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Alannah K.A. McKay, Rachel McCormick, Nicolin Tee, and Peter Peeling

. One theme that has yet to be sufficiently studied, however, is the impact of heat exposure on the iron regulatory response to exercise. Relevant to heat stress, it is known that the gastrointestinal tract becomes increasingly permeable with an increased thermal load, resulting in the release of

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Ed Maunder, Daniel J. Plews, Fabrice Merien, and Andrew E. Kilding

temperate and hot environments. 5 Heat stress increases heart rate at a given pace/power, 6 and lowers the pace/power achieved at individual physiological thresholds. 7 However, it is not known if heart rates at the physiological thresholds measured in a temperate environment are reflective of heart

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Ed Maunder, Andrew E. Kilding, Christopher J. Stevens, and Daniel J. Plews

A common practice among endurance athletes is to train in hot environments for several weeks during a “heat stress camp,” with the intention of augmenting physiological stress and therefore metabolic adaptations to training. 1 Despite its widespread use, the effectiveness of combined exercise-heat

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Fergus K. O’Connor, Steven E. Stern, Thomas M. Doering, Geoffrey M. Minett, Peter R. Reaburn, Jonathan D. Bartlett, and Vernon G. Coffey

radiation (SR) exposure together with constant T a and RH elevates T sk , reduces the core-to-skin temperature gradient, and subsequently leading to decreased endurance capacity. Accordingly, each heat stress variable contributing to total heat strain may have individual effects with the potential to

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Michael J. Zurawlew, Jessica A. Mee, and Neil P. Walsh

Prior to exercise-heat stress, athletes and military personnel are advised to complete a period of heat acclimation to alleviate heat strain and improve exercise capacity in the heat. 1 The adaptive responses that improve exercise capacity in the heat include an earlier onset and an increase in

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Ben J. Lee, Tessa R. Flood, Ania M. Hiles, Ella F. Walker, Lucy E.V. Wheeler, Kimberly M. Ashdown, Mark E.T. Willems, Rianne Costello, Luke D. Greisler, Phebe A. Romano, Garrett W. Hill, and Matthew R. Kuennen

anthocyanin-rich berry extracts could therefore be a viable strategy to mitigate against exertional heat stress–induced GI barrier damage. Blackcurrants ( Ribes nigrum L. ) contain appreciable amounts of anthocyanins (∼585 mg/100 g), including primarily cyanidin-3-O-glucoside, cyanidin-3-O

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Maria Misailidi, Konstantinos Mantzios, Christos Papakonstantinou, Leonidas G. Ioannou, and Andreas D. Flouris

. Heat stress, hydration, and heat illness in elite tennis players . In: Di Giacomo G , Ellenbecker TS , Kibler WB , eds. Tennis Medicine A Complete Guide to Evaluation, Treatment, and Rehabilitation During Competitive Match-Play Tennis . Cham, Switzerland: Springer International Publishing AG

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Scott J. Montain, Samuel N. Cheuvront, and Henry C. Lukaski

Context:

Uncertainty exists regarding the effect of sustained sweating on sweat mineral-element composition.

Purpose:

To determine the effect of multiple hours of exercise-heat stress on sweat mineral concentrations.

Methods:

Seven heat-acclimated subjects (6 males, 1 female) completed 5 × 60 min of treadmill exercise (1.56 m/s, 2% grade) with 20 min rest between exercise periods in 2 weather conditions (27 °C, 40% relative humidity, 1 m/s and 35 °C, 30%, 1 m/s). Sweat was collected from a sweat-collection pouch attached to the upper back during exercise bouts 1, 3, and 5. Mineral elements were determined by using inductively coupled plasma-emission spectrography.

Results:

At 27 °C, sweat sodium (863 [563] µg/mL; mean [SD]), potassium (222 [48] µg/mL), calcium (16 [7]) µg/mL), magnesium (1265 [566] ng/mL), and copper (80 [56] ng/mL) remained similar to baseline over 7 h of exercise-heat stress, whereas sweat zinc declined 42–45% after the initial hour of exercise-heat stress (Ex1 = 655 [362], Ex3 = 382 [168], Ex5 = 355 [288] µg/mL, P < 0.05). Similar outcomes were observed for sweat zinc at 35 °C when sweat rates were higher. Sweat rate had no effect on sweat trace-element composition.

Conclusions:

Sweat sodium, potassium, and calcium losses during multiple hours of sustained sweating can be predicted from initial sweat composition. Estimates of sweat zinc losses, however, will be overestimated if sweat zinc conservation is not accounted for in sweat zinc-loss estimates.

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Andres E. Carrillo, René J. L. Murphy, and Stephen S. Cheung

Purpose:

Prolonged physical exertion and environmental heat stress may elicit postexercise depression of immune cell function, increasing upper respiratory tract infection (URTI) susceptibility. We investigated the effects of acute and short-term vitamin C (VC) compared with placebo (PL) supplementation on URTI susceptibility, salivary immunoglobulin A (s-IgA), and cortisol responses in healthy individuals following prolonged exercise-heat stress.

Methods:

Twelve participants were randomized into the VC or PL group in a double-blind design. For 12 days, participants consumed 3 × 500 mg tablets of VC or PL per day, with testing completed at baseline, then following acute (1 d) and short-term (8 d) supplementation. Participants performed 120.1 ± 49.6 min of cycling at 54 ± 6% VO2max in a hot (34.8 ± 1.0°C and 13 ± 3% relative humidity) environment, with saliva samples collected at pre-, post-, and 72 h postexercise. Health logs specifying URTI symptoms were completed for 7 days postexercise.

Results:

A 2 × 3 × 3 mixed ANOVA with a post hoc Bonferroni correction factor revealed a significant linear trend in postexercise cortisol attenuation in the VC group, 21.7 ± 15.1 nmol/L (mean ± SD) at baseline, to 13.5 ± 10.0 at acute, to 7.6 ± 4.2 after short term (P = .032). No differences were detected in ratio of s-IgA to protein or URTI symptoms between groups.

Conclusions:

These data suggest that vitamin C supplementation can decrease postexercise cortisol in individuals performing exercise similar to that of a half-marathon or marathon in hot conditions. However, no changes in s-IgA and URTI were evident, possibly due to previous moderate training and reduced physical and psychological stress compared with athletes participating in ultramarathons.

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Erica H. Gavel, Heather M. Logan-Sprenger, Joshua Good, Ira Jacobs, and Scott G. Thomas

(in percentage), and wind speed (in kilometers per hour) were measured with a heat stress tracker (Kestral 5400; Nielsen-Kellerman, Boothwyn, PA; accuracy, ±0.5°C, ±2% relative humidity [RH], wind speed ±3%). The participants provided their 24-hour food intake log and were asked to replicate it for