2007, Piran, Slovenia

Cold physiology
THE EFFECT OF EXERCISE-INDUCED HYPERTHERMIA ON THE
FINGER SKIN COLD-INDUCED VASODILATATION RESPONSE
Uroš Dobnikar 2 , Stelios Kounalakis 1,3 & Igor B. Mekjavic 1
1 Institute of Jožef Stefan, Ljubljana; 2 Clinical Centre Maribor; 3 National and Kapodistrian
University of Athens, Greece;
Contact person: igor.mekjavic@ijs.si
INTRODUCTION
It is generally accepted that cold induced vasodilatations (CIVD) in fingers play a role in cold
injury prevention. The mechanism of CIVD has not yet been resolved. The actual
morphological structures responsible for CIVD also remain to be defined. Despite the many
uncertainties regarding the etiology and morphology of the CIVD response, the arteriovenous
anastomoses have been implicated as contributing significantly to the response. CIVD has
been extensively studied in fingers (Daanen 2003). Unfortunately, CIVD in toes has attracted
less scrutiny, despite the higher incidence of cold injuries in the toes.
The purpose of this study was to evaluate the effect of moderate exercise-induced
hyperthermia on toe skin temperatures during immersion of the foot in cold (8°C) water.
METHODS
Eight young male students, with average (SD) age of 25 (5) years, height 180.8 (4.8) cm, and
weight 80.4 (5.9) kg gave their informed consent to participate. The National Medical Ethics
committee of the Republic of Slovenia approved the study. Written informed consent was
obtained from all subjects. Participation in the study was subject to physician’s approval.
The subjects were asked to abstain from caffeine 2 hours before the trials. They were also
asked not to participate in any sporting activity, and not to perform any heavy physical
exertion at least 2 hours before the trials.
All subjects participated in two trials in a counterbalanced order, separated by at least two
days. In the hyperthermic experiment, the core temperature of the subjects was raised by an
incremental cycling exercise (Monark 884E, Sweden) with 40 Watts increments every 2 min
to exhaustion. Exercise was followed by an 8 o C cold-water immersion of the right foot for 30
minutes. In the normothermic experiment, the immersion of their right foot in cold water was
not preceded by exercise. The two trials were conducted at the same time of day, in
environmental temperature of 27 °C and relative humidity of 35 %.
During the experiments, the pad skin temperature of all toes and the dorsum of the foot were
measured every 8 seconds with thermocouples (Almemo, Ahlborn, Germany). Tympanic
temperature (ThermoScan, Braun, Germany), heart rate (Polar NV, Polar Electro Oy,
Finland), and subjective ratings of thermal comfort and temperature sensation were also
monitored during the immersions.
RESULTS
Subjects cycled for 9.2 (2.3) min and reach the maximal work rate of 221.2 (45.2) Watts.
During the hyperthermic trial, tympanic temperature was higher by 0.55 oC compared to
normothermic trial. Tympanic temperature remained significantly higher during the 30 min
immersion in the hyperthermic compared to the normothermic trial. A CIVD response
occurred in 57.5% of all toes in the hyperthermic trial, and in only 27.5% in the normohermic
315