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

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.

Conditions

• Healthy

Interventions

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.

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.

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.

Sponsors & Collaborators

• University of Iowa

  lead OTHER

Principal Investigators

• Craig D Workman, PhD · University of Iowa

Study Design

Allocation

RANDOMIZED

Purpose

TREATMENT

Masking

DOUBLE

Model

CROSSOVER

Eligibility

Min Age

18 Years

Max Age

30 Years

Sex

ALL

Healthy Volunteers

Yes

Timeline & Regulatory

Start

2019-05-01

Primary Completion

2019-06-24

Completion

2019-09-01

Countries

• United States

Study Locations