this topic, we must know what human gait is, how the human controls body segments, and how the human interacts with the environment.
- We are interested in (1) the dynamics of human movements and (2) how to apply knowledge of human dynamics to help people.
If you would like more information regarding the current slip/fall research, please contact Dr. Simon Hsiang.