Early activation of ankle muscles following unexpected light touch displacement at the fingertip during treadmill walking

• Author / Creator

  Shiva, Tania

• Lightly touching a stable surface has been shown to reduce sway in people standing with their eyes closed. Recently, it was shown that if this surface is unexpectedly moved, some people will react with a sway in the opposite direction, consistent with a balance correction. However, this balance correction is only seen following the first trial and in only about 60% of participants. One possible reason for the inconsistent expression of these responses might be that the touch-related feedback is not interpreted as a critically relevant input when standing on a stable surface. To increase the relevance of the touch-related feedback, participants were asked to walk on a treadmill with their eyes closed, a task that cannot be performed without provision of a spatial reference such as with touch. It was hypothesized that unexpected displacement of the touch reference would evoke responses more consistently across participants and with repeated touch displacements when touch is critically relevant to the performance of the task, such as when walking on a treadmill without vision. Twenty participants received 10 unexpected touch displacements delivered at right heel strike while walking on treadmill with eyes closed. Ten participants received forward touch displacements, while the other 10 received backwards displacements. All 20 participants responded to the touch displacements with activation of muscles at the ankle, suggestive of a corrective response. In particular, all participants responded to multiple trials of the disturbance. This is in contrast to what was seen during standing where participants reacted to the initial disturbance, but did not respond to any subsequent trials. However, the number of participants that reacted to the initial disturbance during walking was not different than what was seen during standing. These results suggest that sensory information related to the touch reference can be incorporated into the control of balance and stability during walking. However, the inconsistency in the expression of the evoked responses suggests that the contribution of this feedback is modulated within the context of the ongoing task and the other available sensory feedback, despite the critical importance of the touch reference to maintaining position on the treadmill.

• Subjects / Keywords

  • Balance correction
  • Treadmill walking
  • Unexpected light touch displacement

• Graduation date

  Fall 2017

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R36Q1SX2X

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.