2007, Piran, Slovenia

Thermal comfort
THERMAL SENSATIONS OF FACE OF STANDING AND
EXERCISING SUBJECTS DURING WHOLE BODY EXPOSURES TO
COLD AND WIND
Hannu Rintamäki 1,2 , Tero Mäkinen 1 , Désirée Gavhed 3 and Ingvar Holmér 4
1 Finnish Institute of Occupational Health, Oulu, Finland
2 Department of Physiology, University of Oulu, Oulu, Finland
3 National Institute for Working Life, Stockholm, Sweden
4 Thermal Environment Laboratory, Department of Design Sciences,
Lund Technical University, Lund, Sweden.
Contact person: hannu.rintamaki@ttl.fi
INTRODUCTION
Thermal sensations are associated with skin temperatures. However, the relationship is not
constant but modified by cooling rate, surface area of cooled/warmed site, site of
cooling/warming (due to different number of thermoreceptors), adaptation of
thermoreceptors, thermal acclimatization or acclimation (Hensel 1981) and age (Stevens and
Choo 1998). When asking the judgement of thermal sensation in cold conditions, it has been
observed that the temperature of the coldest point of the given body area dominates the
expressed thermal sensation (Rintamäki and Hassi 1989). It has also raised the possibility that
heat flux from the skin, instead of skin temperature, determines thermal sensations.
Face skin temperatures seem to be especially important in cold exposure, as physiological
responses, like blood pressure rise, starts immediately after exposure to cold, although other
body parts than the face are not cooled in properly clothed subjects. In the present study the
thermal sensations of face were studied during different combinations of wind and exercise
with initially thermoneutral or pre-cooled subjects to see the possible effects of cooling rate
and metabolic heat production on the sensations in well-clothed subjects.
METHODS
Eight healthy men served as test subjects: 23 (SD 2) y, 179 (4) cm, 73 (7) kg and body fat 14
(3) %. Each subject arrived in laboratory at the same time of the day. After being equipped
with the instruments, the subjects donned standard Finnish military three-layer winter
clothing, with thermal insulation of ~2.2 clo. During preconditioning, the subjects sat in a net
chair for 60 min either at 20°C (thermoneutral preconditioning, TN) or at -5°C (cold
preconditioning, C). During TN preconditioning hat, gloves, jacket and boots were not worn
to avoid heat gain. After preconditioning the subject went to a wind tunnel and stand there for
30 min, facing towards wind, or walked on a treadmill for 60 min at 2.8 km h -1 with 0°
inclination (light exercise, metabolic rate 124 W·m -2 ) or 6° (moderate exercise, metabolic rate
195 W·m -2 ). Each measurement was carried out at wind velocity of 0.2, 1.0 and 5.0 m·s -2 .
Each subject was exposed to the combinations of wind speed and exercise intensity in a
randomized order. Skin temperatures (from the face: cheek, forehead, nose) and heat flux
(from the face: forehead) were measured continuously and stored at 1 min intervals. Thermal
sensations (ISO 10551) were recorded at 10 min intervals. The details of the measurements
are described by Mäkinen et al. (2000, 2001).
RESULTS
Thermal sensations of the face usually had the best correlation with cheek temperature (Table
1). Only during light exercise the correlation was slightly higher with forehead temperature.
Other measured parameters had much lower correlation with thermal sensations. Stepwise
regression analysis produced the same result: other parameters could not significantly
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