Effect of exercise intensity on active and passive glucose absorption.

The purpose of this study was to determine the effects of exercise intensity on active and passive intestinal glucose absorption. Eight trained runners (age = 23 +/- 2 y; VO2max = 62.1 +/- 5.

Accuracy of urine specific gravity and osmolality as indicators of hydration status.

To reduce the adverse consequences of exertion-related and acute intentional dehydration research has focused on monitoring hydration status. This investigation: 1) compared sensitivity of urine specific gravity (Usg), urine osmolality (U(osm)) and a criterion measurement of hydration, plasma osmolality (P(osm)), at progressive stages of acute hypertonic dehydration and 2) using a medical decision model, determined whether Usg or U(osm) accurately reflected hydration status compared to P(osm) among 51 subjects tested throughout the day. Incremental changes in P(osm) were observed as subjects dehydrated by 5% of body weight and rehydrated while Usg and U(osm) showed delayed dehydration-related changes.

Peripheral vascular responses to heat stress after hindlimb suspension.

Purpose: The purpose of this study was to determine whether hindlimb suspension (which simulates the effects of microgravity) results in impaired hemodynamic responses to heat stress or alterations in mesenteric small artery sympathetic nerve innervation.

Methods: Over 28 d, 16 male Sprague-Dawley rats were hindlimb-suspended, and 13 control rats were housed in the same type of cage. After the treatment, mean arterial pressure (MAP), colonic temperature (Tcol), and superior mesenteric and iliac artery resistances (using Doppler flowmetry) were measured during heat stress [exposure to 42 degrees C until the endpoint of 80 mm Hg blood pressure was reached (75 +/- 9 min); endpoint Tcore = 43.

Is the GI System Built For Exercise?

The gut usually meets the fluid, electrolyte, and nutrient requirements of mild to heavy exercise. Gastric emptying and intestinal absorption rates of beverages ingested during exercise equal sweat rates. However, strenuous or prolonged exercise under dehydrated conditions can produce gastrointestinal distress and tissue damage.