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Kevin Tipton, Nancy R. Green, Emily M. Haymes, and Mary Waller

Zinc (Zn) loss from sweat of 9 male and 9 female athletes exercising under hot (35°C, HE) and neutral (25°C, ME) conditions was examined. Subjects exercised at 50% VO2max on a cycle ergometer for 1 hr during each trial. Cell-free sweat samples were analyzed for Zn by atomic absorption spectro-photometry. There was a significant interaction of time, gender, and temperature for whole-body sweat rates (WBSR). WBSR for males were higher during both trials and at each time. WBSR from the second half of exercise were higher than those from the first half for both sexes and temperature conditions. Sweat Zn concentration was higher in the NE than in the HE, but when the sweat rates were included, the rate of Zn loss was no different between HE and NE. Zn concentration of the sweat for the first half of exercise was over twice that of the second half. Sweat Zn concentration of the men was no different than that of the women; however, due to greater sweat rate, men had significantly higher Zn losses. Although total Zn losses are estimated to be relatively low compared to the RDA. exercise at moderate intensities may increase surface Zn losses.

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Kevin C. Miller, Brendon P. McDermott, and Susan W. Yeargin

and electrolyte losses are the most popular assumed causative factors ( Stone et al., 2003 ). The dehydration/electrolyte theory states that sweating contracts the extracellular fluid space increasing the concentration of excitatory neurochemicals and mechanical pressure on motor nerve terminals

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Anita M. Rivera-Brown and José R. Quiñones-González

Athletes are advised to maintain proper fluid intake during training and competition in order to avoid the adverse effects of dehydration and hyponatremia. However, many athletes are unaware of the amount of fluid they lose in sweat and the implications of inadequate fluid intake when sweat losses

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Steve H. Faulkner, Iris Broekhuijzen, Margherita Raccuglia, Maarten Hupperets, Simon G. Hodder, and George Havenith

with no performance feedback other than the accumulated work done, target workload, and a graphical representation of fluctuations in power output. Participants were allowed to drink water ad libitum, with the total volume consumed recorded to allow for calculation of sweat loss. During the warm-up and

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Lindsay B. Baker, Kelly A. Barnes, Bridget C. Sopeña, Ryan P. Nuccio, Adam J. Reimel, and Corey T. Ungaro

The collection of athletes’ sweat during training or competition is a common practice in sports science. Sodium ([Na + ]), potassium ([K + ]), and/or chloride ([Cl − ]) concentrations are measured to estimate athletes’ sweat electrolyte losses to determine electrolyte balance or inform personalized

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Coen C.W.G. Bongers, Dominique S.M. ten Haaf, Nicholas Ravanelli, Thijs M.H. Eijsvogels, and Maria T.E. Hopman

develop heat-related illnesses. 2 Sweating is the largest modifiable heat loss avenue to mitigate the rise in CBT. Previous studies have proposed that sex independently alters the CBT and sweating response to exercise 3 ; however, it may simply be a result of morphological characteristics and heat

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Ronald J. Maughan and Susan M. Shirreffs

Athletes are encouraged to begin exercise well hydrated and to consume sufficient amounts of appropriate fluids during exercise to limit water and salt deficits. Available evidence suggests that many athletes begin exercise already dehydrated to some degree, and although most fail to drink enough to match sweat losses, some drink too much and a few develop hyponatremia. Some simple advice can help athletes assess their hydration status and develop a personalized hydration strategy that takes account of exercise, environment, and individual needs. Preexercise hydration status can be assessed from urine frequency and volume, with additional information from urine color, specific gravity, or osmolality. Change in hydration during exercise can be estimated from the change in body mass that occurs during a bout of exercise. Sweat rate can be estimated if fluid intake and urinary losses are also measured. Sweat salt losses can be determined by collection and analysis of sweat samples, but athletes losing large amounts of salt are likely to be aware of the taste of salt in sweat and the development of salt crusts on skin and clothing where sweat has evaporated. An appropriate drinking strategy will take account of preexercise hydration status and of fluid, electrolyte, and substrate needs before, during, and after a period of exercise. Strategies will vary greatly between individuals and will also be influenced by environmental conditions, competition regulations, and other factors.

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Alexander S.D. Gamble, Jessica L. Bigg, Tyler F. Vermeulen, Stephanie M. Boville, Greg S. Eskedjian, Sebastian Jannas-Vela, Jamie Whitfield, Matthew S. Palmer, and Lawrence L. Spriet

∼2% of their body mass (BM) through sweating ( Baker et al., 2007 ; Dougherty et al., 2006 ; Edwards et al., 2007 ; Linseman et al., 2014 ; McGregor et al., 1999 ; Owen et al., 2013 ; Palmer et al., 2017 ). The equipment worn by ice hockey players becomes problematic as sweat rates increase to

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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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Jason P. Brandenburg and Michael Gaetz

This study determined the fluid balance of elite female basketball players before and during competition. Before and during 2 international games, 17 national-level players (age 24.2 ± 3 yr, height 180.5 ± 6 cm, mass 78.8 ± 8 kg) were assessed. Fluid-balance assessment included pregame hydration level as determined by urine specific gravity (USG), change in body mass during the game, ad libitum intake of water or sports drink, and estimated sweat losses. Mean (± SD) USG before Game 1 was 1.005 ± 0.002 and before Game 2 USG equaled 1.010 ± 0.005. Players lost an average of 0.7% ± 0.8% and 0.6% ± 0.6% of their body mass during Games 1 and 2, respectively. In each game, 3 players experienced a fluid deficit >1% of body mass, and 1 other, a fluid deficit >2%. Sweat losses in both games, from the beginning of the warm-up to the conclusion of the game (~125 min with average playing time 16–17 min), were approximately 1.99 ± 0.75 L. Fluid intake in Game 1 and Game 2 equaled 77.8% ± 32% and 78.0% ± 21% of sweat losses, respectively. Most players were hydrated before each game and did not become meaningfully dehydrated during the game. It is possible that the players who experienced the highest levels of dehydration also experienced some degree of playing impairment, and the negative relationship between change in body mass and shooting percentage in Game 2 provides some support for this notion.