Effect of tDCS on Sport Performance for Two Categories of Athletes : Explosive Profile and Enduring Profile

Effets de la tDCS Sur la Performance Sportive de 2 Profils d'athlètes : Explosifs (Sauteurs de Haut Niveau et Amateur) et Endurants (Cyclistes de Haut Niveau et Amateur)

The study aims to compare the effects of tDCS applied on the dorsolateral prefrontal cortex (dlPFC) vs sham on the neuromuscular system. Two types of athletes will benefit from stimulation: jumper and cyclists. Short and long term effects are assesed by electromyographic records, experimental tasks and self-rated scales.

Transcranial direct current stimulation is a technique of noninvasive brain stimulation which delivers a electrical current to the scalp to modulate the neuronal activity. Depending on the polarity of stimulation, tDCS induces a neural hyperexcitability (with anode) or hypoexcitability (with cathode) of the target area.

Due to its neuromodulatory action, ease of use and low safety, tDCS can be used as a potential treatment but also as an investigative tool in neurophysiology. Thus, studies have shown a beneficial effect of tDCS on cognitive and motor functions. Nevertheless, studies conducted on motor performance and the reduction of neuromuscular fatigue show disparate results. It is impossible to conclude whether tDCS allows for improved performance and is a means of doping.

With a prospective, sham-controlled, crossover, double-blind design, this study aims to evaluate the effect of tDCS on neuromuscular fatigue resistance during explosive (jumping) and endurance (cycling) exertion.

This study is divided into two parts:

• Part A: jumping group
• Part B: cycling group.

During Part A, participants visit the laboratory on 3 occasions. Each visit is organized in the same way and is at least 48 hours apart from the previous one.

Participants are divided into two groups according to their level of experience (amateurs vs. high level).

Before the session of tDCS, participants carry out a psychometric assessment (MCQ, BIS10) and experimental tasks (BART, EEFRT, STROOP test and Go NoGo task). Then, they performed three types of jumps (long jump, squat jump and countermovement jump). Finally, participants benefit from neuromuscular tests (EMG recording of plantar flexor muscle activity, percutaneous stimulation of the posterior tibial nerve).

Subjects will be submitted to three sessions of tDCS (2 actives and one sham), one by visit, in the order of randomization. Current intensity will be of 2 mA (or 0 mA), through 25 cm² surface electrodes, during 20 minutes. The positioning of the stimulation electrodes will be carried out in compliance with EEG 10/20 standards:

- Sequence order determined by randomization:

1. Anode: F3 / Cathode: AF8/ Stimulation intensity: 2 mA
2. Anode: F3/ Cathode: AF8/ Stimulation intensity: 0 mA
3. Anode: FC2/ Cathode: Left shoulder/ Stimulation intensity: 2 mA

Immediately after the stimulation, participants perform motor and cognitive task again and the results are compared.

During part B, subjects participate in two training sessions of five days each. The training sessions are one month apart.

Participants are divided into three groups according to their level of experience (amateurs vs. high level vs. sedentary).

Each day, the subjects perform two twenty-minute time trials during which they receive a session of tDCS. (one week with the active tDCS, one week with the sham). So, subjects will be submitted to 10 tDCS stimulation sessions (active or sham) for five consecutive days (2 sessions of 20 minutes/day). Current intensity will be of 2 mA, through 25 cm² surface electrodes, placed over the dlPFC and the supraorbital region (anode position over F3 and cathode over AF8, according to the EEG 10-20 international system).

At J1 and J5 of each session (before and after session training), subjects carry out a psychometric assessment (MCQ, BIS10) and experimental tasks (BART, EEFRT, STROOP test and Go NoGo task) and benefit from neuromusculars tests (EMG recording of plantar flexor muscle activity, percutaneous stimulation of the posterior tibial nerve). Baseline measures will be compared to those obtained immediately after the end of sessions (5 days: short-term effects), and to 12 and 30 days later (long-term effects). Active and sham stimulation sessions outcomes will as well be compared.

Inclusion Criteria:

• Man older than 18 years old

• Right-handed

• Signed informed Consent form

• Subject affiliated to or beneficing from a French social security regime

• According to groups :

  • Part A :

    • Group S1 : High level jump practice : more 4000 hours of practice during the last five years
    • Group S2 : Amateur jump practice : less 4000 hours of practice during the last five years

  • Part B :

    • Group C1 : High level cycling practice: more 4000 hours of practice during the last five years
    • Group C2 : Amateur cycling practice: less 4000 hours of practice during the last five years
    • Group T : Sedentary : less two hours of recreationally practice of sport by week

Exclusion Criteria:

• Younger than18 years old
• Left-handed
• Subject under measure of protection or guardianship of justice
• Subject beneficiary from a legal protection regime
• Subject unlikely to cooperate or low cooperation stated by investigator
• Subject not covered by social security
• Suject with comorbidities : addictive (except : tea, coffee, tobacco), psychiatric, severe somatic pathologies (specially tumors, degenerative disease) or progressive neurologic pathologie
• Subject being in the exclusion period of another study or provided for by the "National Volunteer File"