Thermal basis of finger blood flow adaptations during abrupt perturbations in thermal homeostasis.

The objective of this experiment was to assess whether reflex alterations in finger blood flow during repetitive hot and cold water immersion are associated with changes in rectal, tympanic, mean body temperature or heat storage. Fifteen healthy adults (eight males) volunteered. Following a 15-minute baseline period, participants were immersed in 42°C water and passively rested until their rectal temperature was raised by 0.5°C above baseline. Thereafter, they were immersed in a different water tank maintained at 12°C water temperature until their rectal temperature was decreased by 0.5°C below baseline. This procedure was conducted twice. Auto-Regressive Integrated Moving Average analysis showed that fluctuations in finger blood flow were associated with changes in mean body temperature (Ljung-Box statistic >0.05; R² = 0.67) and body heat storage (Ljung-Box statistic >0.05; R² = 0.70), but not with rectal (Ljung-Box statistic <0.05; R² = 0.54) or tympanic (Ljung-Box statistic <0.05; R² = 0.49) temperatures. It is concluded that reflex alterations in finger blood flow during repetitive hot and cold water immersions are associated with mean body temperature and the rate of body heat storage, but not with rectal and tympanic temperatures.