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Daryll B. Bullen, Mary L. O'Toole and Karen C. Johnson

The purpose of this study was to compare daily calcium (Ca) losses in sweat (S) and urine (U) on an exercise day (E) with losses on the preceding day (i.e., a rest day) during which no exercise (NE) was performed. Ten healthy male volunteers (23.9 ± 3.2 years) performed a single bout of moderate exercise (running at 80% HRmax) for 45 min in a warm (32 °C, 58% relative humidity) environment on E. When E and NE were compared, neither Ca intake (1,232 ± 714 and 1,148 ±482 mg, respectively) nor urinary Ca excretion (206 ± 128 and 189 ± 130 mg, respectively) were different (p > .05). Sweat Ca losses during the exercise bout averaged 45 ± 12 mg. The results indicate that, although a small amount of Ca is lost in sweat during 45 min of moderate-intensity exercise, measured (sweat and urine losses combined) Ca losses (251 ±128 and 189 ± 130 mg) were not different (p > .05) between days (E and NE, respectively). These data suggest that moderate exercise for up to 45 min in a warm, humid environment does not markedly increase Ca intake requirements.

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Dirk Aerenhouts, Jelle Van Cauwenberg, Jacques Remi Poortmans, Ronald Hauspie and Peter Clarys

This study aimed to estimate nitrogen balance and protein requirements in adolescent sprint athletes as a function of growth rate and physical development. Sixty adolescent sprint athletes were followed up biannually over a 2-yr period. Individual growth curves and age at peak height velocity were determined. Skeletal muscle mass (SMM) was estimated based on anthropometric measurements and fat mass was estimated by underwater densitometry. Seven-day diet and physical activity diaries were completed to estimate energy balance and protein intake. Nitrogen analysis of 24-hr urine samples collected on 1 weekday and 1 weekend day allowed calculation of nitrogen balance. Body height, weight, and SMM increased throughout the study period in both genders. Mean protein intakes were between 1.4 and 1.6 g kg−1 day−1 in both genders. A protein intake of 1.46 g kg−1 day−1 in girls and 1.35 g kg−1 day−1 in boys was needed to yield a positive nitrogen balance. This did not differ between participants during and after their growth spurt. None of the growth parameters was significantly related to nitrogen balance. It can be concluded that a mean protein intake around 1.5 g kg−1 day−1 was sufficient to stay in a positive nitrogen balance, even during periods of peak growth. Therefore, protein intake should not be enhanced in peak periods of linear or muscular growth.

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J. Luke Pryor, Evan C. Johnson, Jeffery Del Favero, Andrew Monteleone, Lawrence E. Armstrong and Nancy R. Rodriguez

Postexercise protein and sodium supplementation may aid recovery and rehydration. Preserved beef provides protein and contains high quantities of sodium that may alter performance related variables in runners. The purpose of this study was to determine the effects of consuming a commercial beef product postexercise on sodium and water balance. A secondary objective was to characterize effects of the supplementation protocols on hydration, blood pressure, body mass, and running economy. Eight trained males (age = 22 ± 3 y, V̇O2max = 66.4 ± 4.2 ml·kg-1·min-1) completed three identical weeks of run training (6 run·wk-1, 45 ± 6 min·run-1, 74 ± 5% HRR). After exercise, subjects consumed either, a beef nutritional supplement (beef jerky; [B]), a standard recovery drink (SRD), or SRD+B in a randomized counterbalanced design. Hydration status was assessed via urinary biomarkers and body mass. No main effects of treatment were observed for 24 hr urine volume (SRD, 1.7 ± 0.5; B, 1.8 ± 0.6; SRD+B, 1.4 ± 0.4 L·d-1), urine specific gravity (1.016 ± 0.005, 1.018 ± 0.006, 1.017 ± 0.006) or body mass (68.4 ± 8.2, 68.3 ± 7.7, 68.2 ± 8.1 kg). No main effect of treatment existed for sodium intake—loss (-713 ± 1486; -973 ± 1123; -980 ± 1220 mg·d-1). Mean arterial pressure (81.0 ± 4.6, 81.1 ± 7.3, 83.8 ± 5.4 mm Hg) and average exercise running economy (V̇O2: SRD, 47.9 ± 3.2; B, 47.2 ± 2.6; SRD+B, 46.2 ± 3.4 ml·kg-1·min-1) was not affected. Urinary sodium excretion accounted for the daily sodium intake due to the beef nutritional supplement. Findings suggest the commercial beef snack is a viable recovery supplement following endurance exercise without concern for hydration status, performance decrements, or cardiovascular consequences.

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Rebekah D. Alcock, Gregory C. Shaw, Nicolin Tee, Marijke Welvaert and Louise M. Burke

bottles (2 L capacity) for a period of 24 hr, divided into three collection periods ( t  = 0–6, 6–12, and 12–24 hr). The subjects also completed 24-hr urine collections on 2 BL days when no supplement was consumed, and their normal eating patterns were maintained using breakfast as t  = 0 and continuing

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D. Enette Larson-Meyer, Kathleen Woolf and Louise Burke

, turnip and mustard greens, soy milk, black strap molasses, calcium-fortified juices Common measure: no appropriate indicator of calcium status; 24-hr urine somewhat responsive to changes in dietary calcium; calcium in overnight urine ample indicator of compliance with calcium supplement n – Physical

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Eric Kyle O’Neal, Samantha Louise Johnson, Brett Alan Davis, Veronika Pribyslavska and Mary Caitlin Stevenson-Wilcoxson

criterion. In addition to the influence of reduced total body water loss from exercise, it is plausible that preexercise hypohydration or hyperhydration may also potentially explain a significant portion of the assessment errors. Armstrong et al. ( 2010 ) found less than 2% of USG from 24-hr urine

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Kirsty J. Elliott-Sale, Adam S. Tenforde, Allyson L. Parziale, Bryan Holtzman and Kathryn E. Ackerman

release and attenuating pituitary LH pulsatility in animals ( Martin et al., 2008 ). Loucks et al. ( 1989 ) showed no differences in ACTH secretion or cortisol pulse frequency in amenorrheic athletes versus eumenorrheic athletes or controls, but 24-hr urine cortisol measurements were higher in the