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Determination of the optimal dose and dosing strategy for effective L-menthol oral rinsing during exercise in hot environments

Lookup NU author(s): Dr Owen JeffriesORCiD

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This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).

Abstract

© The Author(s) 2024. Purpose: This multi-study programme investigated the optimal concentration of l-menthol delivered as an oral mouth rinse to modulate thermo-behaviour during exercise in a hot environment (35 °C). Method: In study 1, 38 participants completed a survey to establish an effective and tolerable range of l-menthol concentration. 31 participants completed an RPE-protocol examining 1. the dose–response effect of l-menthol mouth rinse on exercise performance (n = 16) and 2. the temporal effectiveness of administering l-menthol in an incremental and decremental dosing pattern (n = 15). Power output, heart rate, body core temperature and thermal sensation were reported throughout. Results: The optimal menthol concentration for peak power was between 0.01 and 0.1% (~ 6% increase, P < 0.05) and 0.5% (~ 9% increase, P < 0.05) with respect to control. Work completed was increased at 0.01% (~ 5%, P < 0.05), at 0.1% (~ 3%, P < 0.05) and had a detrimental effect at 0.5% (− 10% decrease, P < 0.05). There were no differences between an ascending dose protocol (0.01 to 0.5%), descending dose protocol (0.5–0.01%) or a constant 0.01% dose protocol. There were no reported differences in body core temperature or heart rate across trials (P > 0.05). Conclusion: The optimal dose of l-menthol when delivered via oral rinsing is between 0.01 and 0.1%. At lower concentrations, l-menthol appears to be less effective and at higher concentrations (> 0.5%) l-menthol appears to elicit greater irritation and may not positively modulate thermo-behaviour during exercise in a hot environment.

Publication metadata

Author(s): Jeffries O, Jibi G, Clark J, Barwood M, Waldron M

Publication type: Article

Publication status: Published

Journal: European Journal of Applied Physiology

Year: 2025

Volume: 125

Pages: 629-638

Print publication date: 01/03/2025

Online publication date: 05/10/2024

Acceptance date: 04/09/2024

Date deposited: 15/10/2024

ISSN (print): 1439-6319

ISSN (electronic): 1439-6327

Publisher: Springer Nature

URL: https://doi.org/10.1007/s00421-024-05609-w

DOI: 10.1007/s00421-024-05609-w

Data Access Statement: The datasets generated during and/or analyzed during the current study are available from the corresponding author upon reasonable request.

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