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Oral l-menthol reduces thermal sensation, increases work-rate and extends time to exhaustion, in the heat at a fixed rating of perceived exertion



The study investigated the effect of a non-thermal cooling agent, l-menthol, on exercise at a fixed subjective rating of perceived exertion (RPE) in a hot environment.


Eight male participants completed two trials at an exercise intensity between ‘hard’ and ‘very hard’, equating to 16 on the RPE scale at ~35 °C. Participants were instructed to continually adjust their power output to maintain an RPE of 16 throughout the exercise trial, stopping once power output had fallen by 30%. In a randomized crossover design, either l-menthol or placebo mouthwash was administered prior to exercise and at 10 min intervals. Power output, \(\dot{V}\)O2, heart rate, core and skin temperature was monitored, alongside thermal sensation and thermal comfort. Isokinetic peak power sprints were conducted prior to and immediately after the fixed RPE trial.


Exercise time was greater (23:23 ± 3:36 vs. 21:44 ± 2:32 min; P = 0.049) and average power output increased (173 ± 24 vs. 167 ± 24 W; P = 0.044) in the l-menthol condition. Peak isokinetic sprint power declined from pre-post trial in the l-menthol l (9.0%; P = 0.015) but not in the placebo condition (3.4%; P = 0.275). Thermal sensation was lower in the l-menthol condition (P = 0.036), despite no changes in skin or core temperature (P > 0.05).


These results indicate that a non-thermal cooling mouth rinse lowered thermal sensation, resulting in an elevated work rate, which extended exercise time in the heat at a fixed RPE.

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Heart rate


Respiratory frequency


Rating of perceived exertion


TWIK-related arachidonic acid-stimulated K+ channel


TWIK-related K+-1 channel


Transient receptor potential cation channel subfamily M member 8


Minute ventilation

\(\dot{V}\)O2 :

Oxygen consumption


Tidal volume


Power output at \(\dot{V}\)O2max


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We would like to express our gratitude to the participants who took part in the experimental study.

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Correspondence to O. Jeffries.

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The authors declare that there is no conflict of interest.

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Communicated by Narihiko Kondo.

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Flood, T.R., Waldron, M. & Jeffries, O. Oral l-menthol reduces thermal sensation, increases work-rate and extends time to exhaustion, in the heat at a fixed rating of perceived exertion. Eur J Appl Physiol 117, 1501–1512 (2017).

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  • Menthol
  • Exercise
  • Heat
  • Thermoregulation
  • Perception
  • Pacing