Minty mouthwash: the coolest way to perform in the heat?

Up to date research

During the last six years or so, the interest in menthol for enhancing hot-weather exercise performance has continued, albeit with mixed results; while nearly all studies have found improvements in thermal sensations, not all studies have reported actual performance benefits. In 2023 for example, one study reported that peppermint oil (containing menthol) improved the time to exhaustion in recreational runners performing in the heat⁽⁷⁾.

In that same year however, another study on trained runners - this time consuming menthol-containing gels – found no improvements in self-paced 20-minute time trial performance compared to a flavor-matched placebo⁽⁸⁾. Meanwhile, a 2024 systematic review and meta-study of menthol use (where data from a range of previous menthol studies was pooled and reanalyzed) found no improvement overall in exercise capacity or performance compared to placebo across a range of sports⁽⁹⁾. Interestingly however, when focusing purely on endurance sports, there did seem to be a performance benefit.

Coming right up to date, a systematic and meta-review study last year looked at the effects of nutritional supplements on endurance performance and subjective perception in a total of 552 endurance and team-sport athletes across a range of abilities when exercising in the heat⁽¹⁰⁾. It concluded the following:

·        Menthol (and taurine) showed positive effects in improving subjective thermal comfort and endurance performance.

·        Among all interventions, menthol energy gels demonstrated the most robust potential for reducing thermal sensations of heat stress.

·        When ranking the supplements against each other for hot-weather performance benefits, menthol stood out as being the most likely nutrient to deliver significant benefits (see figure 1).

Meanwhile, another 2025 study investigated the use of menthol mouthwashes for hot-weather (35C/95F) performance, particularly what was the optimal dosing⁽¹¹⁾. It found that a dose/concentration of between 0.01% and 0.10% was optimal for improving hot-weather performance (by about 6%). This is interesting as optimal menthol dosing, and frequency of use have not been established, which might explain the varied result from previous studies.

Figure 1: Ranking of nutrient effectiveness (using ‘P-scores’) in hot weather

Menthol’s P-score of 98% means that, on average, it outperformed 98% of the competing interventions (including placebo or no intervention) in this comparison. A score this high (approaching 100%) suggests that menthol use is the best strategy for enhancing hot-weather performance and/or reducing thermal sensations.

New research

Just in time for summer, a new study on menthol use for endurance athletes (in this case cyclists) has just dropped⁽¹²⁾. Published one month ago in the journal ‘Nutrients’, this study set out to investigate if and how menthol mouthwash could improve hot-weather, high-intensity cycling performance in young cyclists, but also to try and understand exactly how any benefits occur by studying muscle activation patterns in these cyclists (ie the effect of menthol on the ‘neural drive’ system). The participants were relatively young (average age 16.7 years), and were intentionally chosen because to date there’s been little data about menthol use gathered from young cyclists.

The study was conducted in controlled laboratory conditions with environmental conditions maintained at 31.5C/89F and 23.4% humidity. After a familiarization session to ensure the cyclists knew what to expect, all the cyclists conducted two separate cycling trials on two separate occasions (a week apart) in a randomized order. These cycling trials were identical and consisted of a ‘Modified Variable Cycling Test’ (M-VCT) – see box 1.

The M-VCT cycling test

The M-VCT is a cycling performance testing protocol designed to mimic the unpredictable and varying nature of real-world cycling (ie a where a mixture of hill efforts, sprint attacks, and even pacing is needed) rather than the steady-state tests often used in lab studies, and where cyclists have to hold a constant power or increase it linearly. Data obtained from this test is far more representative of real performance on the road than pure lab testing. The test itself lasts 30 minutes and consists of 6-minute ‘laps’ repeated five times. Within each lap, the cyclist is asked to perform a specific sequence of efforts:

·        Low-intensity steady-state riding.

·        Short accelerations – measured in 6-second bursts of very high-intensity effort).

·        Maximal power sprints (10-second maximum power output).

Taken as a whole, this test measures a cyclist’s ability to handle constantly changing power demands. Importantly, the test-retest accuracy is very high – within 0.46% - which makes it an excellent testing protocol when comparing an intervention (in this case menthol use) and a placebo condition in different trials.

The experimental procedure

In the two (identical) cycling trials above, the only difference to the protocol was what the cyclists used as a mouthwash:

·        In the intervention trial, the cyclists performed a mouth rinse for approximately 5–10 seconds every six minutes using a 0.01% menthol solution.

·        In the placebo trial, the cyclists performed a mouth rinse for approximately 5–10 seconds every six minutes using a berry-flavored, sucralose-sweetened solution matched for color and temperature.

During these two trials, the researchers took a number of measurements relating to performance and to try and better understand the physiological mechanisms behind and menthol mouth rinsing benefits. To do this, the cyclists’ power outputs and cadences (RPM) were constantly recorded. In addition, their perceptions of effort/fatigue and their affective feelings (how much they were enjoying or not enjoying the task!) were recorded after every mouth rinse. A key part of the study was to also track the cyclists’ neuromuscular activity. This was done by measuring muscle electrical activity in five key leg muscles: the vastus lateralis of the outer thigh, the vastus medialis of the inner frontal thigh, the rectus femoris of the mid frontal thigh, the tibialis anterior of the shin and the medial gastrocnemius of the mid calf.

What they discovered

When the cyclists used menthol mouth rinsing, they performed significantly better at various time points of the M-VCT test (see figure 2). Most noteworthy was the superior performance during lap #3 when both average power and 10-second maximal power were significantly increased, and the 6-second acceleration during laps #3 and #4, which also significantly increased. In fact, all three parameters trended towards better performance during all six laps, but due to the relative small number of participants, the gains weren’t quite large enough to meet the strict significance test (a repeat study with larger numbers of cyclists would likely show significant gains across all laps in all performance measures).

Figure 2: Menthol vs. placebo and performance

Top left: mean power output was significantly greater in the menthol trial during lap #3 when compared to placebo. Top right: power output during 6-second acceleration was significantly greater in the menthol condition during laps #3 and #4. Bottom: maximal power output during the 10-second effort was significantly greater in the menthol condition during lap #3. NB: * denotes significant difference.

The second finding was that (surprisingly), despite the clear performance gains arising from menthol use, there were no significant differences in the participants’ perceived fatigue or their affective feelings towards the task. In short, using a menthol mouthwash allowed the cyclists to work harder without raising their perceived effort levels or negatively affecting their mood/emotional state, indicating an effective decoupling of the extra physical work from the psychological perception of that extra work.

Thirdly, and importantly for understanding how menthol might help performance, the measurement of neuromuscular activation in terms of muscle electrical activity revealed something very interesting; as the laps ticked by in the placebo trial, the activation in the leg muscles tended to very slightly decrease (as would be expected due to increasing fatigue). When the menthol mouthwash was used, this decrease also occurred at a slighter larger (but not significantly larger) rate. But, this was not the case for the most powerful ‘cycling muscle’ vastus lateralis. Here, the decrease was significantly larger (see figure 3). A similar trend (although not quite reaching significance) was noted for rectus femoris, which is also a key cycling muscle. This pattern of lower muscle activation in these key quadriceps muscles while maintaining higher power output with menthol mouthwashing suggests that menthol may work by improving neuromuscular efficiency – ie by modifying how the brain recruits motor units, allowing for more work with less neural cost as fatigue sets in.

Figure 3: Muscle activation of vastus lateralis in menthol vs. placebo trials

Take home advice for endurance athletes

This study provides further evidence that menthol when used as a mouthwash can improve endurance performance. What strengthens the findings is firstly that each cyclist undertook both the menthol and the placebo trial, meaning that they were able to serve as their own control (ie eliminating inter-individual variability). Secondly, the test used has a very high test-retest accuracy, which means that even though the performance gains were relatively modest, they were nevertheless very meaningful.

Although more research on the actual mechanisms are needed, the likely explanation is that by activating TRPM8 receptors in the mouth, the menthol mouth rinse sends a ‘cool’ signal to the brain, which may help override the normal inhibitory signals generated when exercising in a hot environment. The finding of reduced muscle electrical activity in the vastus lateralis (and to a lesser extent in rectus femoris) also indicates that this ‘cool’ signal could help shift the brain’s motor unit recruitment strategies – for example, allowing for a more efficient pedal stroke.

If you are an endurance athlete facing a competition in hot-weather conditions, should you consider using a menthol mouthwash? While not all studies are in unanimous agreement about the performance benefits of menthol, the evidence for menthol on balance is certainly favorable, especially where higher-intensity efforts are required. Indeed, the evidence strongly suggests that using menthol is one of the very best weapons at your disposal for combating thermal stress and improving performance. And even if some studies have found no definitive evidence that performance is enhanced, virtually all studies have shown that menthol use significantly improves thermal comfort in the heat – and what’s not to like about that?

In terms of actual usage, the evidence we’ve reviewed here suggests your best bet is to either use menthol-containing gels or a menthol mouthwash. If you use a mouthwash strategy as in the study above, note that good results were achieved by swilling with a menthol rinse every six minutes. This suggests that more frequent but small sensory interventions may be more effective than a single large dose. In a race setting, this could mean using a menthol rinse at every aid station. It’s important also to note that the ideal concentration of menthol is from 0.01% (1 gram of menthol crystals per liter of fluid) up to a maximum of 0.10%. Your best bet is to stick at the lower limit (as in the study above) as a menthol solution can create burning sensations if it’s too strong. For those who consume gels throughout a race, your best option might be simply to switch to a menthol-containing gel, which delivers both cooling sensations and energy.

If you want to test out menthol rinses or gels in training first (a good idea), note that you might not experienced reduced sensations of fatigue or any kind of ‘feel good’ factor. But where it should show is in your power output or speed during more intense efforts. A good idea therefore is to use a power meter or speedo to monitor any performance gains as your ‘internal monitoring system’ is unlikely to tell you that you’re going faster or harder. Remember too that the benefits of menthol are most likely to be observed during higher-intensity efforts, so this is where you should monitor your training performance most closely to see what gains you get.

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