Yuri Hosokawa

The Timing of Exertional Heat Stroke Survival Starts prior to Collapse.

Adams et al. (1) reported that secondary school football coaches lacked a fundamental understanding of the causes and symptoms of exertional heat stroke (EHS). This lack of understanding was supported by the coaches’ inability to identify prevention strategies to minimize the risk of EHS and the symptoms they would look for in an athlete suspected of having EHS (1). This evidence helps support reasons for strong educational programs for on-site personnel and for employing athletic trainers (AT) at secondary schools to oversee the health and safety of the student athletes competing in school athletics programs.

Tarp-Assisted Cooling as a Method of Whole-Body Cooling in Hyperthermic Individuals

Study objective: We investigated the efficacy of tarp‐assisted cooling as a body cooling modality. Methods: Participants exercised on a motorized treadmill in hot conditions (ambient temperature 39.5°C [103.1°F], SD 3.1°C [5.58°F]; relative humidity 38.1% [SD 6.7%]) until they reached exercise‐induced hyperthermia. After exercise, participants were cooled with either partial immersion using a tarp‐assisted cooling method (water temperature 9.20°C [48.56°F], SD 2.81°C [5.06°F]) or passive cooling in a climatic chamber. Results: There were no differences in exercise duration (mean difference=0.10 minutes; 95% CI –5.98 to 6.17 minutes or end exercise rectal temperature (mean difference=0.10°C [0.18°F]; 95% CI –0.05°C to 0.25°C [–0.09°F to 0.45°F] between tarp‐assisted cooling (48.47 minutes [SD 8.27 minutes]; rectal temperature 39.73°C [103.51°F], SD 0.27°C [0.49°F]) and passive cooling (48.37 minutes [SD 7.10 minutes]; 39.63°C [103.33°F], SD 0.40°C [0.72°F]). Cooling time to rectal temperature 38.25°C (100.85°F) was significantly faster in tarp‐assisted cooling (10.30 minutes [SD 1.33 minutes]) than passive cooling (42.78 [SD 5.87 minutes]). Cooling rates for tarp‐assisted cooling and passive cooling were 0.17°C/min (0.31°F/min), SD 0.07°C/min (0.13°F/min) and 0.04°C/min (0.07°F/min), SD 0.01°C/min (0.02°F/min), respectively (mean difference=0.13°C [0.23°F]; 95% CI 0.09°C to 0.17°C [0.16°F to 0.31°F]. No sex differences were observed in tarp‐assisted cooling rates (men 0.17°C/min [0.31°F/min], SD 0.07°C/min [0.13°F/min]; women 0.16°C/min [0.29°F/min], SD 0.07°C/min [0.13°F/min]; mean difference=0.02°C/min [0.04°F/min]; 95% CI –0.06°C/min to 0.10°C/min [–0.11°F/min to 0.18°F/min]). Women (0.04°C/min [0.07°F/min], SD 0.01°C/min [0.02°F/min]) had greater cooling rates than men (0.03°C/min [0.05°F/min], SD 0.01°C/min [0.02°F/min]) in passive cooling, with negligible clinical effect (mean difference=0.01°C/min [0.02°F/min]; 95% CI 0.001°C/min to 0.024°C/min [0.002°F/min to 0.04°F/min]). Body mass was moderately negatively correlated with the cooling rate in passive cooling (r=–0.580) but not in tarp‐assisted cooling (r=–0.206). Conclusion: In the absence of a stationary cooling method such as cold‐water immersion, tarp‐assisted cooling can serve as an alternative, field‐expedient method to provide on‐site cooling with a satisfactory cooling rate.

Comparison of Gastrointestinal and Rectal Temperatures During Recovery After a Warm-Weather Road Race

CONTEXT It has been well established that gastrointestinal temperature (TGI) tracks closely with rectal temperature (TREC) during exercise. However, the field use of TGI pills is still being examined, and little is known about how measurements obtained using these devices compare during recovery after exercise in warm weather. OBJECTIVE To compare TGI and TREC in runners who completed an 11.3-km warm-weather road race and determine if runners with higher TGI and TREC present with greater passive cooling rates during recovery. DESIGN Cross-sectional study. SETTING Field. PATIENTS OR OTHER PARTICIPANTS Thirty recreationally active runners (15 men, 15 women; age = 39 ± 11 years, weight = 68.3 ± 11.7 kg, body fat = 19.2% ± 5.0%). MAIN OUTCOME MEASURE(S) The TGI and TREC were obtained immediately after the race and during a 20-minute passive rest at the 2014 Falmouth Road Race (heat index = 26.2°C ± 0.9°C). Temperatures were taken every 2 minutes during passive rest. The main dependent variables were mean bias and limits of agreement for TGI and TREC, using Bland-Altman analysis, and the 20-minute passive cooling rates for TGI and TREC. RESULTS No differences were evident between TGI and TREC throughout passive rest (P = .542). The passive cooling rates for TGI and TREC were 0.046 ± 0.031°C·min(-1) and 0.060 ± 0.036°C·min(-1), respectively. Runners with higher TGI and TREC at the start of cooling had higher cooling rates (R = 0.682, P < .001 and R = 0.54, P = .001, respectively). The mean bias of TGI during the 20-minute passive rest was -0.06°C ± 0.56°C with 95% limits of agreement of ±1.09°C. CONCLUSIONS After participants completed a warm-weather road race, TGI provided a valid measure of body temperature compared with the criterion measure of TREC. Therefore, TGI may be a viable option for monitoring postexercise-induced hyperthermia, if the pill is administered prophylactically.

Body-Cooling Paradigm in Sport: Maximizing Safety and Performance During Competition.

CONTEXT Although body cooling has both performance and safety benefits, knowledge on optimizing cooling during specific sport competition is limited. OBJECTIVES To identify when, during sport competition, it is optimal for body cooling and to identify optimal body-cooling modalities to enhance safety and maximize sport performance. EVIDENCE ACQUISITION A comprehensive literature search was conducted to identify articles with specific context regarding body cooling, sport performance, and cooling modalities used during sport competition. A search of scientific peer-reviewed literature examining the effects of body cooling on exercise performance was done to examine the influence of body cooling on exercise performance. Subsequently, a literature search was done to identify effective cooling modalities that have been shown to improve exercise performance. EVIDENCE SYNTHESIS The cooling modalities that are most effective in cooling the body during sport competition depend on the sport, timing of cooling, and feasibility based on the constraints of the sports rules and regulations. Factoring in the length of breaks (halftime substitutions, etc), the equipment worn during competition, and the cooling modalities that offer the greatest potential to cool must be considered in each individual sport. CONCLUSIONS Scientific evidence supports using body cooling as a method of improving performance during sport competition. Developing a strategy to use cooling modalities that are scientifically evidence-based to improve performance while maximizing athletes safety warrants further investigation.

Consensus Statement- Prehospital Care of Exertional Heat Stroke

Abstract Exertional heat stroke (EHS) is one of the most common causes of sudden death in athletes. It also represents a unique medical challenge to the prehospital healthcare provider due to the time sensitive nature of treatment. In cases of EHS, when cooling is delayed, there is a significant increase in organ damage, morbidity, and mortality after 30 minutes, faster than the average EMS transport and ED evaluation window. The purpose of this document is to present a paradigm for prehospital healthcare systems to minimize the risk of morbidity and mortality for EHS patients. With proper planning, EHS can be managed successfully by the prehospital healthcare provider.

Drugs and Supplements

The use of performance enhancing drugs and supplements in sport and physical activity has been around for decades; however, the impact of these drugs and supplements on performance in the heat has been garnering new attention. Although there are some drugs and supplements that can enhance performance in the heat, there are also many that may hinder performance, even potentially increasing the risk of serious illness or death in select circumstances. This chapter will describe and discuss specific drugs and supplements and their effects on performance and safety in the heat.

Extreme Heat Considerations in International Football Venues: The Utility of Climatologic Data in Decision Making

CONTEXT: Exposure to severe heat can have detrimental effects on athletic performance and increase the risk of exertional heat injuries. Therefore, proactive assessment of the environmental characteristics of international football match venues becomes critical in ensuring the safety and optimal performance of the athletes. OBJECTIVE: To propose the use of climatologic data (modeled wet-bulb globe temperature [WBGT]) in making athletic-event management decisions for the 2020 Summer Olympic Games and the 2022 Fédération Internationale de Football Association World Cup. DESIGN: Descriptive study. SETTING: Hourly meteorologic input data for a WBGT model were obtained from the second Modern-Era Retrospective Analysis for Research and Applications for Japan (Yokohama and Saitama) and Qatar (Doha and Al-Daayen). MAIN OUTCOME MEASURE(S):  The pattern of hourly WBGT and percentage of hours between 30°C and 32°C and exceeding 32°C WBGT during the expected competition periods for the 2020 Summer Olympic Games in Japan and the scheduled (November, December) and traditional (June, July) periods of the World Cup games in Qatar. RESULTS: The WBGT during the 2020 Olympic football tournament in Japan may exceed 30°C in 40% to 50% of the late mornings and early afternoons. The shift in tournament timing for the 2022 Fédération Internationale de Football Association World Cup in Qatar from the summer to late fall will reduce the exposure to ≥30°C WBGT to null. CONCLUSIONS: Directors of mass sporting events should consider using climatologic data in their organizational decision making to assess the potential heat illness risk and to implement risk-mitigation plans.

Fatal Exertional Heat Stroke and American Football Players: The Need for Regional Heat-Safety Guidelines

CONTEXT   Weather-based activity modification in athletics is an important way to minimize heat illnesses. However, many commonly used heat-safety guidelines include a uniform set of heat-stress thresholds that do not account for geographic differences in acclimatization. OBJECTIVE   To determine if heat-related fatalities among American football players occurred on days with unusually stressful weather conditions based on the local climate and to assess the need for regional heat-safety guidelines. DESIGN   Cross-sectional study. SETTING   Data from incidents of fatal exertional heat stroke (EHS) in American football players were obtained from the National Center for Catastrophic Sport Injury Research and the Korey Stringer Institute. PATIENTS OR OTHER PARTICIPANTS   Sixty-one American football players at all levels of competition with fatal EHSs from 1980 to 2014. MAIN OUTCOME MEASURE(S)   We used the wet bulb globe temperature (WBGT) and a z-score WBGT standardized to local climate conditions from 1991 to 2010 to assess the absolute and relative magnitudes of heat stress, respectively. RESULTS   We observed a poleward decrease in exposure WBGTs during fatal EHSs. In milder climates, 80% of cases occurred at above-average WBGTs, and 50% occurred at WBGTs greater than 1 standard deviation from the long-term mean; however, in hotter climates, half of the cases occurred at near average or below average WBGTs. CONCLUSIONS   The combination of lower exposure WBGTs and frequent extreme climatic values in milder climates during fatal EHSs indicates the need for regional activity-modification guidelines with lower, climatically appropriate weather-based thresholds. Established activity-modification guidelines, such as those from the American College of Sports Medicine, work well in the hotter climates, such as the southern United States, where hot and humid weather conditions are common.

Environmental Conditions and Seasonal Variables in American Youth Football Leagues

Our study describes youth football (YFB) environmental conditions and the associated heat index (HI) risk category. An observational research design was utilized. Independent variables included month, time, event, and geographic location. Main outcome variables were frequency of events, average HI, and corresponding risk categorization. The HI was recorded with the day and time for each YFB event across 2 YFB seasons. Nearly half (49.8%) of events were in a high HI risk category and 20.0% should have been cancelled. The hottest HI values were recorded in July and August (83.2 ± 9.4°F to 87.2 ± 10.9°F; 24.0% of YFB events). The 7 to 10 am time frame was cooler (67.7 ± 14.5°F; 6.3% of YFB events) than other time frames (P < .001). Hotter HI values were recorded in practices versus games (75.9 ± 14.1°F vs 70.6 ± 14.6°F; t = −6.426, P < .001). Starting the YFB season in September and holding weekend events in the early morning hours can decrease exposure to environmental heat stress.

Environmental Condition and Monitoring

The ambient environment (i.e., weather conditions) can significantly impact one’s ability to thermoregulate, particularly when exercising in environmentally stressful conditions where an imbalance between metabolic heat production and heat dissipation from the body is not adequately regulated. Empirical, direct, and rational heat indices have been developed by scientists to gauge the degree of heat strain one may experience in a range of thermal conditions. These measures are applied in athletic, military, and occupational settings to provide guidance on physical activity and/or clothing modifications that mitigate the risk of experiencing exertional heat illness. This chapter will provide an overview of common heat indices in physical activity settings and highlight the benefits and drawbacks of each index in practical applications. Lastly, the chapter will provide a case example from the Georgia High School Association in developing a set of weather-based activity modification guidelines based on an empirical study of football players’ heat injuries.