[Abstract Title]. - Society for Neuroscience

Poster
275. Posture: Kinematics and Muscle Activity
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 275.13/JJ28
Topic: D.16.d. Kinematics and Muscle Activity
Support: Natural Sciences and Engineering Research Council (NSERC)
Title: Balance corrective responses associated with arm perturbations during treadmill
locomotion
Authors: *J. FORERO, J. MISIASZEK;
Univ. Alberta, Edmonton, AB, Canada
Abstract: It has been shown that the arms play an important role when balance corrective
strategies are to be used; leg muscle responses are altered depending on whether hands are
touching, grabbing or holding an object. Rapid balance reactions during walking are also
required when perturbations to balance are delivered through the arms (Nashner and
Forssberg1986). However, unlike the legs, the arms are not required to participate in locomotion
or maintaining balance, but may be simultaneously engaged in other activities during walking.
We hypothesized that balance reactions induced by perturbations applied through the arms
depend upon the task conditions at the time of perturbation. To test this, seven subjects were
asked to hold a set of handles while walking on a treadmill. Forward and backward perturbations
were delivered to the handles at four different phases during the step cycle. Subjects were asked
to A) react to the perturbation as quickly as possible and return to the starting arm posture, or B)
be compliant and allow the handles to be displaced. Muscle activity was recorded from the
Tibialis Anterior (TA), Soleus (SOL), Vastus Lateralis (VL), Biceps Femoris (BF), Anterior
Deltoid (AD), Posterior Deltoid (PD), Biceps Brancii (BB) and Triceps Brancii (TB).
Electrogoniometers recorded joint angles of the knee, ankle and elbow. Displacement of the
handles and forces applied to the handles were also recorded. Responses to the perturbations
were only evoked in either the leg or arm muscles when subjects were instructed to react to the
perturbations. Therefore, displacement of the handles themselves was not a sufficient event to
trigger a corrective response, in either the arm or leg muscles. Moreover, the evoked responses in
the react condition were characterized by responses in the leg muscles preceding those of the
arms, despite the locus of the perturbation. The implication is that the balance maintenance
demands of the task supersede the arm task as the balance correction occurred prior to the arm
correction. Furthermore, because the muscle activation pattern is present only during the react
condition and occurs before the body gets perturbed from its rhythmic movement, evidence of a
program being activated and deactivated depending on the task is presented.
Disclosures: J. Forero, None; J. Misiaszek, None.