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Bob Murray, John Stofan and Bob Sallis


This article summarizes a case of ischemic colitis suffered by a triathlete during an Ironman competition.


Exercise results in a significant reduction in splanchnic blood flow to help maintain cardiovascular function. When dehydration and heat stress accompany exercise, blood flow to the splanchnic vasculature is further reduced, increasing the risk of local ischemia and tissue injury.

Differential Diagnosis:

Ischemic colitis caused by dehydration and heat stress.


Right hemicolectomy involving a 16-cm segment of ischemic large intestine and appendectomy the day following the race.


This case study highlights one of the risks associated with dehydration during prolonged exercise in the heat. Of particular interest are practical interventions to reduce health and performance issues.


Poor hydration and nutrition practices during intense exercise can affect gut function, impair performance, and jeopardize health. Optimal intake of fluid, carbohydrate, and salt will enhance performance and reduce risk to health.

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Damir Zubac, Drazen Cular and Uros Marusic

official weigh-in) to discourage aggressive weight-reduction despite the tragic events in combat sports, including death. 3 , 4 Recently, Reljic et al 5 proposed that adverse health-related issues in adolescent boxers originate from body-fluid manipulations, primarily achieved by acute dehydration, to

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Giannis Arnaoutis, Panagiotis Verginadis, Adam D. Seal, Ioannis Vogiatzis, Labros S. Sidossis and Stavros A. Kavouras

Maintaining fluid homeostasis is vital for optimal athletic performance in both youth and adults. The loss of plasma volume (hypovolemia) concomitant with dehydration results in cardiovascular and thermoregulatory strain due to elevation of heart rate and decrease in cardiac output, ultimately

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Julian A. Owen, Matthew B. Fortes, Saeed Ur Rahman, Mahdi Jibani, Neil P. Walsh and Samuel J. Oliver

No consensus currently exists on the best method to assess dehydration and prescribe fluid intake ( Armstrong, 2007 ; Cheuvront & Kenefick, 2014 ; Cotter, Thornton, Lee, & Laursen, 2014 ). This is in part because dehydration is a complex condition that manifests as different types. When fluid

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Paola Rodriguez-Giustiniani and Stuart D.R. Galloway

as drink composition and volume ( Shirreffs & Maughan, 2000 ), but it is also believed that hormonal changes associated with the menstrual cycle can influence fluid retention ( Fortney, 1996 ). Although fluid replacement after dehydration has been extensively studied in males, there have been few

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Jason D. Vescovi and Greig Watson

accepted thresholds for dehydration and hypohydration, respectively. However, applying group-level data without knowing individual variation might not represent best practice. To date, only one study has examined the intraindividual variability of body mass and reported three consecutive days of morning

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Lawrence E. Armstrong, Jorge A. Herrera Soto, Frank T. Hacker Jr., Douglas J. Casa, Stavros A. Kavouras and Carl M. Maresh

This investigation evaluated the validity and sensitivity of urine color (Ucol), specific gravity (Usg), and osmolality (Uosm) as indices of hydration status, by comparing them to changes in body water. Nine highly trained males underwent a 42-hr protocol involving dehydration to 3.7% of body mass (Day 1, −2.64 kg), cycling to exhaustion (Day 2, −5.2% of body mass, −3.68 kg), and oral rehydration for 21 hr. The ranges of mean (across time) blood and urine values were Ucol, 1-7; Usg, 1.004-1.029; U08m, 117-1,081 mOsm • kg−1; and plasma osmolality (Posm), 280-298 mOsm ⋅ kg−1. Urine color tracked changes in body water as effectively as (or better than) Uosm, Usg, urine volume, Posm, plasma sodium, and plasma total protein. We concluded that (a) Ucol, Uosm, and Usg are valid indices of hydration status, and (b) marked dehydration, exercise, and rehydration had little effect on the validity and sensitivity of these indices.

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Robert G. Hahn and Nana Waldréus


Urine sampling has previously been evaluated for detecting dehydration in young male athletes. The present study investigated whether urine analysis can serve as a measure of dehydration in men and women of a wide age span.


Urine sampling and body weight measurement were undertaken before and after recreational physical exercise (median time: 90 min) in 57 volunteers age 17–69 years (mean age: 42). Urine analysis included urine color, osmolality, specific gravity, and creatinine.


The volunteers’ body weight decreased 1.1% (mean) while they exercised. There were strong correlations between all 4 urinary markers of dehydration (r = .73–.84, p < .001). Researchers constructed a composite dehydration index graded from 1 to 6 based on these markers. This index changed from 2.70 before exercising to 3.55 after exercising, which corresponded to dehydration of 1.0% as given by a preliminary reference curve based on 7 previous studies in athletes. Men were slightly dehydrated at baseline (mean: 1.9%) compared with women (mean: 0.7%; p < .001), though age had no influence on the results. A final reference curve that considered both the present results and the 7 previous studies was constructed in which exercise-induced weight loss (x) was predicted by the exponential equation x = 0.20 dehydration index1.86.


Urine sampling can be used to estimate weight loss due to dehydration in adults up to age 70. A robust dehydration index based on four indicators reduces the influence of confounders.

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Douglas J. Casa, Samuel N. Cheuvront, Stuart D. Galloway and Susan M. Shirreffs

extreme heat in which training and competition are likely to take place in Qatar, Tokyo, and other summer sporting venues of the future, the risks associated with dehydration could be amplified more than in previous years. This review focuses on the risks of dehydration and potential consequences to

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Dennis Passe, Mary Horn, John Stofan, Craig Horswill and Robert Murray

This study investigated the relationship between runners’ perceptions of fluid needs and drinking behavior under conditions of compensable heat stress (ambient temperature = 20.5 ± 0.7 °C, 68.9 °F; relative humidity = 76.6%). Eighteen experienced runners (15 men, 40.5 ± 2.5 y, and 3 women, 42 ± 2.3 y) were given ad libitum access to a sports drink (6% carbohydrate-electrolyte solution) at Miles 2, 4, 6, and 8. After the run (75.5 ± 8.0 min), subjects completed questionnaires that required them to estimate their individual fluid intake and sweat loss. Dehydration averaged 1.9% ± 0.8% of initial body weight (a mean sweat loss of 21.6 ± 5.1 mL·kg−1·h−1). Subjects replaced only 30.5% ± 18.1% of sweat loss and underestimated their sweat loss by 42.5% ± 36.6% (P ≤ 0.001). Subjects’ self-estimations of fluid intake (5.2 ± 3.2 mL·kg−1·h−1) were not significantly different from actual fluid intake (6.1 ± 3.4 mL·kg−1·h−1) and were significantly correlated (r = 0.63, P = 0.005). The data indicate that even under favorable conditions, experienced runners voluntarily dehydrate (P ≤ 0.001), possibly because they are unable to accurately estimate sweat loss and consequently cannot subjectively judge how much fluid to ingest to prevent dehydration. This conclusion suggests that runners should not depend on self-assessment to maintain adequate hydration, underscores the need for runners to enhance their ability to self-assess sweat losses, and suggests that a predetermined regimen of fluid ingestion might be necessary if they wish to maintain more optimal hydration.