REF-965 · Barwood et al., 2019 · International Journal of Sports Physiology and Performance, Vol. · Paper · PubMed

Enhancement of Exercise Capacity in the Heat With Repeated Menthol-Spray Application

Blimited evidenceMeasured on trained to highly trained athletesWritten before October 2026, being re-checked

Eight trained cyclists each did two trials in dry heat (35°C, 22% relative humidity): 45 min of fixed-intensity riding at 50% of maximal power output, then a test to exhaustion (TTE) at 70% of maximal power output; 100 mL of either menthol spray (0.20% menthol) or a control spray went onto the torso at 20 and 40 min.

Menthol made thermal sensation better (P = .008) but changed thermal comfort only descriptively (P = .173). With menthol, sweat production and sweat rate were lower and TTE performance was better (4.6 [1.74] vs 2.4 [1.55] min; P = .004). Despite the repeated sprays, their effects faded.

The authors conclude that spraying menthol repeatedly improves exercise capacity yet changes thermoregulation, so it should be used with care.

Participants

n=8 trained cyclists. Sex, age and fitness values are not given in the abstract.

Protocol

Two separate conditions: menthol spray (0.20% menthol) vs control spray; 100 mL applied to the torso after 20 and 40 min.
Fixed-intensity cycling at 50% maximal power output for 45 min, then a test to exhaustion at 70% maximal power output.
Environment: hot (35°C), dry (22% relative humidity).
Measures: thermal sensation, thermal comfort, rating of perceived exertion; TTE duration; skin temperature, rectal temperature, cardiac frequency; sweating.

Key Results

MeasureMenthol sprayControl sprayP
Test to exhaustion4.6 [1.74] min2.4 [1.55] min.004
Sweat production994 [380] mL1180 [380] mL.020
Sweat rate827 [327] mL·h-1941 [319] mL·h-1.048
Thermal sensationcold sensation (after first spraying)warm/hot.008
Thermal comfortcomfortableuncomfortable.173 (descriptive only)
Menthol-spray effects diminished despite repeated applications; the authors attribute this to an increased contribution of visceral thermoreceptors to thermal perception.
Rectal temperature was measured; no result for it is given in the abstract.

Practical Application

In eight trained cyclists riding in 35°C and 22% relative humidity (crossover), spraying 0.20% menthol on the torso twice during 45 min of steady riding extended a following test to exhaustion (4.6 vs 2.4 min, P = .004) and made them feel cold rather than warm/hot, while sweat production (994 vs 1180 mL) and sweat rate (827 vs 941 mL·h-1) were lower. To "does a menthol spray help in the heat?": it lengthened a short exhaustion test here, and it did so while the body sweated less — the authors' own conclusion is that care should be taken with its use.
The perceptual effect faded with the second application, so repeating the spray does not keep the feeling going.
The authors also note the logistical burden of carrying and deploying a spray, to be weighed against the benefit.
Inference, not tested here: less sweating with a cooler feeling in hot conditions means less evaporative heat loss at the moment the athlete feels able to push harder; the abstract reports no rectal-temperature result to confirm or rule out a rise.
Not from this paper: a later trial from the same lead author with a whole-body gel found sweating increased and no performance gain (REF-966); pooled topical evidence is in REF-963; the base's protocol is in SYNTH-25.

Limitations

n=8; sex not stated; randomisation and blinding not stated in the abstract (a menthol spray is hard to blind).
A test to exhaustion lasting a few minutes after 45 min of steady riding, in one hot, dry condition — not a time trial and not humid heat.
No rectal-temperature result in the abstract, so the consequence of the lower sweating for body temperature is not shown.
Written from the abstract and record metadata only (full text not read).
How this entry was checked and changed
Why this level

crossover, n=8; randomisation and blinding are not stated in the abstract