ANODAL TRANSCRANIAL DIRECT CURRENT STIMULATION DOES NOT IMPROVE PERFORMANCE IN A TIME TRIAL CYCLING ERGOMETER TEST
Authors
Aaes, Jon Slettum ; Knudsen, Dennis
Term
4. semester
Education
Publication year
2018
Abstract
Anodal transkraniel jævnstrømsstimulation (a-tDCS) kan øge den kortikale excitabilitet i hjernen og er tidligere sat i forbindelse med længere tid til udmattelse samt ændringer i puls (HR) og oplevet anstrengelse (RPE) ved submaksimal træning. Denne undersøgelse skulle afklare, om 13 minutters a-tDCS forbedrer præstationen i en selvvalgt 250 kJ cykel-time trial og påvirker en 120 sekunders RPE-produktions-test med en målrettet subjektiv intensitet på 13 på RPE-skalaen. Tyve deltagere gennemførte begge tests fire gange i tilfældig rækkefølge (tilvænning, kontrol, sham og a-tDCS). Under 250 kJ time trial blev HR og VO2 målt, og RPE blev registreret for hver 25 kJ. I 11 af deltagerne blev motorisk fremkaldte potentialer (MEP) målt med transkraniel magnetisk stimulering (TMS) i sham- og a-tDCS-forløbene for at vurdere ændringer i kortikal excitabilitet. MEP steg signifikant efter 13 minutters a-tDCS (fra 452 ± 374 μV til 676 ± 642 μV; p = 0,038), hvilket tyder på øget kortikal excitabilitet. Der var ingen signifikante forskelle i gennemførselstid for 250 kJ time trial, i energiudbytte i RPE-produktions-testen, i RPE eller i VO2. En mindre forskel i puls blev observeret ved 200 kJ mellem kontrol (169 ± 12 bpm) og sham (172 ± 12 bpm). Samlet set ændrede a-tDCS ikke præstationen i den selvvalgte time trial. Konklusion: Selvom a-tDCS øgede MEP (et mål for hjernens excitabilitet), påvirkede 13 minutters stimulation ikke cykelpræstation, oplevet anstrengelse, puls eller iltoptagelse i denne protokol. Resultaterne tyder på, at 13 minutters a-tDCS ikke var tilstrækkeligt til at modulere de centrale mekanismer, der påvirker disse mål.
Anodal transcranial direct current stimulation (a-tDCS) can increase cortical excitability and has previously been linked to longer time to fatigue and changes in heart rate (HR) and perceived exertion (RPE) at submaximal intensities. This study tested whether 13 minutes of a-tDCS improves performance in a self-paced 250 kJ cycling time trial and affects a 120 s RPE-production test set to a perceived intensity of 13 on the RPE scale. Twenty participants completed both tests four times in randomized order (familiarization, control, sham, and a-tDCS). During the 250 kJ time trial, HR and VO2 were measured and RPE was recorded every 25 kJ. In 11 participants, motor evoked potentials (MEP) were assessed using transcranial magnetic stimulation (TMS) during the sham and a-tDCS sessions to evaluate changes in cortical excitability. MEP increased significantly after 13 minutes of a-tDCS (from 452 ± 374 μV to 676 ± 642 μV; p = 0.038), indicating higher cortical excitability. There were no significant differences in the completion time of the 250 kJ time trial, in energy output during the RPE-production test, in RPE, or in VO2. A small heart-rate difference was observed at 200 kJ between the control (169 ± 12 bpm) and sham (172 ± 12 bpm) conditions. Overall, a-tDCS did not change performance in the self-paced time trial. Conclusion: Although a-tDCS increased MEP (a marker of brain excitability), 13 minutes of stimulation did not alter cycling performance, perceived exertion, heart rate, or oxygen uptake in this protocol. These findings suggest that 13 minutes of a-tDCS was insufficient to modulate the central mechanisms underlying these outcomes.
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