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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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Martin J. Barwood, Joe Kupusarevic, and Stuart Goodall

(Physicool™, London, UK), has been reliably shown to induce improvements in TS and comfort, during fixed intensity (FI) 11 and self-paced exercise 3 , 8 , 9 in the heat. However, it has also been shown to induce heat gain responses (ie, vasoconstriction 11 ) and alter sweating responses, 12 in the latter

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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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Matthew Zimmermann, Grant Landers, Karen Wallman, and Georgina Kent

neural drive, 4 , 5 and impaired energy efficiency. 6 , 7 A critical core temperature of 39.5°C to 40°C has also been reported to result in premature fatigue. 1 , 4 Furthermore, although excessive sweating during exercise in the heat is effective at cooling the body, it results in an earlier onset of

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Ronald J. Maughan, Lisa A. Dargavel, Rachael Hares, and Susan M. Shirreffs

This study investigated fluid and electrolyte balance in well-trained male and female swimmers during 2 training sessions. Participants were 17 nationally ranked swimmers measured during a period of intensive training. Sweat loss was assessed from changes in body mass after correction for fluid intake and urine collection. Sweat composition was measured from waterproof absorbent patches applied at 4 skin sites. Air and pool-water temperatures were 36 °C and 27.4 °C, respectively. Training lasted 105 min in each session. All measured variables were similar on the 2 testing days. Mean sweat-volume loss was 548 ± 243 ml, and mean sweat rate was 0.31 ± 0.1 L/hr. Mean fluid intake was 489 ± 270 ml. Mean body-mass loss was 0.10 ± 0.50 kg, equivalent to 0.1% ± 0.7% dehydration. Mean pretraining urine osmolality was 662 ± 222 mOsm/kg, which was negatively associated with both mean drink volume consumed (p = .044, r 2 = .244) and mean urine volume produced during training (p = .002, r 2 = .468). Mean sweat Na+, K+, and Cl concentrations (mmol/L) were 43 ± 14, 4 ± 1, and 31± 9, respectively; values were not different between males and females and were not different between days except for a marginal difference in K+ concentration. The average swimmer remained hydrated during the session, and calculated sweat rates were similar to those in previous aquatic studies.

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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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Matthew Zimmermann, Grant Landers, Karen E. Wallman, and Jacinta Saldaris

This study examined the physiological effects of crushed ice ingestion before steady state exercise in the heat. Ten healthy males with age (23 ± 3 y), height (176.9 ± 8.7 cm), body-mass (73.5 ± 8.0 kg), VO2peak (48.5 ± 3.6 mL∙kg∙min-1) participated in the study. Participants completed 60 min of cycling at 55% of their VO2peak preceded by 30 min of precooling whereby 7 g∙kg-1 of thermoneutral water (CON) or crushed ice (ICE) was ingested. The reduction in Tc at the conclusion of precooling was greater in ICE (-0.9 ± 0.3 °C) compared with CON (-0.2 ± 0.2 °C) (p ≤ .05). Heat storage capacity was greater in ICE compared with CON after precooling (ICE -29.3 ± 4.8 W∙m-2; CON -11.1 ± 7.3 W∙m-2, p < .05). Total heat storage was greater in ICE compared with CON at the end of the steady state cycle (ICE 62.0 ± 12.5 W∙m-2; CON 49.9 ± 13.4 W∙m-2, p < .05). Gross efficiency was higher in ICE compared with CON throughout the steady state cycle (ICE 21.4 ± 1.8%; CON 20.4 ± 1.9%, p < .05). Ice ingestion resulted in a lower thermal sensation at the end of precooling and a lower sweat rate during the initial stages of cycling (p < .05). Sweat loss, respiratory exchange ratio, heart rate and ratings of perceived exertion and thirst were similar between conditions (p > .05). Precooling with crushed ice led to improved gross efficiency while cycling due to an increased heat storage capacity, which was the result of a lower core temperature.

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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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Ronald J. Maughan, Stuart J. Merson, Nick P. Broad, and Susan M. Shirreffs

This study measured fluid balance during a 90-min preseason training session in the first team squad (24 players) of an English Premier League football team. Sweat loss was assessed from changes in body mass after correction for ingested fluids and urine passed. Sweat composition was measured by collection from patches attached to the skin at 4 sites. The weather was warm (24-29 °C), with moderate humidity (46–64%). The mean ± SD body mass loss over the training session was 1.10 ± 0.43 kg, equivalent to a level of dehydration of 1.37 ± 0.54% of the pre-training body mass. Mean fluid intake was 971 ± 303 ml. Estimated total mean sweat loss was 2033 ±413 ml. Mean sweat electrolyte concentrations (mmol/L) were: sodium,49± 12; potassium,6.0± 1.3;chloride, 43 ± 10. Total sweat sodium loss of 99 ± 24 mmol corresponds to a salt (sodium chloride) loss of 5.8 ± 1.4 g. Mean urine osmolality measured on pre-training samples provided by the players was 666 ±311 mosmol/kg (n=21). These data indicate that sweat losses of water and solute in football players in training can be substantial but vary greatly between players even with the same exercise and environmental conditions. Voluntary fluid intake also shows wide inter-individual variability and is generally insufficient to match fluid losses.