Download Assessment of Physical and Muscular Accommodations to

Assessment of Physical and Muscular
Accommodations to Repeated Potentially Destabilizing
Anterior Horizontal Translations
Kathryn Kearns1, Frank Hensing2, John Huss3, Jeff Taylor4, Charles
Robinson5, 6
1 – Department of Chemical & Biomolecular Engineering, Clarkson
University, 2 – Department of Mechanical & Aeronautical Engineering,
Clarkson University, 3 – University of Minnesota, 4 – SUNY Canton , 5
– Center for Rehabilitation Science, Engineering & Technology,
Clarkson University, 6 – Research Service, Syracuse VA Medical
Center, Syracuse, NY, USA
Determining how an individual responds to a perturbation is valuable in attempting to understand how
different populations will respond to an event that may result in a fall. The standard method of assessing
response is to subject a client to repeated perturbations such that their response can be averaged.
However, it has been observed that clients significantly modify their response to the perturbation within a
few trials as they physically prepare to resist the perturbation. Understanding the nature of these
accommodations is critical in determining the legitimacy of the data gathered in repeated trials. In the
current work, data from the first three trails of a superthreshold perturbation were compared
(superthreshold involved an anterior perturbation of 4 mm at 100mm/s2 – a movement easily detectable
by all clients) as well as three trials of a supersuperthreshold perturbation (an anterior perturbation of 50
mm at 1000mm/s2). To assess changes in the clients overall center of mass, the anterior-posterior center
of pressure was determined. Muscular response to the movement was noted primarily by the response of
the tibialis anterior and gastrocnemious. It was found that the most reliable and consistent
accommodation was a shift in center of pressure anteriorly – into the movement. This shift was typically
fully engaged by the second trial, and was approximately half of the maximum change in center of
pressure during the initial perturbation. It was found that after the initial trial, subjects did accommodate
and altered their center of pressure.
2012 Chemical Engineering, Center for Rehabilitation Engineering Science and Technology, Dr. Charles
Robinson