Objective: To present evidence-based recommendations that promote optimized fluid-maintenance practices for physically active individuals. Background: Both a lack of adequate fluid replacement (hypohydration) and excessive intake (hyperhydration) can compromise athletic performance and increase health risks. Athletes need access to water to prevent hypohydration during physical activity but must be aware of the risks of overdrinking and hyponatremia. Drinking behavior can be modified by education, accessibility, experience, and palatability. This statement updates practical recommendations regarding fluid-replacement strategies for physically active individuals. Recommendations: Educate physically active people regarding the benefits of fluid replacement to promote performance and safety and the potential risks of both hypohydration and hyperhydration on health and physical performance. Quantify sweat rates for physically active individuals during exercise in various environments. Work with individuals to develop fluid-replacement practices that promote sufficient but not excessive hydration before, during, and after physical activity.

Context Clinicians and athletes can benefit from field-expedient measurement tools, such as urine color, to assess hydration state; however, the diagnostic efficacy of this tool has not been established. Objective To determine the diagnostic accuracy of urine color assessment to distinguish a hypohydrated state (≥2% body mass loss [BML]) from a euhydrated state (<2% BML) after exercise in a hot environment. Design Controlled laboratory study. Setting Environmental chamber in a laboratory. Patients or Other Participants Twenty-two healthy men (age = 22 ± 3 years, height = 180.4 ± 8.7 cm, mass = 77.9 ± 12.8 kg, body fat = 10.6% ± 4.6%). Intervention(s) Participants cycled at 68% ± 6% of their maximal heart rates in a hot environment (36°C ± 1°C) for 5 hours or until 5% BML was achieved. At the point of each 1% BML, we assessed urine color. Main Outcome Measure(s) Diagnostic efficacy of urine color was assessed using receiver operating characteristic curve analysis, sensitivity, specificity, and likelihood ratios. Results Urine color was useful as a diagnostic tool to identify hypohydration after exercise in the heat (area under the curve = 0.951, standard error = 0.022; P < .001). A urine color of 5 or greater identified BML ≥2% with 88.9% sensitivity and 84.8% specificity (positive likelihood ratio = 5.87, negative likelihood ratio = 0.13). Conclusions Under the conditions of acute dehydration due to exercise in a hot environment, urine color assessment can be a valid, practical, inexpensive tool for assessing hydration status. Researchers should examine the utility of urine color to identify a hypohydrated state under different BML conditions.

Context: The sensation of thirst is different from the complex behavior of drinking ad libitum. Rehydration recommendations to athletes differ, depending on the source, yet no previous researchers have systematically compared drinking to thirst (D TT ) versus ad libitum drinking behavior (D AL ). Objective: To compare 2 groups of trained cyclists (D TT and D AL ) who had similar physical characteristics and training programs ( P > .05). The D TT group (n = 12, age = 47 ± 7 years) drank only when thirsty, whereas the D AL group (n = 12, age = 44 ± 7 years) consumed fluid ad libitum (ie, whenever and in whatever volume desired). Design: Cohort study. Setting: Road cycling (164 km) in the heat (36.1°C ± 6.5°C). Patients or Other Participants: Ultraendurance cyclists (4 women, 20 men). Intervention(s): We recorded measurements 1 day before the event, on event day before the start, at 3 roadside aid stations, at the finish line, and 1 day after the event. Main Outcome Measure(s): Body mass, urinary hydration indices, and food and fluids consumed. Results: No between-groups differences were seen on event day for total exercise time (D TT = 6.69 ± 0.89 hours, D AL = 6.66 ± 0.77 hours), urinary indices (specific gravity, color), body mass change (D TT = −2.22% ± 1.73%, D AL = −2.29% ± 1.62%), fluid intake (D TT = 5.63 ± 2.59 L/6.7 h, D AL = 6.04 ± 2.37 L/6.7 h), dietary energy intake, macronutrient intake, ratings of thirst (D TT start = 2 ± 1, D TT finish = 6 ± 1, D AL start = 2 ± 1, D AL finish = 6 ± 1), pain, perceived exertion, or thermal sensation. Total fluid intake on recovery day +1 was the primary significant difference (D AL = 5.13 ± 1.87 L/24 h, D TT = 3.13 ± 1.53 L/24 h, t 18 = 2.59, P = .02). Conclusions: Observations on event day indicated that drinking to thirst and drinking ad libitum resulted in similar physiologic and perceptual outcomes. This suggests that specific instructions to “drink to thirst” were unnecessary. Indeed, if athletes drink ad libitum, they can focus on training and competition rather than being distracted by ongoing evaluation of thirst sensations.

Context: Athletic trainers recommend and use a multitude of rehydration (REHY) methods with their patients. The REHY modality that most effectively facilitates recovery is unknown. Objective: To compare 5 common REHY methods for thermoregulatory and stress hormone recovery after exercise dehydration (EXDE) in trained participants. Design: Randomized, cross-over, controlled study. Patients or Other Participants: Twelve physically active, non–heat-acclimatized men (age = 23 ± 4 years, height = 180 ± 6 cm, mass = 81.3 ± 3.7 kg, V̇ o 2 max = 56.9 ± 4.4 mL·min −1 ·kg −1 , body fat = 7.9% ± 3%) participated. Intervention(s): Participants completed 20-hour fluid restriction and 2-hour EXDE; they then received no fluid (NF) or REHY (half-normal saline) via ad libitum (AL), oral (OR), intravenous (IV), or combination IV and OR (IV + OR) routes for 30 minutes; and then were observed for another 30 minutes. Main Outcome Measure(s): Body mass, rectal temperature, 4-site mean weighted skin temperature, plasma stress hormone concentrations, and environmental symptoms questionnaire (ESQ) score. Results: Participants were hypohydrated (body mass −4.23% ± 0.22%) post-EXDE. Rectal temperature for the NF group was significantly greater than for the IV group ( P = .023) at 30 minutes after beginning REHY (REHY30) and greater than OR, IV, and IV + OR ( P ≤ .009) but not AL ( P = .068) at REHY60. Mean weighted skin temperature during AL was less than during IV + OR at REHY5 ( P = .019). The AL participants demonstrated increased plasma cortisol concentrations compared with IV + OR, independent of time ( P = .015). No differences existed between catecholamine concentrations across treatments ( P > .05). The ESQ score was increased at REHY60 for NF, AL, OR, and IV ( P < .05) but not for IV + OR ( P = .217). The NF ESQ score was greater than that of IV + OR at REHY60 ( P = .012). Conclusions: Combination IV + OR REHY reduced body temperature to a greater degree than OR and AL REHY when compared with NF. Future studies addressing clinical implications are needed.

Context Cold-water immersion is the criterion standard for treatment of exertional heat illness. Cryotherapy and water immersion also have been explored as ergogenic or recovery aids. The kinetics of inflammatory markers, such as interleukin-6 (IL-6), during cold-water immersion have not been characterized. Objective To characterize serum IL-6 responses to water immersion at 2 temperatures and, therefore, to initiate further research into the multidimensional benefits of immersion and the evidence-based selection of specific, optimal immersion conditions by athletic trainers. Design Controlled laboratory study. Setting Human performance laboratory Patients or Other Participants Eight college-aged men (age = 22 ± 3 years, height = 1.76 ± 0.08 m, mass = 77.14 ± 9.77 kg, body fat = 10% ± 3%, and maximal oxygen consumption = 50.48 ± 4.75 mL·kg −1 ·min −1 ). Main Outcome Measures Participants were assigned randomly to receive either cold (11.70°C ± 2.02°C, n = 4) or warm (23.50°C ± 1.00°C, n = 4) water-bath conditions after exercise in the heat (temperature = 37°C, relative humidity = 52%) for 90 minutes or until volitional cessation. Results Whole-body cooling rates were greater in the cold water-bath condition for the first 6 minutes of water immersion, but during the 90-minute, postexercise recovery, participants in the warm and cold water-bath conditions experienced similar overall whole-body cooling. Heart rate responses were similar for both groups. Participants in the cold water-bath condition experienced an overall slight increase (30.54% ± 77.37%) in IL-6 concentration, and participants in the warm water-bath condition experienced an overall decrease (−69.76% ± 15.23%). Conclusions We have provided seed evidence that cold-water immersion is related to subtle IL-6 increases from postexercise values and that warmer water-bath temperatures might dampen this increase. Further research will elucidate any anti-inflammatory benefit associated with water-immersion treatment and possible multidimensional uses of cooling therapies.

Context: Exertional heat stroke (EHS) is one of the leading causes of death in athletes. Certified athletic trainers (ATs) demonstrate strong knowledge of recommended practices with EHS but are apprehensive in implementing 2 basic procedures: rectal temperature assessment and cold water immersion. This apprehension might lead to deaths from EHS that could have been prevented. Objective: To investigate why collegiate and high school ATs do not implement best practices for the recognition and treatment of EHS. Design: Qualitative study. Setting: In-person focus groups consisting of 3 to 6 collegiate or high school ATs. Patients or Other Participants: A total of 19 ATs (9 men, 10 women; age = 36 ± 10 years, length of certification = 12 ± 9 years) employed at either the collegiate (n = 10) or high school (n = 9) level participated in the study. Data Collection and Analysis: Interviews were transcribed verbatim, and data were analyzed using deductive data analysis. Peer review and multiple-analyst data triangulation were conducted to establish trustworthiness of the data. Results: Five emergent themes explained the lack of evidence-based practice (EBP) regarding recognition and treatment of EHS. Three themes (lack of knowledge, comfort level, lack of initiative) were common in both the collegiate and high school settings, and 2 separate themes (liability concerns, lack of resources) were present in the high school setting. Conclusions: Our findings are consistent with those in the literature on EBP and EHS. Regardless of clinical setting, ATs have basic information on recognition and treatment of EHS, but 5 themes act as barriers to implementing proper management in the clinical setting. Workshops or hands-on training sessions need to be made available to improve students' comfort levels so ATs will implement EBP into everyday settings.

Context: Athletic trainers (ATs) know to diagnose exertional heat stroke (EHS) via rectal thermometry (T re ) and to treat EHS via cold-water immersion (CWI) but do not implement these recommendations in clinical practice. Objective: To gain an understanding of educational techniques used to deliver content regarding EHS. Design: Qualitative study. Setting: In-person focus groups at the National Athletic Trainers' Association (NATA) Annual Meeting in June 2009 and 2 follow-up telephone interviews to confirm emergent themes. Patients or Other Participants: Thirteen AT educators (11 men, 2 women) from programs accredited by the Commission on Accreditation of Athletic Training Education, with an average of 22 ± 9 years of clinical experience and 16 ± 10 years of experience as educators. Five NATA districts were represented. Data Collection and Analysis: Data were analyzed using inductive content analysis. Peer review and data source triangulation also were conducted to establish trustworthiness. Results: Four themes emerged from the analysis: educational techniques, educational competencies, previous educational training, and privacy/public opinion. Educational techniques highlighted the lack of hands-on training for T re and CWI. Educational competencies referred to the omission of T re and CWI as psychomotor skills. Previous educational training addressed educators not having the skills or comfort with the skills necessary to properly educate students. Privacy/public opinion comprised external inputs from various groups (parents and coaches), legal considerations, and social bias. Conclusions: Educators supplied students with the appropriate didactic knowledge about EHS, but their lack of training and misgivings about T re prevented them from allowing students to gain competence with this skill. Until the NATA competencies state the need to teach T re and CWI and until educators are provided with their own learning opportunities, evidence-based practice regarding EHS will be lacking.

Context: Authors of most field studies have not observed decrements in physiologic function and performance with increases in dehydration, although authors of well-controlled laboratory studies have consistently reported this relationship. Investigators in these field studies did not control exercise intensity, a known modulator of body core temperature. Objective: To directly examine the effect of moderate water deficit on the physiologic responses to various exercise intensities in a warm outdoor setting. Design: Semirandomized, crossover design. Setting: Field setting. Patients or Other Participants: Seventeen distance runners (9 men, 8 women; age = 27 ± 7 years, height = 171 ± 9 cm, mass = 64.2 ± 9.0 kg, body fat = 14.6% ± 5.5%). Intervention(s): Participants completed four 12-km runs (consisting of three 4-km loops) in the heat (average wet bulb globe temperature = 26.5°C): (1) a hydrated, race trial (HYR), (2) a dehydrated, race trial (DYR), (3) a hydrated, submaximal trial (HYS), and (4) a dehydrated, submaximal trial (DYS). Main Outcome Measure(s): For DYR and DYS trials, dehydration was measured by body mass loss. In the submaximal trials, participants ran at a moderate pace that was matched by having them speed up or slow down based on pace feedback provided by researchers. Intestinal temperature was recorded using ingestible thermistors, and participants wore heart rate monitors to measure heart rate. Results: Body mass loss in relation to a 3-day baseline was greater for the DYR (−4.30% ± 1.25%) and DYS trials (−4.59% ± 1.32%) than for the HYR (−2.05% ± 1.09%) and HYS (−2.0% ± 1.24%) trials postrun ( P < .001). Participants ran faster for the HYR (53.15 ± 6.05 minutes) than for the DYR (55.7 ± 7.45 minutes; P < .01), but speed was similar for HYS (59.57 ± 5.31 minutes) and DYS (59.44 ± 5.44 minutes; P > .05). Intestinal temperature immediately postrun was greater for DYR than for HYR ( P < .05), the only significant difference. Intestinal temperature was greater for DYS than for HYS postloop 2, postrun, and at 10 and 20 minutes postrun (all: P < .001). Intestinal temperature and heart rate were 0.22°C and 6 beats/min higher, respectively, for every additional 1% body mass loss during the DYS trial compared with the HYS trial. Conclusions: A small decrement in hydration status impaired physiologic function and performance while trail running in the heat.

Context: Previous research has indicated that despite awareness of the current literature on the recommended prevention and care of exertional heat stroke (EHS), certified athletic trainers (ATs) acknowledge failure to follow those recommendations. Objective: To investigate the current knowledge, attitudes, and practices of ATs regarding the recognition and treatment of EHS. Design: Cross-sectional study. Setting: Online survey. Patients or Other Participants: We obtained a random sample of e-mail addresses for 1000 high school and collegiate ATs and contacted these individuals with invitations to participate. A total of 498 usable responses were received, for a 25% response rate. Main Outcome Measure(s): The survey instrument evaluated ATs' knowledge and actual practice regarding EHS and included 29 closed-ended Likert scale questions (1 = strongly disagree , 7 = strongly agree ), 2 closed-ended questions rated on a Likert scale (1 = lowest value , 9 = greatest value ), 8 open-ended questions, and 7 demographic questions. We focused on the open-ended and demographic questions. Results: Although most ATs (77.1%) have read the current National Athletic Trainers' Association position statement on heat illness, only 18.6% used rectal thermometers to assess core body temperature to recognize EHS, and 49.7% used cold-water immersion to treat EHS. Athletic trainers perceived rectal thermometers as the most valid temperature assessment device when compared with other assessment devices ( P ≤ .05), but they used oral thermometers as the primary assessment tool (49.1%). They identified cold-water immersion as the best cooling method ( P ≤ .05), even though they used other means to cool a majority of the time (50.3%). Conclusions: The ATs surveyed have sound knowledge of the correct means of EHS recognition and treatment. However, a significant portion of these ATs reported using temperature assessment devices that are invalid with athletes exercising in the heat. Furthermore, they reported using cooling treatment methods that have inferior cooling rates.

Context: Previous researchers have not investigated the thermoregulatory responses to multiple consecutive days of American football in adolescents. Objective: To examine the thermoregulatory and hydration responses of high school players during formal preseason football practices. Design: Observational study. Setting: Players practiced outdoors in late August once per day on days 1 through 5, twice per day on days 6 and 7, and once per day on days 8 through 10. Maximum wet bulb globe temperature averaged 23 ± 4°C. Patients or Other Participants: Twenty-five heat-acclimatized adolescent boys (age = 15 ± 1 years, height = 180 ± 8 cm, mass = 81.4 ± 15.8 kg, body fat = 12 ± 5%, Tanner stage = 4 ± 1). Main Outcome Measure(s): We observed participants within and across preseason practices of football. Measures included gastrointestinal temperature (T GI ), urine osmolality, sweat rate, forearm sweat composition, fluid consumption, testosterone to cortisol ratio, perceptual measures of thirst, perceptual measures of thermal sensation, a modified Environmental Symptoms Questionnaire, and knowledge questionnaires assessing the participants' understanding of heat illnesses and hydration. Results were analyzed for differences across time and were compared between younger (14–15 years, n = 13) and older (16–17 years, n = 12) participants. Results: Maximum daily T GI values remained less than 40°C and were correlated with maximum wet bulb globe temperature ( r = 0.59, P = .009). Average urine osmolality indicated that participants generally experienced minimal to moderate hypohydration before (881 ± 285 mOsmol/kg) and after (856 ± 259 mOsmol/kg) each practice as a result of replacing approximately two-thirds of their sweat losses during exercise but inadequately rehydrating between practices. Age did not affect most variables; however, sweat rate was lower in younger participants (0.6 ± 0.2 L/h) than in older participants (0.8 ± 0.1 L/h) ( F 1,18 = 8.774, P = .008). Conclusions: Previously heat-acclimatized adolescent boys (T GI < 40°C) can safely complete the initial days of preseason football practice in moderate environmental conditions using well-designed practice guidelines. Adolescent boys replaced most sweat lost during practice but remained mildly hypohydrated throughout data collection, indicating inadequate hydration habits when they were not at practice.

Context: The protective equipment worn during American football has been shown to increase thermal strain; however, the perception of this increased heat has not been examined. Objective: To evaluate perceptual responses of American football players while wearing different uniforms during exercise in the heat and to evaluate how these responses may be used to monitor athlete safety. Design: Randomized controlled trial. Setting: Human Performance Laboratory. Patients or Other Participants: Ten men with more than 3 years of competitive experience as football linemen (age = 23.8 ± 1.3 years, height = 183.9 ± 1.8 cm, mass = 117.4 ± 3.5 kg, body fat = 30.1% ± 1.7%) participated. Intervention(s): On 3 occasions in hot, humid (33°C, 48%–49% relative humidity) environmental conditions, participants completed 10 minutes of strenuous repetitive box lifting (RBL), 10 minutes of seated rest, and up to 60 minutes of treadmill walking. At each trial, they wore a different uniform condition: control (CON) clothing comprising shorts, socks, and sneakers; partial (PART) National Football League (NFL) uniform comprising the uniform without helmet or shoulder pads; or full (FULL) NFL uniform. Exercise, meals, and hydration status were controlled. Main Outcome Measure(s): Rectal temperature (T re ), skin temperature (T sk ), rating of perceived exertion (RPE), thermal perception (THM), perception of thirst (TST), and perception of muscle pain (MPN) were obtained for time points matched across trials. Results: Nineteen of the 30 trials ended before 60 minutes of treadmill walking as a result of participant exhaustion. Mean treadmill time was longer for the CON condition (51.7 ± 13.4 minutes) than for the PART (43.1 ± 15.6 minutes; t 9 = 3.092, P = .01) or the FULL (36.2 ± 13.2 minutes; t 9 = 4.393, P = .002) conditions. Neck and forearm T sk increased between the initial time point and the end of exercise in the PART (33.6 ± 0.9°C and 35.0 ± 0.6°C, respectively; F 2,18 = 9.034, P < .001) and the FULL (33.4 ± 0.9°C and 35.2 ± 0.6°C, respectively; F 2,18 = 21.011, P = .002) conditions. Rate of T re rise was greater in the FULL (0.042 ± 0.010°C/min) than in the PART (0.034 ± 0.006°C/min) condition ( F 2,27 = 10.69, P = .04). We found a relationship at the post-RBL and final time points between RPE and THM ( r = 0.75, P < .001 and r = 0.59, P < .001, respectively), RPE and TST ( r = 0.76, P < .001 and r = 0.61, P < .001, respectively), and RPE and MPN ( r = 0.63, P < .001 and r = 0.64, P < .001, respectively). The RPE was greater at the end of exercise in the PART (17 ± 2) and FULL (18 ± 1) conditions than in the CON (15 ± 3) condition ( F 2,18 = 7.403, P = .005). Conclusions: Although no differences in perceptual scales existed between the PART and FULL conditions, the T sk and rate of T re increase differed, indicating that football athletes find it difficult to perceptually rate exercise conditions as potentially dangerous hyperthermia develops. In addition, correlations between the perceptual scales further defined perceptual responses during exercise in the heat.

Context: In hot environments, the American football uniform predisposes athletes to exertional heat exhaustion or exercise-induced hyperthermia at the threshold for heat stroke (rectal temperature [T re ] > 39°C). Objective: To evaluate the differential effects of 2 American football uniform configurations on exercise, thermal, cardiovascular, hematologic, and perceptual responses in a hot, humid environment. Design: Randomized controlled trial. Setting: Human Performance Laboratory. Patients or Other Participants: Ten men with more than 3 years of competitive experience as football linemen (age = 23.8 ± 4.3 years, height = 183.9 ± 6.3 cm, mass = 117.41 ± 12.59 kg, body fat = 30.1% ± 5.5%). Intervention(s): Participants completed 3 controlled exercise protocols consisting of repetitive box lifting (lifting, carrying, and depositing a 20.4-kg box at a rate of 10 lifts per minute for 10 minutes), seated recovery (10 minutes), and up to 60 minutes of treadmill walking. They wore one of the following: a partial uniform (PART) that included the National Football League (NFL) uniform without a helmet and shoulder pads; a full uniform (FULL) that included the full NFL uniform; or control clothing (CON) that included socks, sneakers, and shorts. Exercise, meals, and hydration status were controlled. Main Outcome Measure(s): We assessed sweat rate, T re , heart rate, blood pressure, treadmill exercise time, perceptual measurements, plasma volume, plasma lactate, plasma glucose, plasma osmolality, body mass, and fat mass. Results: During 19 of 30 experiments, participants halted exercise as a result of volitional exhaustion. Mean sweat rate, T re , heart rate, and treadmill exercise time during the CON condition were different from those measures during the PART ( P range, .04–.001; d range, 0.42–0.92) and FULL ( P range, .04–.003; d range, 1.04–1.17) conditions; no differences were detected for perceptual measurements, plasma volume, plasma lactate, plasma glucose, or plasma osmolality. Exhaustion occurred during the FULL and PART conditions at the same T re (39.2°C). Systolic and diastolic blood pressures (n = 9) indicated that hypotension developed throughout exercise (all treatments). Compared with the PART condition, the FULL condition resulted in a faster rate of T re increase ( P < .001, d = 0.79), decreased treadmill exercise time ( P = .005, d = 0.48), and fewer completed exercise bouts. Interestingly, T re increase was correlated with lean body mass during the FULL condition ( R 2 = 0.71, P = .005), and treadmill exercise time was correlated with total fat mass during the CON ( R 2 = 0.90, P < .001) and PART ( R 2 = 0.69, P = .005) conditions. Conclusions: The FULL and PART conditions resulted in greater physiologic strain than the CON condition. These findings indicated that critical internal temperature and hypotension were concurrent with exhaustion during uncompensable (FULL) or nearly uncompensable (PART) heat stress and that anthropomorphic characteristics influenced heat storage and exercise time to exhaustion.

Context: When assessing exercise hyperthermia outdoors, the validity of certain commonly used body temperature measuring devices has been questioned. A controlled laboratory environment is generally less influenced by environmental factors (eg, ambient temperature, solar radiation, wind) than an outdoor setting. The validity of these temperature measuring devices in a controlled environment may be more acceptable. Objective: To assess the validity and reliability of commonly used temperature devices compared with rectal temperature in individuals exercising in a controlled, high environmental temperature indoor setting and then resting in a cool environment. Design: Time series study. Setting: Laboratory environmental chamber (temperature = 36.4 ± 1.2°C [97.5 ± 2.16°F], relative humidity = 52%) and cool laboratory (temperature = approximately 23.3°C [74.0°F], relative humidity = 40%). Patients or Other Participants: Fifteen males and 10 females. Intervention(s): Rectal, gastrointestinal, forehead, oral, aural, temporal, and axillary temperatures were measured with commonly used temperature devices. Temperature was measured before and 20 minutes after entering the environmental chamber, every 30 minutes during a 90-minute treadmill walk in the heat, and every 20 minutes during a 60-minute rest in mild conditions. Device validity and reliability were assessed with various statistical measures to compare the measurements using each device with rectal temperature. A device was considered invalid if the mean bias (average difference between rectal and device temperatures) was more than ±0.27°C (±0.50°F). Main Outcome Measure(s): Measured temperature from each device (mean and across time). Results: The following devices provided invalid estimates of rectal temperature: forehead sticker (0.29°C [0.52°F]), oral temperature using an inexpensive device (−1.13°C [−2.03°F]), temporal temperature measured according to the instruction manual (−0.87°C [−1.56°F]), temporal temperature using a modified technique (−0.63°C [−1.13°F]), oral temperature using an expensive device (−0.86°C, [−1.55°F]), aural temperature (−0.67°C, [−1.20°F]), axillary temperature using an inexpensive device (−1.25°C, [−2.24°F]), and axillary temperature using an expensive device (−0.94°F [−1.70°F]). Measurement of intestinal temperature (mean bias of −0.02°C [−0.03°F]) was the only device considered valid. Devices measured in succession (intestinal, forehead, temporal, and aural) showed acceptable reliability (all had a mean bias = 0.09°C [0.16°F] and r ≥ 0.94]). Conclusions: Even during laboratory exercise in a controlled environment, devices used to measure forehead, temporal, oral, aural, and axillary body sites did not provide valid estimates of rectal temperature. Only intestinal temperature measurement met the criterion. Therefore, we recommend that rectal or intestinal temperature be used to assess hyperthermia in individuals exercising indoors in the heat.

Objective: To critically assess original research addressing the effect of creatine supplementation on exercise heat tolerance and hydration status. Data Sources: We searched the electronic databases PubMed, Scopus, Web of Science, SPORTDiscus, and Rehabilitation & Physical Medicine, without date limitations, for the following key words: creatine , exercise , thermoregulation , dehydration , hyperthermia , heat tolerance, exertional heat illnesses , and renal function . Our goal was to identify randomized clinical trials investigating the effect of creatine supplementation on hydration status and thermoregulation. Citations from related articles also were identified and retrieved. Data Synthesis: Original research was reviewed using the Physiotherapy Evidence Database (PEDro) Scale. One author initially screened all articles. Fifteen of 95 articles examined the effects of creatine on thermoregulation or hydration status (or both). Two independent reviewers then reviewed these articles. Ten studies were selected on the basis of inclusion and exclusion criteria. The PEDro scores for the 10 studies ranged from 7 to 10 points (maximum possible score = 10 points). Conclusions: No evidence supports the concept that creatine supplementation either hinders the body's ability to dissipate heat or negatively affects the athlete's body fluid balance. Controlled experimental trials of athletes exercising in the heat resulted in no adverse effects from creatine supplementation at recommended dosages.

Objective: To assess existing original research addressing the efficiency of whole-body cooling modalities in the treatment of exertional hyperthermia. Data Sources: During April 2007, we searched MEDLINE, EMBASE, Scopus, SportDiscus, CINAHL, and Cochrane Reviews databases as well as ProQuest for theses and dissertations to identify research studies evaluating whole-body cooling treatments without limits. Key words were cooling , cryotherapy , water immersion , cold-water immersion , ice-water immersion , icing , fanning , bath , baths , cooling modality , heat illness , heat illnesses , exertional heatstroke , exertional heat stroke , heat exhaustion , hyperthermia , hyperthermic , hyperpyrexia , exercise , exertion , running , football , military , runners , marathoner , physical activity , marathoning , soccer , and tennis . Data Synthesis: Two independent reviewers graded each study on the Physiotherapy Evidence Database (PEDro) scale. Seven of 89 research articles met all inclusion criteria and a minimum score of 4 out of 10 on the PEDro scale. Conclusions: After an extensive and critical review of the available research on whole-body cooling for the treatment of exertional hyperthermia, we concluded that ice-water immersion provides the most efficient cooling. Further research comparing whole-body cooling modalities is needed to identify other acceptable means. When ice-water immersion is not possible, continual dousing with water combined with fanning the patient is an alternative method until more advanced cooling means can be used. Until future investigators identify other acceptable whole-body cooling modalities for exercise-induced hyperthermia, ice-water immersion and cold-water immersion are the methods proven to have the fastest cooling rates.