Posture in XXXX : impairment of reflexes and programming.

@entity1 @entity935 @entity191 @entity1767 @entity121
The leg muscle electromyographic responses induced during stance by impulsive displacements of a treadmill belt (directed forward or backward and at different rates) were studied in a group of @entity1 with @entity191 and a group of age-matched healthy subjects. Young normal subjects were also studied both before and after intake of a @entity935 antagonist ( @entity1767 ). Compensatory gastrocnemius electromyographic responses resulting from backward-directed displacements were significantly smaller in both the @entity1 and the young normal subjects following intake of @entity1767 . The reduced sensitivity of the gastrocnemius muscle to stretch correlated with an inability to compensate for the perturbations. In the @entity1 , the gastrocnemius response was followed by enhanced activation of the tibialis anterior muscle. This was not the case in the normal subjects after intake of @entity935 antagonist and is probably not, therefore, the consequence of acute @entity935 deficiency. In the @entity1 the angular rotation at the ankle joint induced during faster backward-directed displacements was slower than that in normal subjects, despite identical amounts of gastrocnemius electromyographic activity. This supports earlier findings of changes in intrinsic @entity121 in @entity191 . None of these differences were seen when the tibialis anterior muscle was stretched. This differential behavior of the antagonist leg muscles can best be explained by the different function fulfilled by these muscles in regulation of stance and gait.
