Isotonic and isometric contractions exert the same amount of corticomotor system excitability in healthy subjects and patients after stroke

Abstract

Active, voluntary training of the centrally paretic upper limb is crucial for functional recovery after brain damage. The aim of this study was to determine whether the type of voluntary contraction has a differential influence on corticomotor system excitability in healthy subjects and patients after stroke. Experimental cross-sectional study. Fifteen healthy volunteers and 15 patients after stroke. Participants performed dynamic isotonic and isometric voluntary wrist extensions with the non-dominant or the paretic hand, respectively, with force levels of 10%, 20% and 30% of the maximum voluntary surface electromyogram. Excitability was measured by comparing the amplitude of motor evoked potentials elicited by transcranial magnetic stimulation. The type of contraction did not have any effect on the amplitude of motor evoked potentials, either in healthy subjects or in patients after stroke. Dynamic isometric and isotonic voluntary contractions seem to have the same effect on the excitability of the corticomotor system.