The Effects of Cathodal tDCS on Muscle Strength in Healthy Adults

To investigate the effects of different intensity of cathodal tDCS on muscle strength in healthy adults.

Study Overview

• Status: Completed
• Conditions: Healthy Participants
• Intervention / Treatment: Device: Transcranial direct current stimulation

Detailed Description

Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique that can modulate cortical excitability. In 2000, Nitsche and Paulus reported the polarity-dependent effect of tDCS in humans, i.e., anodal tDCS facilitates cortical excitability while cathodal tDCS decreases it. (Nitsche & Paulus, 2000). TDCS studies have been replicated by many researchers and reported similar effects of tDCS in humans when using anodal and cathodal tDCS with an intensity of 1 mA. The linear effect of tDCS also has been reported by various studies, i.e., when increase intensity, the polarity-dependent effect of tDCS also enhances. However, conflicting results of cathodal tDCS efficacy have been reported.

Cortical excitability has been used to represent the efficacy of tDCS on neuroplasticity. The linear effect of cathodal tDCS on cortical excitability have been reported by researchers when using intensities at 1, 2, and 3 mA stimulated at the primary motor cortex in healthy participants (Batsikadze et al., 2013; Jamil et al., 2017; Kuo et al., 2013; Mosayebi Samani et al., 2019; Nitsche et al., 2003). Nevertheless, some studies showed the non-linear effects of cathodal tDCS (i.e., when increases intensity, cathodal tDCS enhances the cortical excitability) when using intensities at 1.5 and 2 mA in healthy participants (Batsikadze et al., 2013; Jamil et al., 2017; Mosayebi Samani et al., 2019). Hence, cathodal tDCS efficacy on cortical excitability is still controversy.

Muscle performance is an outcome that represents clinical change induced by tDCS. Previous studies reported the tendency of cathodal tDCS efficacy in decreasing muscle performance of both upper and lower extremities in healthy participants (Cogiamanian et al., 2007; Tanaka et al., 2009). However, previous studies used a single intensity of tDCS in each study. Hence, there was no direct comparison between different intensities of cathodal tDCS on muscle performance in healthy participants.

In our study, we aim to investigate the effect of different intensities of cathodal tDCS on muscle strength in healthy participants.

• Study Type: Interventional
• Enrollment (Actual): 48
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Thailand
  • Nakhon Pathom
    • Salaya, Nakhon Pathom, Thailand, 73170
      • Faculty of Physical Therapy, Mahidol University

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 60 years (Adult)
• Accepts Healthy Volunteers: Yes
• Genders Eligible for Study: All

Description

Inclusion Criteria:

1. Male and female healthy adults
2. Age range between 18 - 60 years old
3. Right-handed dominant identified by the Edinburg Handedness Inventory
4. No recent muscle injuries of both limbs for a past 6-months

Exclusion Criteria:

1. Consumed caffeine within 24 hours prior the experiment
2. History of neurological symptoms i.e. seizures, weakness, loss of sensation or unclear history of pass illness
3. Presence of metal implantation, intracranial shunt, cochlear implantation or cardiac pacemakers
4. Presence of opened wound or infectious wound around scalp
5. Presence of pain in evaluating muscle groups
6. History of surgery in evaluating limbs

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Other
• Allocation: Randomized
• Interventional Model: Factorial Assignment
• Masking: Double

Number of Arms

4

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Sham Comparator: Sham tDCS; Sham transcranial direct current stimulation (tDCS) will be applied for 20 mins. Cathode on the primary motor area (M1) and Anode on the supraorbital area of contralateral side. Current intensity will be at 2 mA (sham mode). The scope of intervention is to investigate effect of sham tDCS on muscle strength.	Device: Transcranial direct current stimulation; Cathodal tDCS will be applied for 20 mins.
Experimental: Cathodal-tDCS 1 mA; Cathodal transcranial direct current stimulation (tDCS) will be applied for 20 mins. Cathode on the primary motor area (M1) and Anode on the supraorbital area of contralateral side. Current intensity is fixed at 1 mA and current will flow continuously. The scope of intervention is to investigate effect of cathodal tDCS on muscle strength.	Device: Transcranial direct current stimulation; Cathodal tDCS will be applied for 20 mins.
Experimental: Cathodal-tDCS 1.5 mA; Cathodal transcranial direct current stimulation (tDCS) will be applied for 20 mins. Cathode on the primary motor area (M1) and Anode on the supraorbital area of contralateral side. Current intensity is fixed at 1.5 mA and current will flow continuously. The scope of intervention is to investigate effect of cathodal tDCS on muscle strength.	Device: Transcranial direct current stimulation; Cathodal tDCS will be applied for 20 mins.
Experimental: Cathodal-tDCS 2 mA; Cathodal transcranial direct current stimulation (tDCS) will be applied for 20 mins. Cathode on the primary motor area (M1) and Anode on the supraorbital area of contralateral side. Current intensity is fixed at 2 mA and current will flow continuously. The scope of intervention is to investigate effect of cathodal tDCS on muscle strength.	Device: Transcranial direct current stimulation; Cathodal tDCS will be applied for 20 mins.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change from baseline muscle strength after tDCS	Muscle strength will be measured in Newton by using a hand-held dynamometer.	Baseline (Pretest) and 40 minutes ( posttest)

Collaborators and Investigators

• Sponsor: Mahidol University

Study record dates

Study Major Dates

• Study Start (Actual): November 16, 2020
• Primary Completion (Actual): March 31, 2022
• Study Completion (Actual): March 31, 2022

Study Registration Dates

• First Submitted: December 9, 2020
• First Submitted That Met QC Criteria: December 16, 2020
• First Posted (Actual): December 17, 2020

Study Record Updates

• Last Update Posted (Actual): June 22, 2022
• Last Update Submitted That Met QC Criteria: June 19, 2022
• Last Verified: June 1, 2022

More Information

Terms related to this study

• Other Study ID Numbers: MU-CIRB2020/314.0210

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No