11 Hydration, Thermoregulation, Gastric Emptying Principles_updated

Euhydration

Normal body water content within homeostatic range.

Dehydration

The process of dynamic loss of body water, e.g., the transition from euhydration to hypohydration.

Rehydration

The process of dynamic gain of body water through fluid intake, e.g., the transition from hypohydration to euhydration.

Hypohydration

A state of body water deficit.

Hyperhydration

A state of body water excess.

Total Body Water (TBW)

Approximately 50-70% of body mass, calculated as ~0.73 x fat free mass.

ADH (Antidiuretic Hormone)

Hormone released by the posterior pituitary promoting water conservation by increasing plasma volume.

Aldosterone

Hormone released by the adrenal cortex that promotes sodium reabsorption in kidneys to increase plasma volume.

Sweat Rate

Rate at which sweat is produced, approximately 1-2 L/h.

Hyponatremia

Low blood sodium that can occur from excessive water intake, leading to symptoms such as confusion and possible brain swelling.

Fluid Balance Control

Mechanisms that allow the body to retain or excrete body water, monitored by osmoreceptors and volume receptors.

Hypertonic Blood

Blood with relatively high concentrations of sodium, protein, or glucose which can draw water out of cells.

Gastric Emptying Factors

Factors influencing the rate at which the stomach empties its contents, including gastric volume and exercise intensity.

Urine Color as Hydration Indicator

Urine color can be used to assess hydration status, with darker urine indicating hypohydration.

Sodium's Role in Fluid Balance

Sodium controls water movement between fluid compartments and stimulates thirst to maintain proper hydration.

Fluid Loss During Exercise

Includes loss through sweat, urine, and respiration, critical to monitor for maintaining hydration.

Pelvic Fluid Volume

Refers to the total volume of fluid (water and electrolytes) in the body's compartments, affecting hydration status.

Rehydration Recommendations

After exercise, it is advised to replace 20-24 oz of fluid for every pound lost to restore hydration.

Monitoring Hydration Status

Methods include tracking urine color, body mass changes, and specific gravity to assess hydration levels.

Thirst Sensation Deferment

Thirst is often a poor indicator of hydration needs, typically arising only after significant body water loss.

Effects of Dehydration on Performance

Dehydration can impair heat removal, increase cardiovascular strain, and decrease cognitive functions.

Effects of Hyperhydration

Can lead to dilution of sodium concentration in blood and might result in cellular edema.

Hydration Assessment Before Exercise

Includes checking for thirst, urine color, and body mass changes to determine hydration needs.