To investigate the effects of the menstrual cycle and of exercise intensity on the relationship between finger blood flow (FBF) and esophageal temperature (Tes), we studied four women, aged 20-32 years. Subjects exercised at 40% and 70% VO2max in the semi-supine posture at an ambient temperature of 20 degrees C. Resting Tes was higher during the luteal phase than the follicular phase (P less than 0.01). There were no significant differences between the two phases in FBF, oxygen consumption, carbon dioxide production, heart rate or minute ventilation at rest and during exercise, respectively. Each regression line of the FBF-Tes relationship consists of two distinct segments of FBF change to Tes (slope 1 and 2). FBF increased at a threshold Tes for vasodilation ([Tes 0]) and the rate of FBF rise became greater at ([Tes 0]) and the rate of FBF rise became greater at another Tes above this threshold ([Tes 0']). For both levels of exercise, [Tes 0] and [Tes 0'] were shifted upward during the luteal phase, but the slopes of the FBF-Tes relationship were almost the same in the two phases of the menstrual cycle. Increasing exercise intensity induced a significant decrease in slope 1 of the FBF-Tes relationship during the follicular (P less than 0.01) and the luteal phases (P less than 0.02), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

This study examined the effect of local heating on the blood flow of the finger or forearm in male subjects in an environment of 35 degrees C--40% (r.h.). One hand or forearm was immersed in a water bath the temperature of which (Tw) was raised by 1 degrees C every 10th min from 35 degrees to 43 degrees C, while the other hand or forearm was kept at a constant Tw of 35 degrees C. Blood-flow (BF) was measured by venous occlusion plethysmography, using temperature-compensated mercury-in-Silastic strain gauges. Finger BF in the heated hand was significantly lower than that in the control hand at TwS of 37 degrees -41 degrees C, mostly for the first few minutes of each heating period. Thereafter, finger BF in the heated hand gradually returned toward the previous values. At TwS of 39 degrees -40 degrees C, however, finger BF in the heated hand remained lower than the control values for the entire period of heating. At TwS of 42 degrees -43 degrees C, finger BF in the heated hand greatly increased after an initial transitory fall. In the forearm skin, however, no such vasoconstriction in response to local heating was observed. All this suggests that a rise in skin temperature to above the core temperature produces paradoxical vasoconstriction in the finger, which may be a mechanism to reduce heat gain through the hand heated locally at higher temperatures.

Blood flows in the finger were measured simultaneously by laser Doppler flowmetry and by venous occlusion plethysmography in a warm environment (35°C, 40% RH). One hand was immersed in a water bath the temperature of which (TW) was raised every 10 min by steps of 2°C from 35 to 43°C, while the other hand was kept immersed in water at 35°C. Finger blood flow in the heated hand (BF) measured with venous occlusion plethysmography was significantly lower than that in the control hand (BFI) at TW of 39-41°C. At TW of 43°C, however, the finger BF W returned to the level of BFI after a transient decrease. In contrast, blood flow in the heated hand measured with laser Doppler flowmetry (LDFW) increased steadily as the TW was raised from 37 to 43°C, while that in the opposite hand (LDFC) remained unchanged. Assuming that the laser Doppler flowmetry does not measure blood flow through AVAs located deeply in the skin of the finger but measures flow through the superficial capillaries, the results suggest that the decrease in finger blood flow in response to local heating may be limited to AVAs, and superficial vessels may not contribute to this heat-induced vasconstriction of the finger.

To investigate the effects of hyperthermia and facial fanning during hyperthermia on hand-grip exercise performance and thermoregulatory response, we studied eight male subjects, aged 20-53 years. Subjects exercised at 20% of maximal hand-grip strength in the sitting position under three conditions: normothermia (NT), hyperthermia without fanning (HT-nf) or with fanning at 5.5 m X sec-1 wind speed (HT-f). Hyperthermia (0.5 degrees C higher oesophageal temperature than in NT) was induced by leg immersion in water at 42 degrees C. Mean exercise performance was markedly reduced from 716 contractions (NT) to 310 (HT-nf) by hyperthermia (P less than 0.01) and significantly (P less than 0.05) improved to 431 (HT-f) by facial fanning. Hyperthermic exercise was accompanied by significant increases in forearm blood flow (71%) and the local sweat rate on the thigh (136%) at the end of exercise compared with that in NT. Heart rate (HR) and rating of perceived exertion (RPE) increased during exercise and were higher in HT-nf than in NT at any given time of exercise. Oesophageal, tympanic (Tty) and mean skin temperatures were also significantly higher in HT-nf than in NT. Facial fanning caused a marked decrease in forehead skin temperature (1.5-2.0 degrees C) and a slight decrease in Tty, HR and PRE compared with that in HT-nf at any given time of exercise. These results suggested that hyperthermia increased thermoregulatory demands and reduced exercise performance. Facial fanning caused decreases in face skin and brain temperatures, and improved performance.

The metabolic response of warm-acclimated (25•Ž for 4 weeks) and cold-acclimated (5•Ž for 4 weeks) rats to infused norepinephrine (NE)