4 mA tDCS, Estrogen, and Leg Muscle Fatigability

NCT ID: NCT04471805

Last Updated: 2023-05-10

Basic Information

• Recruitment Status: COMPLETED
• Clinical Phase: NA
• Total Enrollment: 10 participants
• Study Classification: INTERVENTIONAL
• Study Start Date: 2020-10-01
• Study Completion Date: 2021-11-01

Brief Summary

The majority of transcranial direct current stimulation (tDCS) studies have failed to consider sex as a modulating factor. This neglect may partly account for the high inter-subject variability bemoaned by many tDCS investigators (e.g., approximately 50% of participants do not respond to tDCS) and has certainly delayed progress in the field. Therefore, research into how sex influences stimulation-related outcomes is vital to fully understand the underlying mechanisms of tDCS, which has shown great inconsistency.

Because of the menstrual cycle, the hormonal levels of women fluctuate considerably more than in men. Importantly, these hormonal variations might impact the efficacy of neuromodulatory tools, like tDCS. It is suggested that estrogen, which is high in the second follicular phase, reinforces excitatory mechanisms in the motor cortex. However, because anodal tDCS enhances cortical excitation there is also a possibility of excessive excitability. For instance, anodal tDCS may lead to overexcitation and non-optimal performance when it is applied in the second follicular phase of the menstrual cycle. Currently, there is a lack of knowledge on how the phases of the menstrual cycle affect tDCS performance outcomes in healthy young women because no studies have examined if and how the phases of the menstrual cycle alter tDCS efficacy.

This study is critical for determining the optimal time to administer anodal tDCS, and the ideal intensity for that administration, to achieve the most beneficial results. Furthermore, this investigation will emphasize the need for future tDCS studies to test women during the same menstrual cycle phase.

Detailed Description

The majority of transcranial direct current stimulation (tDCS) studies have failed to consider sex as a modulating factor. This neglect may partly account for the high inter-subject variability bemoaned by many tDCS investigators (e.g., approximately 50% of participants do not respond to tDCS) and has certainly delayed progress in the field. Therefore, research into how sex influences stimulation-related outcomes is vital to fully understand the underlying mechanisms of tDCS, which has shown great inconsistency.

Because of the menstrual cycle, the hormonal levels of women fluctuate considerably more than in men. There are two main phases of the menstrual cycle: 1) the follicular phase, characterized by low levels of estradiol and progesterone (first follicular phase, days 1-7) followed by increased levels of estradiol and low levels of progesterone (second follicular phase, days 7-14); and 2) the luteal phase (days 14-28), characterized by moderate estradiol and high progesterone levels. Importantly, these hormonal variations might impact the efficacy of neuromodulatory tools, like tDCS.

It is suggested that estrogen, which is high in the second follicular phase, reinforces excitatory mechanisms in the motor cortex. Thus, it appears that higher levels of estradiol increase cortical excitability. However, because anodal tDCS enhances cortical excitation there is also a possibility of excessive excitability. For instance, anodal tDCS may lead to overexcitation and nonoptimal performance when it is applied in the second follicular phase of the menstrual cycle. Currently, there is a lack of knowledge on how the phases of the menstrual cycle affect tDCS performance outcomes in healthy young women because no studies have examined if and how the phases of the menstrual cycle alter tDCS efficacy.

This research will be significant because the changing hormone levels during the different phases of menstruation in women is an especially important factor for minimizing response variability from tDCS. Thus, this study is critical for determining the optimal time to administer anodal tDCS, and the ideal intensity for that administration, to achieve the most beneficial results. Furthermore, this investigation will emphasize the need for future tDCS studies to test women during the same menstrual cycle phase.

Conditions

Healthy

Study Design

• Allocation Method: NA
• Intervention Model: SINGLE_GROUP
• Primary Study Purpose: TREATMENT
• Blinding Strategy: NONE

Study Groups

Eumenorrheic Women

Participants will have the anode (active electrode) placed over the brain area that controls their dominant leg and the cathode (return electrode) above the ipsilateral eyebrow. tDCS is administered in the early follicular phase, late follicular phase, and mid-luteal phase of their menstrual cycle.

tDCS: Stimulation is ramped up to 4 mA over the first 30 seconds and stays at 4 mA for the remainder of the simulation time.

Sham: Stimulation is turned on (4 mA) for 30 seconds at the beginning and the end of the trial but stays at 0 mA in the intervening time.

Group Type: EXPERIMENTAL

Sham transcranial direct current stimulation 4 mA

Intervention Type: DEVICE

Uses weak electrical current (4 mA intensity) at the beginning and the end of a given stimulation period to control for potential placebo-like effects or participant expectation bias.

Transcranial direct current stimulation 4 mA

Intervention Type: DEVICE

Uses weak electrical current (4 mA intensity) to either increase or decrease brain excitability and improve functional or cognitive outcomes.

Interventions

Sham transcranial direct current stimulation 4 mA

Uses weak electrical current (4 mA intensity) at the beginning and the end of a given stimulation period to control for potential placebo-like effects or participant expectation bias.

Intervention Type: DEVICE

Transcranial direct current stimulation 4 mA

Uses weak electrical current (4 mA intensity) to either increase or decrease brain excitability and improve functional or cognitive outcomes.

Intervention Type: DEVICE

Other Intervention Names

Sham tDCS 2 mA; tDCS 4 mA

Eligibility Criteria

Inclusion Criteria

1. Has a regular menstrual cycle

2. Young adult (18-35 years)

3. Right-side dominant

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. Women on hormonal contraceptives/supplements.

• Minimum Eligible Age: 18 Years
• Maximum Eligible Age: 35 Years
• Eligible Sex: FEMALE
• Accepts Healthy Volunteers: Yes

Sponsors

University of Iowa

OTHER

Sponsor Role: lead

Responsible Party

Thorsten Rudroff

Assistant Professor

Responsibility Role: PRINCIPAL_INVESTIGATOR

Principal Investigators

Thorsten Rudroff, PhD

Role: PRINCIPAL_INVESTIGATOR

Health and Human Physiology

Locations

University of Iowa

Iowa City, Iowa, United States

Countries

United States

Provided Documents

Document Type: Study Protocol and Statistical Analysis Plan

View Document

Other Identifiers

202005124

Identifier Type: -

Identifier Source: org_study_id