title: Transcranial Direct Current Stimulation of the Leg Motor Cortex Enhances Coordinated Motor Output During Walking With a Large Inter-Individual Variability.
abstract: BACKGROUND
  Transcranial direct current stimulation (tDCS) can augment force generation and control in single leg joints in healthy subjects and stroke survivors. However, it is unknown whether these effects also result in improved force production and coordination during walking and whether electrode configuration influences these effects.
  
  
  OBJECTIVE
  We investigated the effect of tDCS using different electrode configurations on coordinated force production during walking in a group of healthy subjects and chronic stroke survivors.
  
  
  METHODS
  Ten healthy subjects and ten chronic stroke survivors participated in a randomized double-blinded crossover study. Subjects walked on an instrumented treadmill before and after 10 minutes of uni-hemispheric (UNI), dual-hemispheric (DUAL) or sham tDCS applied to the primary motor cortex.
  
  
  RESULTS
  tDCS responses showed large inter-individual variability in both subject populations. In healthy subjects tDCS enhanced the coordinated output during walking as reflected in an increased positive work generation during propulsion. The effects of DUAL tDCS were clearer but still small (4.4% increase) compared to UNI tDCS (2.8% increase). In the chronic stroke survivors no significant effects of tDCS in the targeted paretic leg were observed.
  
  
  CONCLUSIONS
  tDCS has potential to augment multi-joint coordinated force production during walking. The relative small contribution of the motor cortex in controlling walking might explain why the observed effects are rather small. Furthermore, a better understanding of the inter-individual variability is needed to optimize the effects of tDCS in healthy but especially stroke survivors. The latter is a prerequisite for clinical applicability.
authors.affiliation: Department of Biomechanical Engineering, MIRA Institute for Biomechanical Technology and Technical Medicine, University of Twente, Enschede 7500 AE, The Netherlands. Electronic address: e.h.f.VanAsseldonk@utwente.nl.
authors.forename: Edwin H F
authors.initials: EH
authors.lastname: van Asseldonk
authors.affiliation: Department of Biomechanical Engineering, MIRA Institute for Biomechanical Technology and Technical Medicine, University of Twente, Enschede 7500 AE, The Netherlands.
authors.forename: Tjitske A
authors.initials: TA
authors.lastname: Boonstra
mesh_terms: D000293:Adolescent; D000328:Adult; D002908:Chronic Disease; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D007206:Individuality; D007866:Leg / Q000502:physiology* / Q000503:physiopathology; D008297:Male; D009044:Motor Cortex / Q000502:physiology* / Q000503:physiopathology; D020521:Stroke / Q000503:physiopathology*; D065908:Transcranial Direct Current Stimulation; D016138:Walking / Q000502:physiology*; D055815:Young Adult
keywords: Direct current stimulation; Lower extremities; Motor cortex; Stroke rehabilitation; Walking