Impact of Transcranial Direct Current Stimulation Intensity on Leg Muscle Fatigability in Healthy Adults

July 7, 2021 updated by: Craig D. Workman, PhD, University of Iowa

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.

Study Overview

Status

Completed

Conditions

Intervention / Treatment

Study Type

Interventional

Enrollment (Actual)

35

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • United States
    • Iowa
      • Iowa City, Iowa, United States, 52242
        • University of Iowa

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

18 years to 30 years (Adult)

Accepts Healthy Volunteers

No

Genders Eligible for Study

All

Description

Inclusion Criteria:

  1. Young adult (18-30 yrs)
  2. right-side dominant
  3. able to independently walk for 6 min
  4. at least 30 min of moderate-intensity, physical activity on at least 3 days of the week for at least the last 3 months
  5. without chronic neurological, psychiatric, or medical conditions
  6. not taking any psychoactive medications

Exclusion Criteria:

  1. pregnant
  2. known holes or fissures in the skull
  3. metallic objects or implanted devices in the skull (e.g., metal plate)
  4. current student of study personnel
  5. under the direct supervision of study personnel

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Crossover Assignment
  • Masking: Double

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Sham Comparator: Sham
Participants will have the anode (active electrode) placed over the brain area the controls their dominant leg and the cathode (return electrode) above the ipsilateral eyebrow. Stimulation is turned on (2 mA) for the 30 seconds at the beginning and the end of the trial, but stays at 0 mA in the intervening time.
Device: Sham transcranial direct current stimulation
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.
Other Names:
  • tDCS
Experimental: 2 mA
Participants will have the anode (active electrode) placed over the brain area the controls their dominant leg and the cathode (return electrode) above the ipsilateral eyebrow. Stimulation is ramped up to 2 mA over the first 30 seconds and stays at 2 mA for the remainder of the stimulation time.
Device: Transcranial direct current stimulation at 2 mA
Uses weak electrical current (2 mA intensity) to either increase or decrease brain excitability and improve functional or cognitive outcomes.
Experimental: 4 mA
Participants will have the anode (active electrode) placed over the brain area the controls their dominant leg and the cathode (return electrode) above the ipsilateral eyebrow. Stimulation is ramped up to 4 mA over the first 30 seconds and stays at 4 mA for the remainder of the stimulation time.
Device: Transcranial direct current stimulation at 4 mA
Uses weak electrical current (4 mA intensity) to either increase or decrease brain excitability and improve functional or cognitive outcomes.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Distance walked in the 6 Minute Walk Test
Time Frame: Through study completion, up to 6 months
Walk back and forth between two markers spaced 30 meters apart for six minutes
Through study completion, up to 6 months
Fatigue index from the isokinetic fatigue test
Time Frame: Through study completion, up to 6 months
Perform 40 consecutive flexion and extension repetitions of the knee on the dominant leg. After a 10 minute rest, do the same task on the the non-dominant leg.
Through study completion, up to 6 months

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

University of Iowa

Investigators

  • Principal Investigator: Craig D Workman, PhD, University of Iowa

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

May 1, 2019

Primary Completion (Actual)

June 24, 2019

Study Completion (Actual)

September 1, 2019

Study Registration Dates

First Submitted

March 23, 2020

First Submitted That Met QC Criteria

March 23, 2020

First Posted (Actual)

March 25, 2020

Study Record Updates

Last Update Posted (Actual)

July 8, 2021

Last Update Submitted That Met QC Criteria

July 7, 2021

Last Verified

July 1, 2021

More Information

Terms related to this study

Keywords

Other Study ID Numbers

  • 201902799

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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