Ralph P. Francesconi

Effects of water temperature and flavoring on voluntary dehydration in men

Effects of water temperature and flavoring on fluid consumption and body weight losses were studied in fourteen unacclimatized men (21-33 years) during 6 hr of treadmill exercise (4.8 km.hr-1, 5% grade for 30 min.hr-1) in a hot environment. Subjects consumed each of four beverages (15 degrees C water, 40 degrees C water, 15 degrees C flavored water, and 40 degrees C flavored water) on four nonconsecutive days. We identified two groups of individuals by body weight (BW) loss during the cool water trial: drinkers (D) who lost less than 2% initial BW (0.80 +/- 0.15%) and reluctant drinkers (RD) who lost more than 2% (2.53 +/- 0.12%). Although sweat losses were not different between the two groups, D consumed 31% more cool water than RD and experienced 68% less BW loss. Compared to the warm water trial, 6 hr consumption of cool water was significantly increased in both D (59%) and RD (141%) and BW loss was dramatically reduced in both groups. Flavoring significantly enhanced warm water consumption and reduced BW loss in RD only. Reduced consumption of warm water increased rectal temperature, heart rate and plasma osmolality in both groups. The results of this study indicate that either flavoring or cooling warm water will enhance fluid intake and reduce body weight deficits in men reluctant to drink.

Effects of acute plasma volume expansion on altering exercise-heat performance

SummaryTo determine the effect an acute plasma volume expansion has on body temperature responses and exercise performance in the heat, seven unacclimatized male volunteers attempted to complete two 90-min walks (45% of

Circadian variations in plasma renin activity, catecholamines and aldosterone during exercise in women.

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A role for carnitine and long chain acylcarnitine in the regulation of lipogenesis

max) in a hot/dry (45‡ C/20% rh) environment. The experimental walk was preceded by an infusion of human albumin (50 g in a 200-ml solution) and the control walk was preceded by an infusion of isotonic saline (200 ml). Saline infusion did not alter the plasma volume. The albumin infusion was found to significantly (p<0.01) increase plasma volume ~ 13% over control levels. No significant differences were found for performance time, final heart rate or final rectal temperature values between the two walks. In general, significant differences were not found for systolic blood pressure, rectal temperature, mean skin temperature, heat storage, sweat rate, plasma lactate, plasma osmolality, or plasma protein content values between the two walks. However, heart rate responses were found to be significantly lower (p<0.05; ~ 13 bt·min−1) during the 25-min and 40-min measurements of the experimental walk. These data suggest that plasma volume expansion may be a supportive adaptation to enable lowered heart rate responses but does not improve thermoregulatory function or performance time in the heat.

Thermoregulatory effects of centrally administered bombesin, bradykinin, and methionine-enkephalin

De-emphasis of the role of anhydrosis as the primary cause of heatstroke has resulted in increased usage and acceptance of animal models for heatstroke research. When the total amount of work achieved by the running rat prior to exhaustion was plotted against the rate of heat storage, a heretofore unrecognized relationship emerged. These new data suggest that physical exhaustion and heat exhaustion represent opposite ends of a continuum related to the rate of heat storage. Changes in thermoregulatory and/or physical performance can be estimated by a two-dimensional shift in the work-output/thermal storage ratio. Potassium depletion reduces thermoregulatory/physical performance; a combination of atropine plus diazepam appears to improve it. The role of the cholinergic nervous system in eliciting alterations in thermoregulatory and physical ability is reviewed; endurance training, shivering, acclimatization, set-point theory, the anticholinergic syndrome, lithium intoxication, and choline deficiency are discussed.

Effect of nitric oxide synthase inhibition on regional blood flow during hyperthermia.

SummaryFour women were studied at 0400 h and 1600 h to determine if their hormonal and hemodynamic responses to exercise varied with the circadian cycle. Esophageal temperature was measured during rest and exercise (60% peak

Atropine, diazepam, and physostigmine: Thermoregulatory effects in the heat-stressed rat

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