[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#: 275.28/KK9
Topic: D.17.a. Kinematics and muscle activity
Title: Human coordination variability and postural task performance
Authors: *E. G. JAMES 1 , K. M. NEWELL 2 ;
1 Pennsylvania State Univ., University Park, PA; 2 Kinesiology, The Pennsylvania State Univ.,
University Park, PA
Abstract: Previous research from the dynamic systems perspective has found that the human
motor system maintains standing posture in the face of internal or external perturbations through
the use of inphase and antiphase ankle-hip coordination pattern attractors. During a tracking task
involving postural sway, these ankle-hip coordination patterns have been found to emerge from
task and organismic constraints. In previous research the variability of these coordination
patterns has not been explicitly examined in relation to the level of task performance. Also, some
subjects have not produced a modally distributed ankle-hip coordination pattern, with the data
from these subjects being excluded from further analyses.
This study examined the relation between ankle-hip coordination variability and task error while
performing a postural tracking task at two movement frequencies. Subjects stood with arms
folded across the chest and were instructed to move their head in an anterior-posterior direction
to track the movement of a target projected onto a screen. Head movement was measured
through the use of a string-potentiometer while hip and ankle movements were measured with
electrogoniometers. The target oscillated at an amplitude of 10 cm and frequency conditions of
0.15 and 0.75 Hz were performed.
Significantly lower task error was produced in the 0.15 Hz tracking task condition than in the
0.75 Hz condition. Also, in the 0.15 Hz condition a significantly negative correlation was found
between ankle-hip relative phase and task error, indicating that better task performance was
associated with greater coordination pattern variability. This demonstrates the motor system‟s
use of multiple redundant strategies, rather than a fixed coordination pattern, to satisfy motor
task demands. This indicates that a less stable attractor within the human motor system can
produce greater functional task performance than a more stable attractor.
Disclosures: E.G. James , None; K.M. Newell, None.
Poster