Susan W. Yeargin

National Athletic Trainers' Association Position Statement: Exertional Heat Illnesses.

OBJECTIVE To present best-practice recommendations for the prevention, recognition, and treatment of exertional heat illnesses (EHIs) and to describe the relevant physiology of thermoregulation. BACKGROUND Certified athletic trainers recognize and treat athletes with EHIs, often in high-risk environments. Although the proper recognition and successful treatment strategies are well documented, EHIs continue to plague athletes, and exertional heat stroke remains one of the leading causes of sudden death during sport. The recommendations presented in this document provide athletic trainers and allied health providers with an integrated scientific and clinically applicable approach to the prevention, recognition, treatment of, and return-to-activity guidelines for EHIs. These recommendations are given so that proper recognition and treatment can be accomplished in order to maximize the safety and performance of athletes. RECOMMENDATIONS Athletic trainers and other allied health care professionals should use these recommendations to establish onsite emergency action plans for their venues and athletes. The primary goal of athlete safety is addressed through the appropriate prevention strategies, proper recognition tactics, and effective treatment plans for EHIs. Athletic trainers and other allied health care professionals must be properly educated and prepared to respond in an expedient manner to alleviate symptoms and minimize the morbidity and mortality associated with these illnesses.

Cold water immersion: the gold standard for exertional heatstroke treatment.

The key to maximize the chances of surviving exertional heatstroke is rapidly decreasing the elevated core body temperature. Many methods exist to cool the body, but current evidence strongly supports the use of cold water. Preferably, the athlete should be immersed in cold water. If lack of equipment or staff prevents immersion, a continual dousing with cold water provides an effective cooling modality. We refute the many criticisms of this treatment and provide scientific evidence supporting cold water immersion for exertional heatstroke.

Influence of Hydration on Physiological Function and Performance During Trail Running in the Heat

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 degrees 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 degrees 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.

Acute Whole-Body Cooling for Exercise-Induced Hyperthermia: A Systematic Review

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.

Validity and Reliability of Devices That Assess Body Temperature During Indoor Exercise in the Heat

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 degrees C [97.5 +/- 2.16 degrees F], relative humidity = 52%) and cool laboratory (temperature = approximately 23.3 degrees C [74.0 degrees 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 degrees C (+/-0.50 degrees 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 degrees C [0.52 degrees F]), oral temperature using an inexpensive device (-1.13 degrees C [-2.03 degrees F]), temporal temperature measured according to the instruction manual (-0.87 degrees C [-1.56 degrees F]), temporal temperature using a modified technique (-0.63 degrees C [-1.13 degrees F]), oral temperature using an expensive device (-0.86 degrees C, [-1.55 degrees F]), aural temperature (-0.67 degrees C, [-1.20 degrees F]), axillary temperature using an inexpensive device (-1.25 degrees C, [-2.24 degrees F]), and axillary temperature using an expensive device (-0.94 degrees F [-1.70 degrees F]). Measurement of intestinal temperature (mean bias of -0.02 degrees C [-0.03 degrees 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 degrees C [0.16 degrees F] and r >or= 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.

Exertional heat stroke in competitive athletes

Exertional heat stroke (EHS) is a serious medical condition that can have a tragic outcome if proper assessment and treatment are not initiated rapidly. This article focuses on critical misconceptions that pertain to the prevention, recognition, and treatment of EHS, including 1) the randomness of EHS cases, 2) the role of nutritional supplements in EHS, 3) temperature assessment, 4) onset of EHS and the possible lucid interval, 5) rapid cooling, and 6) return to play. Exploration of these topics will enhance the medical care regarding EHS.

Body Cooling Between Two Bouts of Exercise in the Heat Enhances Subsequent Performance

The purpose was to assess whether body cooling between 2 bouts of exercise in the heat enhances performance during the second exercise session. Using a random, crossover design, 15 subjects (3 women, 12 men; 28 ± 2 years, 180 ± 2 cm, 69 ± 2.3 kg) participated in all 3 trials. Subjects ran 90 minutes on hilly trails in a hot environment (approximately 278C) before 12 minutes of either cold water immersion (CWI; 13.98° C), ice water immersion (IWI; 5.23° C), or a mock treatment (MT) of sitting in a tub with no water (29.50° C). After immersion, subjects ran a 2-mile race. CWI had faster (p < 0.05) performance time (725 seconds) than MT (769 seconds). CWI and IWI had significantly (p < 0.05) lower rectal temperatures postimmersion than MT as well as postrace (p < 0.05). Heart rate also remained significantly lower (p < 0.05) during the CWI and IWI trials for the first half of the race. In conclusion, CWI enhances performance (6% improvement in race time) in the second bout of exercise, supporting its potential role as an ergogenic aid in athletic performance.

Heat Acclimatization and Hydration Status of American Football Players During Initial Summer Workouts

This investigation evaluated the new National Collegiate Athletic Association model of heat acclimatization for football players using physiological, psychological, fluid balance, anthropometric, and nutritional variables. Eleven football players (20 ± 1 year, 1.88 ± 0.05 m, and 115.36 ± 18.85 kg) from a Division I football team were observed for the first 8 days of preseason practices. Measurements such as heart rate and gastrointestinal temperature (TGI) via telemetric sensor were taken before, 3 times during, and after practice daily. An average 1.39-kg (1.2%) decrease of body mass occurred from prepractice to postpractice (p ≤ 0.01). Consistent with mild body mass losses, urinary indices of hydration status (i.e., color, specific gravity, and osmolality) indicated mild fluid deficits. A significant increase (p ≤ 0.05) from pre-to postpractice was observed in urine color and urine specific gravity, but chronic hypohydration over the 8 days was not noted. The Environmental Symptoms Questionnaire (ESQ) postpractice score was significantly higher (p ≤ 0.05) than the prepractice score was, but averages did not differ across practice days. There was no difference in postpractice TGI measurements across days (p ≤ 0.05). Heart rate, TGI, and ESQ measurements indicated that football players experienced gradual heat acclimatization and enhanced heat tolerance, despite progressive increases of exercise variables, clothing, and environmental stressors.

Comprehensive Coach Education and Practice Contact Restriction Guidelines Result in Lower Injury Rates in Youth American Football

Background: Research evaluating the effect of comprehensive coach education and practice contact restriction in youth football injury rates is sparse. In 2012, USA Football released their Heads Up Football coaching education program (HUF), and Pop Warner Football (PW) instituted guidelines to restrict contact during practice. Purpose: To compare injury rates among youth football players aged 5 to 15 years by whether their leagues implemented HUF and/or were PW-affiliated. Study Design: Cohort study; Level of evidence, 2. Methods: Athletic trainers (ATs) evaluated and tracked injuries at each practice and game during the 2014 youth football season. Players were drawn from 10 leagues across 4 states. The non–Heads Up Football (NHUF) group consisted of 704 players (none of whom were PW-affiliated) from 29 teams within 4 leagues. The HUF+PW group consisted of 741 players from 27 teams within 2 leagues. The HUF-only group consisted of 663 players from 44 teams within 4 leagues. Injury rates and injury rate ratios (IRRs) were reported with 95% CIs. Results: A total of 370 injuries were reported during 71,262 athlete-exposures (AEs) (rate, 5.19/1000 AEs). Compared with the NHUF group (7.32/1000 AEs), the practice injury rates were lower for the HUF+PW group (0.97/1000 AEs; IRR, 0.13; 95% CI, 0.08-0.21) and the HUF-only group (2.73/1000 AEs; IRR, 0.37; 95% CI, 0.26-0.53). Compared with the NHUF group (13.42/1000 AEs), the game injury rate was lower for the HUF+PW group (3.42/1000 AEs; IRR, 0.25; 95% CI, 0.15-0.44) but not for the HUF-only group (13.76/1000 AEs; IRR, 1.02; 95% CI, 0.73-1.43). Also, the HUF+PW game injury rate was lower than that of HUF-only (IRR, 0.20; 95% CI, 0.12-0.36). Higher injury rates were typically found in those aged 11 to 15 years compared with those aged 5 to 10 years. However, stronger effects related to HUF implementation and PW affiliation were seen among 11- to 15-year-olds. When restricted to concussions only, the sole difference was found between the practice concussion rates among 11- to 15-year-olds in the HUF+PW (0.14/1000 AEs) and NHUF groups (0.79/1000 AEs) (IRR, 0.18; 95% CI, 0.04-0.85). Conclusion: These findings support comprehensive coach education and practice contact restrictions as effective methods of injury mitigation. Future research should continue evaluating similar programming within other levels of competition and sports.

Cold-water dousing with ice massage to treat exertional heat stroke: a case series.

INTRODUCTION We sought to determine the rate of cooling via a novel water ice therapy (WIT) as an alternative to cold-water immersion for the acute treatment of exertional heat stroke (EHS). METHODS Observations were made at the 2004-2008 Marine Corps Marathons (mean +/- SD: 16.3 +/- 4.9 degrees C dry bulb, 32 +/- 6% RH). Nine (seven men, two women) EHS patients (33 +/- 6 yr of age; 268 +/- 54 min average race time for six who finished) were observed during on-site treatment. Patients were treated while lying supine on a porous stretcher resting on a tub filled with cold water (approximately 10-12 degrees C). Medical personnel monitored T(re), doused the patient with water and massaged major muscle groups with ice bags until T(re) decreased to 38.9 degrees C. Patients were not immersed in water. Serial T(re) and time were used to calculate cooling rates. RESULTS Final T(re) (39.12 +/- 0.63 degrees C) was significantly lower than initial T(re) (41.43 +/- 0.71 degrees C, P < 0.05). Cooling rates were 0.13 +/- 0.04 degrees C min(-1). The decrease in T(re) for the initial 6 min of WIT (0.38 +/- 0.13 degrees C) was significantly less than for the subsequent 6-min time period (1.31 +/- 0.34 degrees C, P < 0.001). Cooling rates for these time periods were significantly different (0.06 +/- 0.02 degrees C x min(-1) and 0.22 +/- 0.06 degrees C x min(-1), respectively, P < 0.05). Initial T(re) was not correlated with overall cooling rate (r = 0.434, P = 0.244), or total cooling time required (17 +/- 4 min; r = 0.207, P = 0.593). Survival rate was 100%. CONCLUSION WIT provided cooling rates that were 70% as effective as those published for cold-water immersion with 8 degrees C water (0.19 degrees C x min(-1)) and resulted in 100% patient survival.