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1 Centre for Research & Technology
2 Dalhousie University
* To whom correspondence should be addressed. E-mail: aflouris{at}cereteth.gr.
We examined the effect of thermal balance perturbation on cold-induced vasodilation through a dynamic A-B-A-B design applying heat (condition A) and cold (condition B) to the body's core while the hand is exposed to a stable cold stimulus. Fifteen healthy adults (8 males, 7 females) volunteered. Applications of heat and cold were achieved through water immersions in two tanks maintained at 42°C and 12°C water temperature, respectively, in an A-B-A-B fashion. Throughout the experiment, the participants' right hand up to the ulnar styloid process was placed inside a temperature-controlled box set at 0°C air temperature. Results demonstrated that cold-induced vasodilation occurred only during condition B and at times when body heat content was decreasing but rectal temperature had not yet dropped to baseline levels. Following the occurrence of all cold-induced vasodilation events, rectal temperature was reduced and the phenomenon ceased when rectal temperature fell below baseline. Heart rate variability data obtained prior to and during cold-induced vasodilation demonstrated a shift of autonomic interaction towards parasympathetic dominance which, however, was attributed to a sympathetic withdrawal. Receiver operating characteristics curve analyses demonstrated that the cold-induced vasodilation onset cut-off points for rectal temperature change and finger temperature were 0.62°C and 16.76°C, respectively. It is concluded that cold-induced vasodilation is a centrally originating phenomenon caused by sympathetic vasoconstrictor withdrawal; it is dependent on excess heat, and it may be triggered by excess heat with the purpose of preserving thermal balance.
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