Effects of upper limb unilateral isometric efforts on postural stabilization in subjects with hemiparesis

Objective: To characterize postural stabilization during a progressive unilateral isometric abduction of the upper limb in a seated position in healthy subjects and subjects with hemiparesis. Design: Convenience sample. Setting: University secondary care rehabilitation center. Patients: Twelve patients with hemiparesis and 12 subjects without neurologic disorder. Interventions: Subjects were seated on a forceplate, with forearms fixed in cuffs mounted on a force transducer, Two trials per side of isometric abduction of arm were conducted. The orthogonal force and torque exerted was measured for each arm. Main Outcome Measures: Forces at the upper limbs and at the seat, global motor performance, spasticity of upper limb, grip force, and dexterity. Results: Results of analyses of variance showed differences in the magnitude of the contralateral limb forces generated by subjects with hemiparesis and healthy subjects (p < .05). Normalized contralateral forces in the nonparetic upper limb associated with paretic isometric efforts were higher than those associated with nonparetic efforts and higher than those associated with efforts in healthy subjects. Conclusion: These results suggest that postural stabilization during isometric efforts is impaired in subjects with hemiparesis.