During prolonged exercise, fluid and salt losses through sweating reduce plasma volume which leads to heart rate drift in association with hyperthermia and reductions in performance. Oral rehydration with water reduces the loss of plasma volume and lessens heart rate drift and hyperthermia. Moreover, the inclusion of sodium in the rehydration solution to levels that [...]
OBJECTIVE: Reduced intake of sweetened caloric beverages (SCBs) is recommended to lower total energy intake. ReplacingSCBs with non-caloric diet beverages does not automatically lower energy intake, however. Compensatory increases in other food or beverages reportedly negate benefits of diet beverages. The purpose of this study was to evaluate drinking water as an alternative to SCBs. RESEARCH METHODS AND PROCEDURES: Secondary analysis of data from the Stanford A TO Z intervention evaluated change in beverage pattern [...]
Although much is known about the effects of changes in electrolyte and water balance on serum sodium concentration, the quantitative relationships between body composition and the concentration of sodium in serum have not been established. Also, no definitive study has been made of the correspondence between serum sodium concentration and total serum osmolarity. It is [...]
Evolution has provided an elaborate network of regulatory systems that stabilize body-fluid volume, temperature and composition. This stability insulates cells from an ambient hostile world and assures them the best possible conditions in which to function optimally. When one of these regulatory systems fails, cells and even whole organ systems cannot function properly. This paper [...]
The chronology of hemoconcentration and hemodilution associated with changes in posture, and the reliability of venous hematocrit (Hct), hemoglobin (Hb), and plasma proteins (PP) as indicators in evaluating changes in plasma volume were determined in seven male subjects. Red cell mass was also measured by the CO method at the termination of the erect and supine positions. Movementto and from supine and erect positions produced consistent, rapid, and progressive changes in Hct, Hb, [...]
BACKGROUND: Data from short-term experiments suggest that drinking water may promote weight loss by lowering total energy intake and/or altering metabolism. The long-term effects of drinking water on change in body weight and composition are unknown, however. OBJECTIVE: This study tested for associations between absolute and relative increases in drinking water and weight loss over 12 months. METHODS AND PROCEDURES: Secondary analyses were conducted on data from the Stanford A TO Z weight loss intervention [...]
This study examined the effect of glycerol ingestion on fluid homeostasis, thermoregulation, and metabolism during rest and exercise. Six endurance-trained men ingested either 1 g glycerol in 20 ml H2O x kg(-1) body weight (bw) (GLY) or 20 ml H2O x kg(-1) bw (CON) in a randomized double-blind fashion, 120 min prior to undertaking 90 min of steady state cycle exercise(SS) [...]
This study investigated the hypothesis that addition of Na+ to a rehydration beverage would stimulate drinking and augment restoration of body water in individuals dehydrated during 90 min of continuous treadmill exercise in the heat. Following a 3.0 +/- 0.2% decrease in body weight (BW), 6 subjects sat in a thermoneutral environment for 30 min to allow [...]
This paper reviews the literature, describes and discusses methods by which whole body hydration status can be determined in humans. A method of determining whether or not an individual is hypohydrated is of particular significance in an exercise situation as even moderate levels of hypohydration have a negative impact on exercise performance. Inspection of the published literature [...]