2007, Piran, Slovenia

Cold physiology
SKIN SURFACE MENTHOL APPLICATION ENHANCES EXERCISE-
INDUCED MILD HYPERTHERMIA
Botonis Petros, Kounalakis Stelios, Koskolou Maria, and Geladas Nickos
Department of Sports Medicine & Biology of Exercise, Faculty of Physical Education and
Sport Science, University of Athens, Greece
Contact person: ngeladas@phed.uoa.gr
INTRODUCTION
Menthol application on lingual membranes enhances the firing frequency of cold receptors
(Hensel and Zotterman 1951). At rest, application of menthol on the skin stimulates coldsensitive
afferent pathways (Shafer et al., 1986), which may activate norepinephrine release,
leading to local cutaneous vasoconstriction. On the other hand, the thermogenic effect of
sustained exercise induces vasodilation at the periphery for thermoregulatory purposes. It is
not known however, whether application of menthol, a widespread ingredient of various
cosmetic and therapeutic skin creams, could impede thermoregulation during exercise. The
purpose of the present study was to investigate the effect of skin surface menthol application
on rectal temperature rise during exercise. It was hypothesized that menthol application would
enhance heat gain during steady state cycling, mainly via peripheral vasoconstriction.
METHODS
The experiments for each subject were conducted at the same time of day, at least 3 hours
after a light meal. After the subjects emptied their bladder, their body mass was measured
(Bilance Salus, Milano) and a thermistor (Yellow Springs, USA) was placed in the rectum, at
a depth of 13-15 cm from the sphincter. Thermistors (Yellow Springs, USA) on forearm and
fingertip were placed and secured with an adhesive tape while subject was seated and relaxed
on the bicycle. Following this preparation, 5 min resting values for HR (Polar S-810,
Finland), VO2 (MedGraphics, CPX-D, USA), and temperatures were obtained. Afterwards,
each subject cycled at 50% of his maximum HR (220-age), so long as to reach 38 oC in Tre.
In menthol condition, the 5 min resting period was followed by menthol application of (4.6 ml
per 100 ml) of water on the skin all over the body. Subsequently, menthol-resting data were
collected for another 5 min. All experiments were conducted at similar environmental
temperature (24.1±1.0 oC) and relative humidity (46.2±4.3 %).
RESULTS
Throughout exercise, power output and HR were similar between conditions. The mean
power output was 139.5±8 Watt in menthol and 150.6±9 Watt (p=0.3) in control condition;
Table 1. Cycling time to reach 38 o C, rectal temperature (Tre) at rest, the rate of rise in rectal
temperature, oxygen consumption (VO2) at rest and during 12 th min exercise (VO2 1-12 th ) in
menthol and control conditions. Values are means ± SD.
Menthol Control p-value
Cycling time (min) 19.0±2.0 29.1±1.0 0.001
Tre rest ( o C) 37.32±0.3 37.14±0.3 0.89
Tre rise ( o C·min -1 ) 0.24±0.09 0.14±0.09 0.03
VO2 rest (ml·min -1 ) 327±53 357±39 0.32
VO 2 1-12 th min (ml·min -1 ) 1890±352 1745±330 0.03
325