By Jason Koop,
Head Coach of CTS Ultrarunning
This year’s Summer Olympics was scheduled to be a hot one. Tokyo, already known for hot and humid summertime conditions, would have been (and probably will be) hotter than the previous three Olympic host cities (Kakamu et al. 2020). Athletes, coaches and sport scientists will do almost anything to combat the heat. And while the best heat acclimation strategies involve long term protocols such as saunas, hot water immersion baths and exercising in the anticipated environment, over the years more novel and creative strategies have emerged in an attempt to gain an edge. Some off these such as ice-cold drinks and pre-cooling ice vests have stood the test of time and are used routinely by athletes. Others have been tossed on the cutting room floor, either due to lack of efficacy, burdensome equipment and constraining logistics, or other challenges. I can distinctly remember two of these ill-fated attempts in the mid 2000’s in the form of an isopropyl alcohol rub (think of rubbing an alcohol pad on your skin) and a fancy negative pressure cooling glove pioneered by Stanford. Both had their merits, yet are rarely (if ever) seen actually used in practice.
This year’s attempt to combat the heat is taking the form of menthol rinses, sprays and lozenges. While we shouldn’t expect a Joe Camel endorsement anytime soon, the strategies are gaining enough traction that we will see more commercialized products in the near future. So, before the summer is over, should you back the truck up and load up on a case of Hall’s or try and find a pallet of Fisherman’s Friend on Amazon? Let’s dig into it.
How menthol works
Bite straight into a peppermint patty, a Hall’s cough drop or rub some Vicks on your skin and you will instantly recognize menthol’s power to alter your sensation of coolness. Menthol, found in peppermint and used in a wide range of other products, acts on your TRMP8 receptors, which are responsible detecting cold and cool temperatures (McKemy 2007) from the environment. Menthol (and other chemicals) has the ability to chemically trigger this cold sensing reaction, independent of your body being in a cool environment. Quite literally, your body ‘thinks’ it is cool, irrespective of your actual core temperature or you whether you are standing in the middle of Death Valley baking in the 120-degree sun.
Sensing your body is cooler than it actually is, you can run harder and farther (theoretically, at least) than you could otherwise in hot environments, as your internal protective mechanisms against overheating are at least temporarily chemically overridden. Your body is quite literally being tricked into thinking it is cooler than it actually is even though your core temperature and muscular temperature are unaltered or even elevated. The latter point is particularly salient. Your core temperature is not altered by menthol. It’s a trick in every sense of the word. This will be particularly important when considering the different contexts of where and when to use this strategy (more on that later).
Sports scientists and athletes eventually caught on to this idea and for decades have incorporated menthol rubs, sprays, drinks and mouth rinses to help athletes feel cooler in hot weather competitions. More recently, however, research has zeroed in on this area, attempting to illuminate the exact best protocols and practices for all types of athletes in different situations. Is an internal application (sports drink or mouth rinse) better than an external application (rub)? Does the effect work better for endurance activities or intermittent ones? What if you concocted a menthol ice slurry, potentially taking advantage of the literal and perceptual coolness at the same time?
Rising to the top of the heap, menthol mouth rinses has been the winner in both the research and practical realm, particularly for endurance athletes. That’s good news, as a simple mouth rise (almost like a commercial mouth wash) is easy to implement, relatively low cost and efficacious all at the same time. Both running performance and time to exhaustion tests have been shown to improve between 3% and 9% with menthol mouth rinses (Steven et al. 2016; Jeffries, Goldsmith and Waldron 2018, respectively). And, the effects are at least equal and perhaps greater when compared to ice slurry ingestion, and happen despite increases in core temperature (Stevens and Best 2016).
From a practical perspective, the mouth rinse can be delivered either pre workout (after a warm up) or in the middle of the workout for a cooling-induced performance boost. Now, I’m not advocating for everyone to start carrying around mouthwash in their hydration flask in lieu of your normal sports drink (although your dentist might approve of that plan) but the practical application of a menthol mouthwash might just be as simple. Warm up for your workout, swish around your menthol mouth rinse, spit, go run hard.
So where can you get it? To date, most of the use cases for menthol mouth swishing have been confined to the realms of elite sport. In those contexts, coaches and athletes have resorted to making their own rinses consisting of a ~.01%-.1% menthol solution by dissolving menthol crystals in alcohol and then adding to water (and sometimes even adding coloring to boot). Since I am guessing most of you reading this article are not chemists, your regular old Listerine contains .04% menthol (as well as a host of other ingredients), which is smack in the middle of this range.
Menthol sports drinks and gels are new to the market or nearing release, and the research for menthol ingestion recommends .01% – .05% solution for ingestion. On the other end of the spectrum, the lethal dose for menthol is estimated at 50–500 mg/kg of bodyweight (Gosselin 1984). While you can argue that water is toxic if you consume too much, the small potential benefit for ultraendurance athletes from ingesting menthol, the athlete tendency to believe that ‘if some is good, more is better’, and the possibility for ultrarunners to consume a lot of menthol because of the duration of our events, means menthol ingestion for ultrarunning may not be worth the effort.
If we’ve learned anything from the copious incorporation of cupping after the Rio Summer games (remember all those circular bruises on Michael Phelps?) or the proliferation of pickle juice stemming from the underdog Philadelphia Eagles guzzling the salty liquid then pummeling my beloved Dallas Cowboys during the hottest game in NFL history, my guess is that we will start seeing (more) commercialized menthol products in the form of mouth rinses rubs, gums and the like after the Tokyo 2021 games. There’s nothing that says ‘buy me’ quite like an elite athlete gargling and then spitting out an eerie green drink en route to gold.
However, the use of menthol mouth rinses (and other menthol applications) should be limited to situations where core temperature can be elevated for short amounts of time or when menthol can be used in conjunction with another core temperature reducing practices (like dumping ice on your head or in your hat). For example, I wouldn’t rely on a menthol mouth rinse to keep you (feeling) cool during the Western States 100, where you are exposed to high temperatures for many hours and core temperature needs to be managed throughout the race.
Menthol in sport is here and it’ll be here for the long haul. You might just see it at your next ultra when the temps turn up and athletes are looking to stay cool!
Gosselin, R.E., R.P. Smith, H.C. Hodge. Clinical Toxicology of Commercial Products. 5th ed. Baltimore: Williams and Wilkins, 1984., p. II-258
Jeffries O, Goldsmith M, Waldron M. L-Menthol mouth rinse or ice slurry ingestion during the latter stages of exercise in the heat provide a novel stimulus to enhance performance despite elevation in mean body temperature. Eur J Appl Physiol. 2018;118(11):2435-2442. doi:10.1007/s00421-018-3970-4
Kakamu T, Wada K, Smith DR, et al. Preventing heat illness in the anticipated hot climate of the Tokyo 2020 summer Olympic Games. Environ Health Prev Med 2017;22:68
McKemy DD. TRPM8: The Cold and Menthol Receptor. In: Liedtke WB, Heller S, editors. TRP Ion Channel Function in Sensory Transduction and Cellular Signaling Cascades. Boca Raton (FL): CRC Press/Taylor & Francis; 2007. Chapter 13. Available from: https://www.ncbi.nlm.nih.gov/books/NBK5238/
Stevens, C., Thoseby, B., Sculley, D., Callister, R., Taylor, L., & Dascombe, B. (2016). Running performance and thermal sensation in the heat are improved with menthol mouth rinse but not ice slurry ingestion. Scandinavian Journal of Medicine & Science in Sports, 26(10), 1209-1216.
Stevens, C., & Best, R. (2016). Menthol: A Fresh Ergogenic Aid for Athletic Performance. Sports Medicine, 47(6), 1035-1042.