Nachwuchsworkshop der Arbeitsgemeinschaft für die Sportpsychologie

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Uri Borges - Participant

Transcutaneous vagus nerve stimulation: The effect of different stimulus intensities on cardiac vagal activity

Transcutaneous Vagus Nerve Stimulation (tVNS) is a technology used to electrically and non-invasively modulate the vagal activity. Given the importance of the vagus nerve, which is involved in physiological, cognitive, as well as in emotional regulatory processes (Thayer, Hansen, Saus-Rose & Johnsen, 2009), this stimulation method has recently been receiving increasing attention. tVNS can contribute to a better understanding of cognitive functions, for instance working memory, as well as of emotion regulation processes, two central research topics in sport psychology. However, the lack of knowledge on stimulation parameters with regards to the efficacy of tVNS may represent an important limitation of this method (Burger et al., 2016). The present study aims at identifying the best stimulation intensity to optimize cardiac vagal activity (CVA) by taking into account the physiological effect of tVNS, using vagally mediated heart rate variability indicators (p.ex. root mean square of successive differences between normal heartbeats, RMSSD), as well as the subjective stimulation perception. Three experiments (within-subject designs, on average 68 healthy participants, mainly sport students, 25 female subjects, 23.2 years), have been carried out. In Experiment 1, we applied the set stimulation method, comparing three different predetermined stimulation intensities. In Experiment 2, we compared the set stimulation method with the free stimulation method, in which the participants were instructed to freely choose an intensity. In Experiment 3 we compared both methods with their respective sham stimulations. In Experiment 1, CVA increased during stimulation in comparison to the resting measures, F(2, 120) = 130.673, p < .001, η² = .685, but no differences could be found between the different stimulations. Furthermore, subjects rated the tVNS as more unpleasant, the stronger it was, F(4, 236) = 2.520, p = .042, η² = .041. In Experiment 2, a similar result could be observed regarding CVA when comparing both stimulation methods, but the set stimulation method was rated as more unpleasant than the free stimulation method, t(76) = 3.247, p = .002, d = .451. Results of Experiment 3 will be presented at the conference. In summary, neither different stimulation intensities nor different methods to determine the stimulation intensity seem to stimulate the cardiac vagus nerve to different extents, but the free stimulation method was perceived as more pleasant. Thus, this method may be the best way to determine stimulation intensity. These results may contribute to a better application of tVNS in research and practice.
Nachwuchsworkshop der Arbeitsgemeinschaft für die Sportpsychologie

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