Effects of upper and lower limb static exertions on global synkineses in hemiparetic subjects

Objectives: Global synkineses are nonpurposive pathological involuntary mus cle activities or movements elicited at several or ail of the joints of the affected limb or limbs during voluntary forceful resisted contractions. Th e purpose of this study was to assess the effect of upper and lower limb ex ertions on manifestations of upper limb global synkineses in hemiparetic su bjects. Design: Involuntary muscle activities on the affected upper limb of 11 hemi paretic subjects and on the left or right upper limb of 10 control subjects were recorded using surface electromyography during successive bilateral m aximal ankle exertions and during contralateral grips. Results: Significant differences in the level of involuntary electromyograp hy (EMG) activities were observed between experimental conditions (ANOVAs, p < 0.05). EMG levels in hemiparetic subjects were significantly higher dur ing contralateral grip tasks than during the ankle exertions. Conclusion: These results suggest that upper limb global synkineses are mor e prevalent in specific tasks and that this task specificity may reflect th e neurophysiological mechanisms involved in the generation of global synkin eses.