The extreme physical endurance demands and varied environmental settings of marathon footraces have provided a unique opportunity to study the limits of human thermoregulation for more than a century. High post-race rectal temperatures (Tre) are commonly and consistently documented in marathon runners, yet a clear divergence of thought surrounds the cause for this observation. A [...]
PURPOSE: This study evaluated the error produced by four commonly used field estimates and two prediction equations of total body sweat loss. METHODS: Eight women distance runners were studied during a 30-km treadmill run (approximately 70% .VO(2max)) in a warm (30 degrees C T(db)) and a cool (14 degrees C T(db)) environment. Total sweat loss [...]
This study investigated the effects of heat exposure, exercise-induced dehydration and fluid ingestion on cognitive performance. Seven healthy men, unacclimatized to heat, were kept euhydrated or were dehydrated by controlled passive exposure to heat (H, two sessions) or by treadmill exercise (E, two sessions) up to a weight loss of 2.8%. On completion of a [...]
ONTEXT: To our knowledge, no one has compared the prepractice hydration status of male and female National Collegiate Athletic Association (NCAA) Division I athletes or has studied the effects of the menstrual cycle phase on women's prepractice hydration status. OBJECTIVE: To report prepractice hydration status of collegiate athletes and determine the factors that might influence [...]
OBJECTIVE: The effect hydration status has on exposure to hypoxia is unclear. The purpose of the study was to identify how hydration status, above and below euhydrated levels, affects the physiological responses and onset of acute mountain sickness symptoms during acute normobaric hypoxia. METHODS: Eight males completed intermittent walking tests under normobaric hypoxic conditions (FIo2 [...]
CONTEXT: Previous field research has not identified sweat rates (SR), fluid consumption (FC), or the efficacy of an educational intervention (EI) for youth during football camp. OBJECTIVE: To measure hydration status and rehydration performance and examine EL using these data. DESIGN: Observational with EI randomized comparison. PARTICIPANTS: Thirty-three boys (mean +/- SD: 12 +/- 2 [...]
Rapid and complete rehydration, or restoration of fluid spaces, is important when acute illness or excessive sweating has compromised hydration status. Many studies have investigated the effects of graded concentrations of sodium and other electrolytes in rehydration solutions; however, no study to date has determined the effect of carbohydrate on fluid retention when electrolyte concentrations [...]
The impact of prior heat stress on subsequent aerobic exercise-heat performance has not been studied. PURPOSE: To determine whether prior heat stress degrades subsequent aerobic exercise performance in the heat. METHODS: Eighteen nonheat acclimated males were trained (four practice trials) on an aerobic exercise performance test in 22 degrees C and then divided into two [...]
PURPOSE: This study examined the utility of bioimpedance spectroscopy (BIS) for assessing total body water (TBW) changes associated with moderate (6-7% TBW), hypertonic (HH), and isotonic (IH) hypohydration. METHODS: The TBW of nine men was measured using BIS (TBWBIS) when euhydrated (EU) and during HH and IH. These measurements were compared with TBW measurements obtained [...]