Article

The present study investigated the influence of mechanical constraints (load and
movement velocity) on the movement accuracy during a reciprocal aiming precision
task. Seven participants had to point rhythmically and alternatively (with
flexion-extension of the right elbow) a cursor at two targets as accurately as
possible. Two loads (applied to the limb effectors; 500 and 2500g), two movement
frequencies (1.25 and 1.75Hz) as well as two target sizes (1 and 5cm) were
manipulated. Surface EMG activity of both biceps brachii and triceps brachii was
recorded. Attentional demands, reflecting the central cost associated with the
performance of aiming movements was assessed using a dual-task paradigm (via a
probe reaction time task - RT). While the results demonstrated a significant
degradation of pointing accuracy with mechanical loading (mean absolute error -
AE for 500g load: 0.32mm+/-0.64; mean AE for 2500g load: 0.51+/-0.74mm), no
significant effect of movement frequency was found. For the two mechanical
constraints, the mental effort to meet the task demands remained the same (mean
RT(-500g): 370+/-123ms; mean RT(-2500g): 395+/-119ms). Electromyographic activity
of both biceps brachii and triceps brachii muscles evidenced neural adaptations
to changes in mechanical constraints. Put together, the present findings suggest
that the cause of the observed loss of movement accuracy may probably result from
more peripheral alterations such as an impairment of the afferent information
processing.
CI - Copyright (c) 2011 Elsevier Ltd. All rights reserved.

Langue : ANGLAIS