These findings indicate that dynamic exercise may be an important adjunct in the treatment of mild hypertension.

We examined osmotic control of thirst and free water clearance in healthy older (65+, n = 10) and younger (Y, n = 6) subjects during a 3-h rehydration period after an approximately 2.4% decrease in body weight. Plasma volume (PV), plasma osmolality (Posm), renal function, and thirst were measured before and after dehydration and during rehydration. In 65+, baseline PV was lower (43.1 +/- 1.6 vs. 48.1 +/- 2.5 ml/kg), Posm was higher (287 +/- 1 vs. 281 +/- 2 mosmol/kgH2O), and perceived thirst was lower than in Y. During dehydration, the osmotic threshold for increased thirst was shifted to a higher Posm in 65+. Total fluid intake was greater in Y than in 65+ (16.6 +/- 4.1 vs. 8.9 +/- 2.0 ml/kg); however, the relation between thirst and the rate of fluid intake was identical. Thus the blunted rehydration in 65+ is related to a lower overall sensation of thirst. The stimulus-response characteristics of osmotic control of free water clearance was similar in 65+ and Y; however, 65+ operated around a higher Posm and on a less-steep portion of the stimulus-response curve. These data support the hypothesis that the hyperosmotic hypovolemic state of healthy older individuals is not a result of a simple water deficit but represents a shift in the operating point for control of body fluid volume and composition.

No abstract

The present study was conducted to examine the effects of acute aerobic exercise on smoking behavior. On alternate days, 10 healthy young smokers were subjected to half an hour of sustained high exercise (about 56% of maximum work capacity) or of low exercise (about 28% of maximum, simulating normal daytime activity). During the high-exercise condition, there were pronounced increases in physiological markers of physical activity such as mean work, heart rate, and lactic acid as well as elevations in circulating hormones (norepinephrine, epinephrine, and immunoreactive beta-endorphin and cortisol) known to be affected by vigorous exercise. Despite a trend toward decreased desire for cigarettes after the high exercise condition, there were no differences in plasma nicotine levels following the smoking of a usual-brand cigarette 35 min later. The sustained effects of the two exercise conditions were also similar: plasma cotinine levels 24 hr later (reflecting nicotine intake over the entire exercise day) revealed no significant differences between high and low exercise.