Transcranial Direct Current Stimulation Improves the Cycling
Performance but Does Not Alter Neuromuscular Function
tDCS, Cycling Performance and Neuromuscular Function
Leandro Ricardo Altimari
1
, Marcelo Vitor-Costa
1
, Henrique Bortolotti
1
and Nilo Massaru Okuno
2
1
Group of Study and Research in Neuromuscular System and Exercise, Physical Education and Sport Center,
Londrina University State, Londrina, Paraná, Brazil
2
Department of Physical Education, Ponta Grossa University State, Ponta Grossa, Paraná, Brazil
1 OBJECTIVES
The main neurophysiologic mechanisms that
determine performance in physical activities or
sports are not well understood. This is mainly due to
the lack of technology that permits the study of the
human brain in vivo. In the last decades some
neuromodulation techniques have been developed
and, among them, the transcranial direct current
stimulation (tDCS) has been attracting attention as it
is easily applicable and permits to carry out well
controlled studies in humans, and has been shown to
be a strategy to enhance physical and mental
performance in sports (Davis, 2013).
Therefore, the objective of the present study was
to investigate the effects of anodic tDCS on the
physical performance and neuromuscular function in
cycling exercise.
2 METHODS
A total of 11 physically active subjects aged 26 ± 4
years, weighing 77 ± 15 kg and 177 ± 3 cm tall
participated in study. Initially all subjects performed
an incremental test in a cyclesimulator (model
Velotron DYNAFIT PRO™, RacerMate Inc., USA)
to determine the peak power (257 ± 35 W). In the
two subsequent visits to the laboratory the subjects
were randomly submitted to one of the two
stimulation conditions (Anodic tDCS or Placebo
tDCS) to verify their possible effect on a time to
exhaustion task at 80% of peak power (205 ± 28 W).
This study was approved by the local Institutional
Research Ethics Committee.
Stimulation was carried before each test during
13 min, with a current intensity of 2.0 mA. The time
between tDCS and the test was 10 min. Sessions
were separated by a minimal interval of 48h. We
used the 10-20 International System for EEG
electrode placement. The active electrode (9x4 cm)
was placed on the scalp having its center in the
region Cz 4.5 cm on each side of the head (purpose
of stimulating the motor cortex of both
hemispheres), and the reference electrode was
positioned over the bulge.
Additionally, the electromyographic (EMG)
signal of the muscle vastus lateralis (VL) was
monitored during tests after stimulation and
expressed in mean values of RMS - root mean
square (µV) and MF - median frequency (Hz) with a
5-second window period. For EMG signal
normalization a test for torque-speed [T–V test] was
used (Rouffet and Hautier, 2008).
For the recording the of EMG signal, was used
an electromyography model TeleMyo 2400TG2™
(NORAXON Inc., USA) and bipolar active EMG
electrodes (modelo TeleMyo 2400™, NORAXON
Inc., USA), with interelectrode distance fixed at 2
cm, which were placed in the right leg muscle and
fixed with a adhesive tape. Initially, a trichotomy
followed by asepsis with alcohol and curettage of
the electrode site, to reduce skin impedance, was
performed.
The localization of anatomical point for the
electrode placement on the analyzed muscle was
done according to the standardization proposed by
the Surface ElectroMyoGraphy for the Non-Invasive
Assessment of Muscles ISEK: International Society
of Electrophysiology and Kinesiology (SENIAM).
The sampling frequency of the EMG signals was
2.000 Hz. The signal passing limit was ±5 mV, and
the common-mode rejection ratio was 95 dB.
To obtain the values expressed in RMS, the raw
EMG signals were submitted to a band-pass digital
filter of 20 and 500 Hz and then rectified and
smoothed. The MF was determined using Fourier
analysis —‘‘Short-Time Fast Fourier Transform’’ —
and the signals were processed in the mathematical
simulation environment MatLab 7.0™ (Mathworks
Ricardo Altimari L., Vitor-Costa M., Bortolotti H. and Massaru Okuno N..
Transcranial Direct Current Stimulation Improves the Cycling Performance but Does Not Alter Neuromuscular Function - tDCS, Cycling Performance
and Neuromuscular Function.
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c
2013 SCITEPRESS (Science and Technology Publications, Lda.)