Impact of Transcranial Direct Current Stimulation Intensity on Leg Muscle Fatigability in Healthy Adults
Condition: Healthy
Study type: Interventional

Summary: 
      Transcranial direct current stimulation (tDCS) is a painless,non-invasive means of increasing
      brain excitability. It has been used for several years and in many populations to improve
      physical and psychological outcomes. Although many tDCS devices are capable of a range of
      stimulation intensities (e.g., 0 mA - 5 mA), the intensities currently employed in most tDCS
      research are ≤ 2 mA, which are sufficient to elicit measurable improvements; but, these
      improvements might be expanded at higher intensities. In the beginning, when the safety of
      tDCS was still being established for human subjects, careful and moderate approaches to
      stimulation protocols were warranted. However, recent work using stimulation at higher
      intensities, i.e. up to 4 mA, has been performed in many populations and was found to have no
      additional negative side-effects. Now that the safety of tDCS at higher intensities is better
      established, work exploring the differences in performance between moderate (i.e. 2 mA) and
      higher (i.e. 4 mA) intensities is necessary to determine if increasing intensity increases
      the effectiveness of the desired outcome.

      Prospective participants will include 40 healthy young adults (all right-side dominant) that
      will be recruited to complete four randomly ordered stimulation sessions (Baseline, 2 mA, 4
      mA, and sham), separated by at least 5 days. Each session will involve one visit to the
      Integrative Neurophysiology Laboratory (INPL) and will last for approximately one hour. We
      expect data collection to last 6 months. The first session includes leg strength measurements
      and fatigue tasks of both legs, as well as a baseline 6 min walk test (6MWT) to determine
      fatigued walking characteristics. The following three sessions will include performing a
      random tDCS condition (2 mA, 4 mA, or sham) over the brain area that controls the
      participant's dominant leg for 15 minutes prior to and then throughout the duration of the
      fatigue task of the dominant leg (16-20 min total stimulation time). The fatigue task for the
      nondominant leg will be performed after a 10 minute energy recovery period. After the fatigue
      task has been completed for both legs, the participants will perform the 6MWT.
    


Intervention name(s): Sham transcranial direct current stimulation; Transcranial direct current stimulation at 2 mA; Transcranial direct current stimulation at 4 mA
Intervention type(s): Device; Device; Device
Intervention description(s): Uses weak electrical current (2 mA intensity) at the beginning and the end of a given stimulation period to control for potential placebo-like effects or participant expectation bias.; Uses weak electrical current (2 mA intensity) to either increase or decrease brain excitability and improve functional or cognitive outcomes.; Uses weak electrical current (4 mA intensity) to either increase or decrease brain excitability and improve functional or cognitive outcomes.
Other intervention name(s): tDCS
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: Double (Participant, Investigator)
Primary purpose: Treatment
Keywords: Brain Stimulation