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Christopher Byrne and Jason K.W. Lee

proposition, as this would provide useful data on heat strain during training and competition, heat acclimatization status, and the effectiveness of interventions aimed at mitigating heat strain. A potential candidate is the physiological strain index (PSI) introduced by Moran et al 2 in 1998 as a novel and

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Margaret C. Morrissey, Michael R. Szymanski, Andrew J. Grundstein, and Douglas J. Casa

condition. Many EHS-prevention strategies have been adopted to enhance exercise heat tolerance, but not necessarily to decrease the incidence of EHS ( Alhadad, Tan, & Lee, 2019 ). Some examples of common strategies to enhance exercise heat tolerance include heat acclimatization (HA), hydration, work

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Scott J. Montain, Ronald J. Maughan, and Michael N. Sawka

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Douglas J. Casa, Yuri Hosokawa, Luke N. Belval, William M. Adams, and Rebecca L. Stearns

Exertional heat stroke (EHS) is among the leading causes of sudden death during sport and physical activity. However, previous research has shown that EHS is 100% survivable when rapidly recognized and appropriate treatment is provided. Establishing policies to address issues related to the prevention and treatment of EHS, including heat acclimatization, environment-based activity modification, body temperature assessment using rectal thermometry, and immediate, onsite treatment using cold-water immersion attenuates the risk of EHS mortality and morbidity. This article provides an overview of the current evidence regarding EHS prevention and management. The transfer of scientific knowledge to clinical practice has shown great success for saving EHS patients. Further efforts are needed to implement evidence-based policies to not only mitigate EHS fatality but also to reduce the overall incidence of EHS.

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Bent R. Rønnestad, Joar Hansen, Thomas C. Bonne, and Carsten Lundby

present case report does not provide any insights into potential mechanisms explaining the observed increase in Hb mass . Nonetheless, the increase in Hb mass has previously been linked to the more rapid increase in plasma volume known to occur with heat acclimatization and training. 3 Specifically it

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Amelia J. Carr, Philo U. Saunders, Laura A. Garvican-Lewis, and Brent S. Vallance

performance. 2 Prior to competing in hot environments, athletes’ preparation strategies may include, depending on their competition schedule and available facilities, heat acclimatization (living and training in a natural similar environment to the competition) 8 or acclimation (repeated heat exposures

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Sebastien Racinais, Martin Buchheit, Johann Bilsborough, Pitre C. Bourdon, Justin Cordy, and Aaron J. Coutts

Purpose:

To examine the physiological and performance responses to a heat-acclimatization camp in highly trained professional team-sport athletes.

Methods:

Eighteen male Australian Rules Football players trained for 2 wk in hot ambient conditions (31–33°C, humidity 34–50%). Players performed a laboratory-based heat-response test (24-min walk + 24 min seated; 44°C), a YoYo Intermittent Recovery Level 2 Test (YoYoIR2; indoor, temperate environment, 23°C) and standardized training drills (STD; outdoor, hot environment, 32°C) at the beginning and end of the camp.

Results:

The heat-response test showed partial heat acclimatization (eg, a decrease in skin temperature, heart rate, and sweat sodium concentration, P < .05). In addition, plasma volume (PV, CO rebreathing, +2.68 [0.83; 4.53] mL/kg) and distance covered during both the YoYoIR2 (+311 [260; 361] m) and the STD (+45.6 [13.9; 77.4] m) increased postcamp (P < .01). None of the performance changes showed clear correlations with PV changes (r < .24), but the improvements in running STD distance in hot environment were correlated with changes in hematocrit during the heat-response test (r = –.52, 90%CI [–.77; –.12]). There was no clear correlation between the performance improvements in temperate and hot ambient conditions (r < .26).

Conclusion:

Running performance in both hot and temperate environments was improved after a football training camp in hot ambient conditions that stimulated heat acclimatization. However, physiological and performance responses were highly individual, and the absence of correlations between physical-performance improvements in hot and temperate environments suggests that their physiological basis might differ.

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Cyril Schmit, Rob Duffield, Christophe Hausswirth, Aaron J. Coutts, and Yann Le Meur

Purpose:

To describe the effect of the initial perceptual experience from heat familiarization on the pacing profile during a freepaced endurance time trial (TT) compared with temperate conditions.

Methods:

Two groups of well-trained triathletes performed two 20-km TTs in either hot (35°C and 50% relative humidity [RH], n = 12) or temperate (21°C and 50% RH, n = 22) conditions, after standardization of training for each group before both trials. To ensure no physiological acclimation differences between conditions, the TTs for both groups were separated by 11 ± 4 d.

Results:

Performance improvement in the heat (11 ± 24 W) from the 1st to 2nd trial appeared comparable to that in temperate conditions (8 ± 14 W, P = .67). However, the specific alteration in pacing profile in the heat was markedly different than temperate conditions, with a change from “positive” to an “even” pacing strategy.

Conclusions:

Altered perceptions of heat during heat familiarization, rather than physiological acclimatization per se, may mediate initial changes in pacing and TT performance in the heat. These results highlight the need for athletes without time for sufficient heat acclimatization to familiarize themselves with hot conditions to reduce the uncertainty from behavior-based outcomes that may impede performance.

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.nata.org/career-education/education/online-ceu-opportunities/professional-development-center . Heat Illness and Heat Acclimatization Resources Help your athletes beat the heat as fall sports ramp up. NATA offers many resources related to heat illness and heat acclimatization. You can find all those resources and more at www.nata.org/practice-patient-care/health-issues . Apply for State

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Matt Brearley, Ian Norton, David Kingsbury, and Simon Maas

Introduction:

Anecdotal reports suggest that elite road motorcyclists suffer from high core body temperatures and physiological and perceptual strain when competing in hot conditions.

Methods:

Four male non-heat-acclimatized elite motorcyclists (3 Superbike, 1 Supersport) had their gastrointestinal temperature, heart rate, and respiratory rate measured and recorded throughout practice, qualifying, and race sessions of an Australian Superbike and Supersport Championship round contested in tropical conditions. Physiological strain was calculated during the sessions, and fluid-balance measures were taken during practice and qualifying. Rider thermal sensation was assessed immediately postsession.

Results:

Mean ambient temperature and relative humidity were 29.5–30.2°C and 64.5–68.7%, respectively, across the sessions. Gastrointestinal temperature rose from 37.6°C to 37.7°C presession at a median rate of 0.035°C, 0.037°C ,and 0.067°C/min during practice, qualifying, and race sessions to reach medians of 38.9°C, 38.8°C, and 39.1°C postsession, respectively. The peak postsession gastrointestinal temperature was 39.8°C. Median heart rates were ~164, 160, and 177 beats/min during the respective practice, qualifying, and race sessions, contributing to median physiological strain of 5.5, 5.6, and 6.2 across the sessions. Sweat rates were 1.01 and 0.90 L/h during practice and qualifying sessions, while rider thermal sensation was very hot after each session.

Conclusions:

This investigation confirms that elite road motorcyclists endure moderate to high physiological strain during practice, qualifying, and race sessions, exhibiting more-rapid rates of body-heat storage, higher core body temperatures, and higher physiological and perceptual strain than their stock-car-racing counterparts when competing in tropical conditions.