TITLE:
Effects of dry and mist saunas on circulatory and thermoregulatory functions in humans
AUTHORS:
Satoshi Iwase, Yuko Kawahara, Naoki Nishimura, Hiroki Takada, Mayumi Nagata, Yuki Niimi, Chihiro Miwa
KEYWORDS:
Sauna Bathing; Mist Sauna; Dry Sauna; Heat Stress; Hemodynamic Change; Thermoregulatory Function
JOURNAL NAME:
Health,
Vol.5 No.2,
February
28,
2013
ABSTRACT: To test the hypothesis that mist sauna is a safer way of
bathing than dry sauna, we compared changes in circulatory and thermoregulatory
functions during 10 min sauna bathing in mist sauna at 40℃ with relative
humidity of 100%, and in dry sauna by infrared ray at 70℃ with relative
humidity of 15%. Subjects were seven healthy young men aged 29 ± 6 yrs (mean ±
SD). We measured blood pressure, heart rate, skin temperatures at chest,
forearm, thigh, and leg, tympanic temperature (Tty) by thermistors, skin blood
flow at forearm by laser Doppler flowmetry, and sweat rate by ventilated
capsule method at 1 min intervals throughout the experiment. Total sweating and
change of hematocrit were also measured for dehydration analysis. Blood pressure
was elevated more and changes in heart rate and total sweating were larger in
dry sauna than mist. A significant hematocrit increase was observed in dry
sauna bathing only. Mean skin temperature and Tty in dry sauna were elevated
higher than those in mist. Heat stress of the dry sauna may be stronger than
that of the mist, leading to dehydration and hypovolemia by sweating. Percent
plasma volume loss was significantly larger in the dry than mist sauna.
Changes in skin blood flow and sweat rate/Tty during mist sauna were
significantly larger than those during dry sauna bathing despite heat stress of
the mist sauna. The mist sauna bathing may thus be safer physiologically, and
provide more effective vascular dilatation and sweating than the dry sauna
bathing.