Plantar vibration effects on postural balance at elevation.
Simeonov-P; Hsiao-H; Powers-J; Ammons-D; Amendola-A; Kau-T-Y
NOIRS 2008-Abstracts of the National Occupational Injury Research Symposium, October 21-23, 2008, Pittsburgh, Pennsylvania. Morgantown, WV: National Institute for Occupational Safety and Health, 2008 Oct; :A1.4
Introduction: The risk of falls from height on a construction site increases in conditions degrading workers' postural control. At elevation, workers depend heavily on sensory information from their feet to maintain balance. Recent research suggests that low levels of mechanical vibration to the feet may be beneficial for balance control. This study investigates two hypotheses: (1) sensory-enhancement - undetectable (subthreshold) mechanical vibration at the feet improves worker's balance at elevation, (2) sensory-suppression--detectable (suprathreshold) mechanical vibration degrades worker's balance. Methods: Twelve construction workers were tested while standing in different postures on instrumented insoles, which applied subsensory and suprasensory levels of random mechanical vibration to the feet. The tests were conducted in a virtual reality system simulating balance-challenging construction environment - i.e., a narrow plank on a residential structure. Upper body kinematics was assessed with a motion-measurement system. Postural stability effects were evaluated by conventional, "random walk," and angular-displacement sway measures. Results: The analysis did not confirm the "sensory-enhancement" hypothesis, but provided evidence for the "sensory-suppression" hypothesis. The results indicated that plantar-vibration effects were significantly modified by posture. Subsensory vibration slightly reduced some sway measures in the standard posture but significantly increased them in the semitandem posture. Suprasensory vibration increased some sway measures across all conditions; however, the increase was considerably larger in the semitandem posture and affected most of the sway variables. Conclusions: Sensory suppression associated with detectable levels of mechanical noise to the feet may increase the risk of losing balance. Workers on an elevated construction site might be at increased risk of falls if they can detect vibrations under their feet. To reduce the risk of losing balance, mechanical vibrations in the supporting structures should be minimized when performing tasks at elevation.
Accident-prevention; Accidents; Construction-industry; Construction-workers; Control-technology; Engineering-controls; Ergonomics; Injury-prevention; Posture; Sensory-perceptual-processes; Vibration; Vibration-effects
NOIRS 2008-Abstracts of the National Occupational Injury Research Symposium, October 21-23, 2008, Pittsburgh, Pennsylvania