2007, Piran, Slovenia

Environmental Ergonomics XII
Igor B. Mekjavic, Stelios N. Kounalakis & Nigel A.S. Taylor (Eds.), © BIOMED, Ljubljana 2007
CHROME DOMES: SWEAT SECRETION FROM THE HEAD DURING
THERMAL STRAIN.
Christiano A. Machado-Moreira 1 , Frederik Wilmink 1 , Annieka Meijer 1 , Igor B. Mekjavic 2 ,
Nigel A.S. Taylor 1
1 Human Performance Laboratories, University of Wollongong, Wollongong, Australia and
2 Jozef Stefan Institute, Ljubljana, Slovenia.
Contact person: nigel_taylor@uow.edu.au
INTRODUCTION
The importance of the head in dissipating body heat and the prevention of heat illness under
hot conditions is well recognised (Desruelle and Candas, 2000), although little is known about
the local differences in sweat secretion within the head. In this study, we focussed on this
sweat distribution, since such information will contribute significantly to our understanding of
thermoregulation in general and of human sudomotor control in particular.
Despite its relatively small surface area (6-7% of total area; Hardy and DuBois, 1938), the
head is highly vascular, and has a surface area-to-mass ratio that favours heat loss. Indeed,
heat loss per unit area is significantly higher from the head than most other body segments
(Froese and Burton 1957; Rasch et al., 1991). In addition, when the body is covered with
clothing, the head becomes a major avenue for heat dissipation, but this is adversely
influenced by helmets and other headgear. Therefore, it is most important, either for the
development of thermal (head) manikins or for the design of headgear, that the sweat
secretion patterns of the head are known across a wide range of thermal loads. In this project,
the sweating responses of nine non-glabrous (hairy) skin surfaces of the scalp and the
forehead were measured in shaved males.
METHODS
Ten healthy and physically-active males (25.5 SD 2.7 y; 74.8 SD 8.4 kg; 178.7 SD 9.0 cm)
participated in hot-humid trials (36 o C, 60% relative humidity) involving 30 min rest, followed
by incremental cycling (increasing from 50 W by 25-W steps every 15 min), whilst wearing a
heated water-perfusion garment (46 o C: Cool Tubesuit, Med-Eng, Ottawa, Canada). Before
testing, each subject’s head was shaved and instrumented. Trials were terminated when core
temperature exceeded 39.5 o C for 2 min (N=1) or at volitional fatigue (N=9). The average
exercise duration was 55.6 min (range: 45-69 min).
Ventilated sweat capsules (3.16 cm 2 ) were used to measure local sweat rates from the
forehead, and nine sites inside the hair line: three lateral sites on each side; two top sites; one
rear site (Figure 1; Clinical Engineering Solutions, NSW, Australia). Local sweat rates were
recorded from six sites simultaneously, with the four remaining sweat capsules ventilated
with room air to avoid saturation. During rest, only six sites were investigated, while during
exercise, capsules were connected to the sweat system in a rotating pattern, leaving two
capsules always connected. Two trial sequences were established, with five subjects
participating in each sequence. Capsule changes were completed within about 2 min, and this
rotation pattern was continued until the trial terminated.
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