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Mouth rinsing and ingestion of a bitter-tasting solution increases corticomotor excitability in male competitive cyclists

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Abstract

Purpose

Recently, we have shown that the combination of mouth rinsing and ingesting a bitter-tasting quinine solution immediately prior to the performance of a maximal 30-s cycling sprint significantly improves mean and peak power output. This ergogenic effect was proposed to be related to the activation of the corticomotor pathway by afferent taste signals originating from bitter taste receptors in the oral cavity. The aim of the present study was to use single-pulse transcranial magnetic stimulation to investigate whether mouth rinsing and ingestion of a bitter quinine solution increases corticomotor excitability.

Methods

A series of 10 motor-evoked potentials (MEPs) were recorded from the relaxed first dorsal interosseus muscle in 16 male competitive cyclists immediately before and after they rinsed their mouth for 10 s and then ingested either a 2 mM bitter quinine solution or plain water.

Results

Mean MEP amplitude was significantly increased in response to quinine administration by 16 % (p < 0.05), with no evidence of a time-dependent effect over the 10 pulses. Mean MEP amplitude also increased by 10 % in response to water administration (p < 0.05), though this increase was significantly smaller than the response to quinine (p < 0.05).

Conclusions

We conclude that the activation of bitter taste receptors in the oral cavity and upper gastrointestinal tract has the capacity to increase corticomotor excitability in male competitive cyclists.

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Abbreviations

ANOVA:

Analysis of variance

EMG:

Electromyographic

GI:

Gastrointestinal

FDI:

First dorsal interosseus

Hz:

Hertz

fMRI:

Functional magnetic resonance imaging

MEP:

Motor-evoked potential

rMT:

Resting motor threshold

PROP:

6-n-propylthiouracil

SNS:

Sympathetic nervous system

TMS:

Transcranial magnetic stimulation

\({\dot{V}}\)O2peak :

Peak oxygen uptake

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Authors and Affiliations

  1. School of Sport Science, Exercise and Health, The University of Western Australia, 35 Stirling Highway, Crawley, WA, 6009, Australia

    Sharon Gam, Kym J. Guelfi & Paul A. Fournier

  2. School of Psychology, The University of Western Australia, Crawley, Australia

    Geoff Hammond

Authors
  1. Sharon Gam
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  2. Kym J. Guelfi
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  3. Geoff Hammond
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  4. Paul A. Fournier
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Corresponding author

Correspondence to Sharon Gam.

Additional information

Communicated by Michael Lindinger.

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Gam, S., Guelfi, K.J., Hammond, G. et al. Mouth rinsing and ingestion of a bitter-tasting solution increases corticomotor excitability in male competitive cyclists. Eur J Appl Physiol 115, 2199–2204 (2015). https://doi.org/10.1007/s00421-015-3200-2

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  • DOI: https://doi.org/10.1007/s00421-015-3200-2

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