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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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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.

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Dennis H. Passe, Mary Horn, John Stofan and Robert Murray

Palatability and voluntary intake of 4 beverages commonly available to athletes were compared in a laboratory exercise protocol designed to mimic aerobic training or competitive conditions in which limited time is available for drinking. Diluted orange juice (DOJ), homemade 6% carbohydrate-electrolyte sports beverage (HCE), commercially available 6% carbohydrate-electrolyte sports beverage (CCE), and water (W) were tested. Fifty adult triathletes and runners (34 males, 16 females) exercised for 75 min at 80–85% of age-predicted heart rate, during which time they were given brief access (60 s) to one of the beverages after 30 min and 60 min of exercise. Results indicated that for overall palatability, CCE > W, HCE, DOJ; W > DOJ, and for amount of beverage consumed, CCE > W, HCE, DOJ; HCE > W, DOJ. The palatability of these beverages varied substantially, as did their voluntary intakes during exercise.

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Robert Murray, William Bartoli, John Stofan, Mary Horn and Dennis Eddy

The purpose of this study was to determine the effects of repeated ingestion of drinks containing varying concentrations of carbohydrate on gastric emptying rate during steady-state exercise. On five separate occasions, 14 subjects cycled for 90 min at an average power output of 151 ± 2 W. At 15-min intervals, subjects ingested 227 ± 3 ml of either water, 4% carbohydrate (CHO), 6% CHO, or 8% CHO. Gastric volume was determined prior to each drink and at 90 min using the modified double-sampling technique. Gross gastric volumes were significantly greater and mean gastric emptying rates and the percentage of ingested beverage emptied from the stomach were significantly less for 8% CHO. These data indicate that repeated ingestion of an 8% CHO beverage during exercise significantly reduces gastric emptying rate, whereas lower concentrations of carbohydrate do not. In addition, beverage osmolality is not as important as beverage energy content in influencing gastric emptying rate at these carbohydrate concentrations.

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Lindsay B. Baker, John R. Stofan, Henry C. Lukaski and Craig A. Horswill

Simultaneous whole-body wash-down (WBW) and regional skin surface sweat collections were completed to compare regional patch and WBW sweat calcium (Ca), magnesium (Mg), copper (Cu), manganese (Mn), iron (Fe), and zinc (Zn) concentrations. Athletes (4 men, 4 women) cycled in a plastic open-air chamber for 90 min in the heat. Before exercise, the subjects and cycle ergometer (covered in plastic) were washed with deionized water. After the onset of sweating, sterile patches were attached to the forearm, back, chest, forehead, and thigh and removed on saturation. After exercise, the subjects and cycle ergometer were washed with 5 L of 15-mM ammonium sulfate solution to collect all sweat minerals and determine the volume of unevaporated sweat. Control trials were performed to measure mineral contamination in regional and WBW methods. Because background contamination in the collection system was high for WBW Mn, Fe, and Zn, method comparisons were not made for these minerals. After correction for minimal background contamination, WBW sweat [Ca], [Mg], and [Cu] were 44.6 ± 20.0, 9.8 ± 4.8, and 0.125 ± 0.069 mg/L, respectively, and 5-site regional (weighted for local sweat rate and body surface area) sweat [Ca], [Mg], and [Cu] were 59.0 ± 15.9, 14.5 ± 4.8, and 0.166 ± 0.031 mg/L, respectively. Five-site regional [Ca], [Mg], and [Cu] overestimated WBW by 32%, 48%, and 33%, respectively. No individual regional patch site or 5-site regional was significantly correlated with WBW sweat [Ca] (r = –.21, p = .65), [Mg] (r = .49, p = .33), or [Cu] (r = .17, p = .74). In conclusion, regional sweat [Ca], [Mg], and [Cu] are not accurate surrogates for or significantly correlated with WBW sweat composition.

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Craig A. Horswill, Dave G. Curby, William P. Bartoli, John R. Stofan and Robert Murray

We examined whether the type of fluid ingested during wrestling training would affect arm ergometry in adolescent athletes. Wrestlers (n = 11) trained for 2-hr sessions and consumed fluid containing 6% carbohydrate or a placebo of equal volume administered double blind and in randomized fashion. To account for training demands across beverage comparisons, energy expenditure (EE) was estimated by using the rate of appearance of CO2 (RaCO2) after 13C-bicarbonate ingestion. The performance test was completed after training and consisted of 6 min of intermittent, high-intensity arm cranking. The results showed the difference in total arm work (kg • m−2 • min) between carbohydrate (2,130 ± 263) and placebo (1,961 ± 401) conditions approached statistical significance (p = .07). Fluid intake matched 50% of sweat loss, resulting in modest dehydration for both treatments. Carbohydrate ingestion during training may enhance high-intensity intermittent arm work in adolescent wrestlers; however, the additive effects of carbohydrate dose and fluid volume for hydration need to be teased apart in subsequent research on adolescents performing such exercise.

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Craig A. Horswill, Dennis H. Passe, John R. Stofan, Mary K. Horn and Robert Murray

We compared ad libitum fluid consumption in adolescent (n = 15) and adult athletes (n = 34) exercising in similar environmental conditions (26.5°C, 27.3% relative humidity) and similar modes and intensities of exercise (80-85% of their age-predicted maximum heart rate). Throughout 1 hr of exercise, participants had access to sports bottles containing a sports drink (6% carbohydrate with electrolytes and identical flavoring). Sweat rate (SR) and percent dehydration were calculated from the change in body weight corrected for urine loss and fluid intake (FI). FI was significantly higher for the adults than for the adolescents. SR was also higher for the adults compared with that of the adolescents. Compared with adults, adolescents had significantly lower FI and SR, the combination of which allowed them to meet their fluid needs more closely during exercise. Minimal voluntary dehydration occurred in either group during exercise, possibly because of the nature of the exercise (noncompetitive) or the beverage characteristics (presence of sodium and sweetness) or availability of the beverage.

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John R. Stofan, Kris L. Osterberg, Craig A. Horswill, Magie Lacambra, E. Randy Eichner, Scott A. Anderson and Robert Murray

The authors measured 24-h fluid-turnover (FTO) rate during 6 d of preseason training in U.S. college football players. Players, training (T, n = 9, full gear and contact drills) and reference (R, n = 4, conditioning without gear or contact), ingested a deuterium oxide (D2O) dose and provided urine samples every 24 h for analysis of D2O. During one ~2.3–h practice (wet-bulb globe temperature 24.6 °C), body-mass change, urine production, and voluntary fluid intake were measured to calculate gross sweat loss (GSL). Average FTO was 10.3 ± 2.2 L/d for T and 7.0 ± 1.0 L/d for R. GSL was 3.4 ± 1.5 L for T and 1.7 ± 1.3 for R (P > 0.05). By Day 6, body mass decreased significantly in T (–2.4 ± 1.3 kg, P < 0.05) but not in R (0.38 ± 0.95 kg). With preseason training under moderate environmental stress, football players had high FTO and sweat rates, which might have contributed to a loss of body mass during preseason football training.

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John R. Stofan, Jeffrey J. Zachwieja, Craig A. Horswill, Robert Murray, Scott A. Anderson and E. Randy Eichner

This observational study was designed to determine whether football players with a history of heat cramps have elevated fluid and sodium losses during training. During a “two-a-day” training camp, five Division I collegiate football players (20.2 ± 1.6 y, 113 ± 20 kg) with history of heat cramps (C) were matched (weight, age, race and position) with a cohort of teammates (19.6 ± 0.6 y, 110 ± 20 kg) who had never cramped (NC). Change in body weight (adjusted by fluid intake) determined gross sweat loss. Sweat samples (forearm patch) were analyzed for sodium and potassium concentrations. Adlibitum fluid intake was measured by recording pre- and post-practice bottle weights. Average sweat sodium loss for a 2.5-h practice was projected at 5.1 ± 2.3 g (C) vs. 2.2 ± 1.7 g (NC). When averaged across two practices within the day, fluid intake was similar between groups (C: 2.6 ± 0.8 L vs. NC: 2.8 ± 0.7 L), as was gross sweat loss (C: 4.0 ± 1.1 L vs. NC: 3.5 ± 1.6 L). There was wide variability in the fluid deficit incurred for both C and NC (1.3 ± 0.9 vs. 0.7 ± 1.2%) due to fluid intake. Sweat potassium was similar between groups, but sweat sodium was two times higher in C versus NC (54.6 ± 16.2 vs. 25.3 ± 10.0 mmol/L). These data indicate that sweat sodium losses were comparatively larger in cramp-prone football players than in NC. Although both groups consumed sodium-containing fluids (on-field) and food (off-field), both appeared to experience an acute sodium deficit at the end of practices based on sweat sodium losses. Large acute sodium and fluid losses (in sweat) may be characteristic of football players with a history of heat cramping.

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Xiaocai Shi, Mary K. Horn, Kris L. Osterberg, John R. Stofan,, Jeffrey J. Zachwieja, Craig A. Horswill, Dennis H. Passe and Robert Murray

This study investigated whether different beverage carbohydrate concentration and osmolality would provoke gastrointestinal (GI) discomfort during intermittent, high-intensity exercise. Thirty-six adult and adolescent athletes were tested on separate days in a double-blind, randomized trial of 6% and 8% carbohydrate-electrolytes (CHO-E) beverages during four 12-min quarters (Q) of circuit training that included intermittent sprints, lateral hops, shuttle runs, and vertical jumps. GI discomfort and fatigue surveys were completed before the first Q and immediately after each Q. All ratings of GI discomfort were modest throughout the study. The cumulative index for GI discomfort, however, was greater for the 8% CHO-E beverage than for the 6% CHO-E beverage at Q3 and Q4 (P < 0.05). Averaging across all 4 quarters, the 8% CHO-E treatment produced significantly higher mean ratings of stomach upset and side ache. In conclusion, higher CHO concentration and osmolality in an ingested beverage provokes stomach upset and side ache.