Athlete perceptions of flavored, menthol-enhanced energy gels ingested prior to endurance exercise in the heat

Abstract

Background L-menthol evokes a cooling sensation by activating cold sensing cation channels. Menthol-enhanced fluids can be ergogenic during exercise in the heat by improving thermal perception; hence, the addition of menthol to energy gels may benefit athletes. Previously, unflavored menthol gels were deemed acceptable at 0.1% concentration, but no research has been undertaken on menthol gels with additional flavoring. Therefore, we determined athlete perceptions of flavored energy gels with different menthol concentrations. Methods With a randomized, crossover, double-blind, placebo-controlled design, 27 athletes (34.8 ± 6.7 y, 9 females) ingested an energy gel with either 0.1%, 0.3%, 0.5%, or 0.7% menthol concentration, or a non-menthol, flavor-matched placebo (CON), on separate occasions before outdoor exercise. Gels were rated for cooling sensation, irritation, flavor, and overall experience on 100-point sensory and hedonic labeled magnitude scales. The duration of any cooling sensation was also reported. Results All menthol gels delivered a greater cooling sensation compared to CON (7.4 ± 8.1 AU) with a significantly greater response for 0.7% (59.9 ± 20.5 AU) and 0.5% (57.7 ± 21.8 AU), compared to all others. Irritation was higher for all menthol gels compared to CON (3.4 ± 7.2 AU) and for 0.7% compared to 0.1% (31.1 ± 31.0 vs. 16.3 ± 21.0 AU, p = 0.041), with none rated above a ‘mild-moderate’ intensity. The menthol gels delivered a significantly longer cooling sensation duration (12.3-19.6 min) versus CON (2.2 ± 4.8 min) with no difference between menthol gels. Conclusion A flavored menthol energy gel at 0.1–0.7% concentration provides a cooling sensation for athletes when ingested before exercise. The 0.5% concentration is recommended to maximize the cooling sensation whilst minimizing irritation.

A Menthol-Enhanced “Cooling” Energy Gel Does Not Influence Laboratory Time Trial Performance in Trained Runners

“…The perceptual cooling effect of menthol during use in sport has been observed at lower concentrations (i.e., 0.01-0.1% menthol) by previous investigators [16][17][18][19]. The menthol gels in the current study, by contrast, contained a higher concentration (0.5% menthol) and have been demonstrated to impart a cooling sensation lasting up to 20 min when ingested prior to running in warm outdoor conditions (27.5 ± 6.8 • C, 58.2 ± 23.2% RH) [24]. The environmental conditions in the current study were hotter (i.e., 33 • C, 49% RH), and it is possible that the thermal stress that was produced (see Figure 2b) was too high, thereby outweighing any menthol sensory cooling that would notably impact perceptual measures.…”

“…Energy gels with a 0.5% menthol concentration, as determined from and described in a previous investigation [24], were produced by a commercial sports nutrition manufacturer (GU Energy Labs, Berkeley, CA, USA) using the following ingredients: maltodextrin, water, fructose, L-leucine, sodium citrate, medium-chain triglycerides, sea salt, potassium citrate, citric acid, calcium carbonate, L-valine, gellan gum, L-isoleucine, sodium benzoate (preservative), potassium sorbate (preservative), natural L-menthol (Sigma-Aldrich, St. Louis, MO, USA), and natural citrus flavor. A placebo gel was also produced containing a natural mint flavor in place of the l-menthol (Virginia Dare, Brooklyn, NY, USA), as previously described [23].…”

“…Previously, we have developed, optimized, and demonstrated that a menthol-enhanced energy gel at a 0.5% concentration imparts a perceptual cooling sensation lasting up to 20 min during exercise in warm/humid outdoor conditions [23,24]. The optimized gel, which produced a significantly greater cooling sensation than lower-concentration menthol gels (e.g., 0.1% and 0.3%) without causing irritation, was an improvement on a previous version which had been deemed "too strong" in flavor and therefore unacceptable to athletes [23].…”

No effect of a commercial carbohydrate‐menthol drink on thermal perceptual measures or 15‐min time trial performance compared to commercial carbohydrate drink in hot humid conditions

“…The study showed that strong concentrations were not well tolerated by all participants (despite evoking a greater ‘cool’ sensation). A flavoured menthol gel of varying concentrations (0.1%–0.7%) also evoked a cooling sensation; however, again it was not well tolerated by all participants, with higher concentrations causing greater irritability (Vogel et al., 2022). Potentially, the co‐ingestion of carbohydrate and other components within the drink may dull the effect of menthol suggesting that when consumed at the very low 0.01% concentration, there was no impact.…”