The Effect of Noise on Gait Synchronization to a Vertical Oscillating Treadmill

Introduction: Sensory motor synchronization plays a critical role in the ability to synchronize to an entrainment stimulus. When walking, individuals often entrain their stride to an external stimulus. However, entrainment often leads to a reduction in the magnitude and structure of stride variability, which may not be beneficial in a rehabilitation setting. Therefore, the purpose of this study was to examine the effects of random variation in the cycle period of an oscillation walkway on gait synchronization and movement variability. Methods: 16 participants walked on an oscillating treadmill for 17 trials lasting 10 minutes each. 8 trials were at participants step frequency and 8 were at step frequency +3%. Each trial consisted of a different amount of allowed variation of cycle period of treadmill oscillation (0%-25%). Magnitude and stability of synchronization was recorded along with magnitude and structure of stride variability. Results: Levels of noise (i.e. variability) that were 15% or greater led to a significant decrease in the magnitude of synchronization (P<.003) and stability of synchronization (P<.003). Stride variability increased significantly for levels of noise that were 10% or greater (P<.003). Discussion: Large amounts of noise were shown to significantly reduce gait entrainment. However, small amounts of noise appeared to improve gait entrainment, though these changes were not statistically significant. This research suggests that changes in noise levels of an external stimulus will influence gait entrainment and movement variability, and may hold implications for gait entrainment therapy.