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Lawrence E. Armstrong, Carl M. Maresh, John W. Castellani, Michael F. Bergeron, Robert W. Kenefick, Kent E. LaGasse and Deborah Riebe

Athletes and researchers could benefit from a simple and universally accepted technique to determine whether humans are well-hydrated, euhydrated, or hypohydrated. Two laboratory studies (A, B) and one field study (C) were conducted to determine if urine color (Ucol) indicates hydration status accurately and to clarify the interchangeability of Ucol, urine osmolality (Uosm), and urine specific gravity (Usg) in research. Ucol, Uosm, and Usg were not significantly correlated with plasma osmolality, plasma sodium, or hemato-crit. This suggested that these hematologic measurements are not as sensitive to mild hypohydration (between days) as the selected urinary indices are. When the data from A, B, and C were combined, Ucol was strongly correlated with Uhg and U„sm. It was concluded that (a) Ucol may be used in athletic/industrial settings or field studies, where close estimates of Usg or Uosm are acceptable, but should not be utilized in laboratories where greater precision and accuracy are required, and (b) Uosm and Usg may be used interchangeably to determine hydration status.

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Sareen S. Gropper, L. Michelle Sorrels and Daniel Blessing

Copper status was assessed in 70 female collegiate athletes aged 18 to 25 years participating in cross country track, tennis, softball, swimming, soccer, basketball, and gymnastics during the 2000–2001 season. A group of 8 college-aged females, 20 to 23 years of age, who were not collegiate athletes, served as controls. Mean copper intakes including supplements did not differ significantly among the controls and athletic teams. Mean copper intakes including supplements as micrograms/day and percent recommended dietary allowance (RDA) were as follows: controls 1071 ± 772 μg (119 ± 86%), cross country track 1468 ± 851 μg (163 ± 95%), tennis 1099 ± 856 μg (122 ± 95%), softball 654 ± 420 μg (73 ± 47%), swimming 1351 ± 1060 μg (150 ± 118%), soccer 695 ± 368 μg (77 ± 41%), and gymnastics 940 ± 863 μg (104 ± 96%). Forty-one percent of athletes and 29% of controls failed to consume two thirds of the RDA for copper. Mean serum copper and ceruloplasmin concentrations were within the normal range and did not differ significantly among the controls (117 ± 22 μg/dl, 445 ± 122 μg/L) and cross country track (98 ± 17 μg/dl, 312 ± 59 μg/L), tennis (140 ± 84 μg/dl, 424 ± 244 μg/L), softball (95 ± 30 μg/dl, 310 ± 77 μg/L), swimming (98 ± 25 μg/dl, 312 ± 40 μg/L), soccer (93 ± 15 μg/dl, 324 ± 54 μg/ L), basketball (85 ± 10 μg/dl, 280 ± 62 μg/L), and gymnastics (96 ± 21 μg/dl, 315 ± 68 μg/L) teams. Copper status of female collegiate athletes appears to be adequate in this cross-sectional assessment.

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Noreen D. Willows, Susan K. Grimston, Delia Roberts, David J. Smith and David A. Hanley

This study assessed serum ferritin, hemoglobin, and hematocrit among 107 physically active young people 9 to 18 years of age. Tanner stage (TS) of puberty was assessed and subjects were categorized as prepubertal (TS 1), midpubertal (TS 2, 3, and 4, excluding menarcheal females) and going through their rapid growth phase, or late pubertal (TS 5 and menarcheal females) and having completed their rapid growth phase. Midpubertal females had a lower hematocrit than late pubertal females, but there were no significant differences in serum ferritin or hemoglobin between pubertal groups. Late pubertal males had hemoglobin and hematocrit values that were higher than among prepubertal males, but serum ferritin did not differ. At late puberty the males had significantly higher serum ferritin, hemoglobin, and hematocrit compared with late pubertal females, and females in late puberty were more likely to have marginal iron stores compared with males at the same stage of pubertal development. Midpubertal and late pubertal females reported a diet low in absorbed iron, which could contribute to their poorer iron status.

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Noreen D. Willows, Susan K. Grimston, David J. Smith and David A. Hanley

This study assessed change in hematological status among physically active children as they progressed through puberty. Values for serum ferritin, hemoglobin, and hematocrit at all stages of puberty were within the normal range of reference values. Significant changes in serum ferritin were not detected in the different pubertal stages, although serum ferritin was highest in prepubertal boys and girls. There were no significant differences in marginal or deficient iron stores between the sexes at any pubertal stage, suggesting that gender was not predisposing for iron deficiency; however, girls had a greater overall incidence for both measures. With more children under consideration, these trends may have reached significance. Boys in TS4 and TS5 had higher hemoglobin and hematocrit compared with earlier stages of puberty, and compared with girls at the same stages of puberty. This can be explained by testosterone production in boys. Among girls, pubertal progression had no significant effect on hemoglobin or hematocrit. In the absence of controls, there was no direct evidence that involvement in sports had an adverse effect on iron status.

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Abderraouf Ben Abderrahman, Jacques Prioux, Karim Chamari, Omar Ben Ounis, Zouhair Tabka and Hassane Zouhal

The effect of endurance interval training (IT) on hematocrit (Ht), hemoglobin (Hb), and estimated plasma-volume variation (PVV) in response to maximal exercise was studied in 15 male subjects (21.1 ± 1.1 y; control group n = 6, and training group, n = 9). The training group participated in interval training 3 times a week for 7 wk. A maximal graded test (GXT) was performed to determine maximal aerobic power (MAP) and maximal aerobic speed (MAS) both before and after the training program. To determine Ht, Hb concentration, and lactate concentrations, blood was collected at rest, at the end of GXT, and after 10 and 30 min of recovery. MAP and MAS increased significantly (P < .05) after training only in training group. Hematocrit determined at rest was significantly lower in the training group than in the control group after the training period (P < .05). IT induced a significant increase of estimated PVV at rest for training group (P < .05), whereas there were no changes for control group. Hence, significant relationships were observed after training between PVV determined at the end of the maximal test and MAS (r = .60, P < .05) and MAP (r = .76, P < .05) only for training group. In conclusion, 7 wk of IT led to a significant increase in plasma volume that possibly contributed to the observed increase of aerobic fitness (MAP and MAS).

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John S. Cuddy, Dustin R. Slivka, Walter S. Hailes, Charles L. Dumke and Brent C. Ruby

Purpose:

The purpose of this study was to determine the metabolic profile during the 2006 Ironman World Championship in Kailua-Kona, Hawaii.

Methods:

One recreational male triathlete completed the race in 10:40:16. Before the race, linear regression models were established from both laboratory and feld measures to estimate energy expenditure and substrate utilization. The subject was provided with an oral dose of 2H2 18O approximately 64 h before the race to calculate total energy expenditure (TEE) and water turnover with the doubly labeled water (DLW) technique. Body weight, blood sodium and hematocrit, and muscle glycogen (via muscle biopsy) were analyzed pre- and postrace.

Results:

The TEE from DLW and indirect calorimetry was similar: 37.3 MJ (8,926 kcal) and 37.8 MJ (9,029 kcal), respectively. Total body water turnover was 16.6 L, and body weight decreased 5.9 kg. Hematocrit increased from 46 to 51% PCV. Muscle glycogen decreased from 152 to 48 mmoL/kg wet weight pre- to postrace.

Conclusion:

These data demonstrate the unique physiological demands of the Ironman World Championship and should be considered by athletes and coaches to prepare sufficient nutritional and hydration plans.

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João C. Dias, Melissa W. Roti, Amy C. Pumerantz, Greig Watson, Daniel A. Judelson, Douglas J. Casa and Lawrence E. Armstrong

Context:

Dieticians, physiologists, athletic trainers, and physicians have recommended refraining from caffeine intake when exercising because of possible fluid-electrolyte imbalances and dehydration.

Objective:

To assess how 16-hour rehydration is affected by caffeine ingestion.

Design:

Dose–response.

Setting:

Environmental chamber.

Participants:

59 college-age men.

Intervention:

Subjects consumed a chronic caffeine dose of 0 (placebo), 3, or 6 mg · kg−1 · day−1 and performed an exercise heat-tolerance test (EHT) consisting of 90 minutes of walking on a treadmill (5.6 km/h) in the heat (37.7 °C).

Outcome Measures:

Fluid-electrolyte measures.

Results:

There were no between-group differences immediately after and 16 hours after EHT in total plasma protein, hematocrit, urine osmolality, specific gravity, color, and volume. Body weights after EHT and the following day (16 hours) were not different between groups (P > .05).

Conclusion:

Hydration status 16 hours after EHT did not change with chronic caffeine ingestion.

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Richard Frazee, Denis Brunt and Robert F. Castle

This paper describes the exercise tolerance of a young girl with a congenital heart defect associated with asplenia syndrome. The child was exercised minimally on a treadmill for a period of 10 minutes, during which time heart rate, blood pressure, ECG, and transcutaneous PO2 values were monitored. Due to a small increase in heart rate and a very low PO2 during exercise, it was suggested that some adaptive mechanism had been developed to counteract her cyanotic condition. An optimal increase in hematocrit and hemoglobin levels supported this. No ECG abnormalities were noted. It was concluded that this child should have some, but minimal, involvement in physical education programs despite the severity of her condition.

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Manuel Lugo, William M. Sherman, Gregory S. Wimer and Keith Garleb

This study examined the effects of consuming the same amount of carbohydrate in solid form, liquid form, or both on metabolic responses during 2 hrs of cycling at 70% peak VO2 and on cycling time-trial performance. Subjects consumed 0.4 g carbohydrate/kg body mass before and every 30 min during exercise. The liquid was a 7% carbohydrate-electrolyte beverage and the solid was a sports bar (1171 kJ) in which 76%, 18%, and 6% of total energy was derived from carbohydrate, fat, and protein, respectively. Blood obtained at baseline, before exercise, and every 30 min was analyzed for glucose, insulin, lactate, hemoglobin, hematocrit, and plasma volume. There were no differences among the treatments for the blood parameters. Total carbohydrate oxidation and time-trial performance were also similar among treatments. Under thermoneutral conditions with equal liquid inges-tion, the metabolic and performance responses are similar when consuming carbohydrate as a liquid, solid, or in combination during prolonged, moderate intensity cycling.

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Beat Knechtle, Patrizia Knechtle and Thomas Rosemann

Purpose:

Fluid overload is considered a main risk factor for exercise-associated hyponatremia (EAH). The aim of this study was to investigate the incidence of EAH in ultra-runners at the 100 km ultra-run in Biel, Switzerland.

Methods:

Pre- and postrace, body mass, urinary specific gravity, hemoglobin, hematocrit, plasma [Na+], and plasma volume were determined.

Results:

Of the 145 finishers, seven runners (4.8%) developed asymptomatic EAH. While running, the athletes consumed a total of (median and interquartile ranges) 6.9 (5.1-8.8) L over the 100 km distance, equal to 0.58 (0.41-0.79) L/h. Fluid intake correlated negatively and significantly with race time (r = -.50, P < .0001). Body mass decreased, plasma [Na+] remained unchanged, hematocrit and hemoglobin decreased, and urinary specific gravity increased. Plasma volume increased by 4.6 (-2.3 to 12.8) %. Change in body mass correlated with both postrace plasma [Na+] and Δ plasma [Na+]. Postrace plasma [Na+] correlated to Δ plasma [Na+]. Fluid intake was associated neither with postrace plasma [Na+] nor with Δ plasma [Na+]. Fluid intake was related to Δ body mass (r = .21, P = .012), but not to postrace body mass. Fluid intake showed no correlation to Δ plasma volume. Change in plasma volume was associated with postrace [Na+].

Conclusions:

Incidences of EAH in 100 km ultra-marathoners were lower compared with reports on marathoners. Body mass decreased, plasma volume increased, and plasma [Na+] was maintained. Since fluid intake was related neither to Δ plasma volume nor to Δ plasma [Na+], we assume that factors other than fluid intake maintained body fluid homeostasis.