2007, Piran, Slovenia

Environmental Ergonomics XII
Igor B. Mekjavic, Stelios N. Kounalakis & Nigel A.S. Taylor (Eds.), © BIOMED, Ljubljana 2007
EFFECT OF NON-UNIFORM SKIN TEMPERATURE ON
THERMOREGULATORY RESPONSE DURING WATER IMMERSION
Hitoshi Wakabayashi 1 , Koichi Kaneda 2 , Daisuke Sato 2 , Yutaka Tochihara 1 and
Takeo Nomura 2
1 Kyushu University, Fukuoka, Japan, 2 University of Tsukuba, Tsukuba, Japan
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Contact person: waka78421@yahoo.co.jp
INTRODUCTION
The thermal conductance of water is approximately 25 times greater than that of air.
Consequently, body heat is rapidly conducted away from human skin to the water. Wearing
an additional layer of insulation on the skin surface is a convenient means to reduce
convective heat loss. Many investigators have studied the effects of wetsuits, which reduced
the decrease of core temperature (Kang et al., 1983; Shiraki et al., 1986). In our previous
studies, we investigated the effects of a partial coverage wetsuit (PCWS, or thermal
swimsuit) during cool water immersion (Wakabayashi et al., 2005; Wakabayashi et al., 2006;
Wakabayashi et al., 2007), and compared them with the responses observed with a wetsuit.
The tissue insulation (Itissue) with a partial coverage wetsuit (PCWS) was similar to the naked
condition, while previous studies reported that wearing wetsuits decreased Itissue (Kang et al.,
1983; Shiraki et al., 1986). While wearing a PCWS the distal extremities are exposed to
water more than in wetsuits, which might be a sufficient sensory input to induce
vasoconstriction similar to the naked condition. Choi et al. (2003) studied the effect of
uniform and non-uniform skin temperature on thermal exchanges in water using a specially
designed water-perfused garment and thermo-circulation system, which controlled five skin
temperature regions individually. They reported that the higher skin temperature of the trunk
attenuates shivering in cold water compared to the uniform condition at the same mean skin
temperature.
The present study investigated the effect of non-uniform skin temperature distribution
wearing a PCWS on thermoregulatory responses during water immersion.
METHODS
Ten healthy male subjects volunteered for this study. Each subject participated in two trials:
in one the skin temperature was uniform (uniform skin temperature, UST), and in the other it
was not (non-uniform skin temperature, NUST). In the UST condition, subjects with ordinary
swim trunks were immersed up to the level of their neck level for 60 min in 29°C water. In
the NUST condition, subjects wore a PCWS during immersion in 26°C water. In both
conditions, their mean skin temperatures were similar. The PCWS used in this study was
made of nylon-faced neoprene (2 mm thick), covered trunks, upper arms, thighs, and neck.
During the experiment, esophageal temperature (Tes) and 8 skin temperature regions were
measured using thermistor sensors. The mean skin temperature ( T sk ), the skin temperature of
the trunk and proximal extremities ( T trunk ) and the distal extremities ( T limb ) were calculated.
The mean body temperature ( T b ) were calculated from Tes and T sk .
Expired gases were continuously assessed using an automatic respiromonitor. Values of
oxygen uptake ( VO2 & ), carbon dioxide elimination ( VCO 2
& ), and respiratory exchange ratio
(RER) were averaged every 1 min. Total metabolic heat production (M) was calculated from
V& and RER. Metabolic heat production from the unit skin surface (Ms) was calculated using
O2