Abstract
Post-stroke patients usually exhibit reduced peak muscular torque (PT) and/or force steadiness during submaximal exercise. Brain stimulation techniques have been proposed to improve neural plasticity and help to restore motor performance in post-stroke patients. The present study compared the effects of bihemispheric motor cortex transcranial direct current stimulation (tDCS) on PT and force steadiness during maximal and submaximal resistance exercise performed by post-stroke patients vs. healthy controls. A double-blind randomized crossover controlled trial (identification number: TCTR20151112001; URL: http://www.clinicaltrials.in.th/) was conducted involving nine healthy and 10 post-stroke hemiparetic individuals who received either tDCS (2 mA) or sham stimulus upon the motor cortex for 20 min. PT and force steadiness (reflected by the coefficient of variation (CV) of muscular torque) were assessed during unilateral knee extension and flexion at maximal and submaximal workloads (1 set of 3 repetitions at 100% PT and 2 sets of 10 repetitions at 50% PT, respectively). No significant change in PT was observed in post-stroke and healthy subjects. Force steadiness during knee extension (~25–35%, P < 0.001) and flexion (~22–33%, P < 0.001) improved after tDCS compared to the sham condition in post-stroke patients, but improved only during knee extension (~13–27%, P < 0.001) in healthy controls. These results suggest that tDCS may improve force steadiness, but not PT in post-stroke hemiparetic patients, which might be relevant in the context of motor rehabilitation programs.
Highlights
Post-stroke patients often exhibit motor sequels (Langhorne et al, 2011) and hemiparesis (Prado-Medeiros et al, 2012) that are associated with increased variability in the application of force during motor tasks (Chow and Stokic, 2011)
The main purpose of the present study was to investigate whether motor cortex transcranial direct current stimulation (tDCS) would improve peak muscular torque (PT) and force steadiness during a gross motor task, in post-stroke hemiparetic patients compared to healthy controls
The main findings were: (i) Bihemispheric tDCS improved force steadiness in poststroke hemiparetic patients during unilateral knee extension and flexion, but only during knee extension in healthy controls; and (ii) No change in PT during knee extension or flexion in stroke and healthy groups were detected after tDCS
Summary
Post-stroke patients often exhibit motor sequels (Langhorne et al, 2011) and hemiparesis (Prado-Medeiros et al, 2012) that are associated with increased variability in the application of force during motor tasks (Chow and Stokic, 2011) This condition typically results in low force steadiness (Moritz et al, 2005) and poor movement control (Kornatz et al, 2005) that can tDCS and Force Steadiness in Stroke Patients negatively impact on the ability to perform activities of daily living (Timmermans et al, 2014). The effects of tDCS on the performance of tasks demanding submaximal and maximal strength, and force steadiness during exercise involving larger muscle groups of the legs are yet to be determined This would be useful, since the muscle strength of both lower limbs is related to activities of daily living
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