Youth football: heat stress and injury risk

Subjective perceived risk factors of exertional heat exhaustion-related symptoms in male collegiate athletes in Japan: a case-control study

The purpose of this study was to investigate associations between lifestyle habits, health factors, athletic activity conditions, and exertional heat exhaustion (EHE)-related symptoms among male college athletes in Japan based on a self-completed questionnaire. The paper-based questionnaires were distributed to 11 universities in Japan, and 2006 respondents completed the survey. Data of personal characteristics (age, body mass), lifestyle habits (sleep duration, use of air-conditioner while sleeping, and practice duration), perceived health factors (loss of appetite, sleep deprivation, sickness, dehydration, accumulated fatigue, and mental stress), perceived athletic activity (insufficient rest breaks, high ambient temperature, excessive humidity, strong solar radiation, lack of ambient wind, and clothing discomfort), and EHE-related symptoms (dizziness, headaches, nausea, and malaise) were collected. The association between lifestyle habits, health factors, athletic activity conditions (explanatory variables), and EHE-related symptoms (objective variables) was analyzed using the partial-proportional odds model. "Perceived dehydration" (odds ratios [ORs] 1.70-2.31, p < 0.002)," "sickness" (ORs 1.35-1.76), p < 0.001), "perceived accumulated fatigue" (ORs 1.13-1.31, p ≤ 0.001), "perceived mental stress" (ORs 1.17-1.31, p < 0.019), "lack of ambient wind" (ORs 1.12-1.19, p < 0.022), "loss of appetite" (ORs 1.16-1.23, p < 0.037), and "sleep deprivation" (ORs 1.15-1.17, p < 0.025) were positively associated with EHE-related symptoms, whereas "using an air conditioner during sleeping" (ORs 0.91, p = 0.047) during summer seasons was negatively associated. These findings suggest that athletes should be allowed to postpone or downregulate exercise intensity and/or volume based on their perceptions of dehydration, sickness, accumulated fatigue, mental stress, loss of appetite, and/or sleep deprivation in the summer to prevent heat illness.

The relationship between cricket participation, health and wellbeing: A scoping review

Summarising and synthesising the evidence on cricket health and wellbeing can help inform cricket stakeholders and navigate future research directions. The purpose of this study was to investigate the relationship between cricket participation, health and wellbeing at all ages and playing standards, and identify research gaps in the existing literature. A scoping review was performed from inception to March, 2020. Studies were included if they assessed a construct related to health and/or wellbeing in cricketers, available in English. 219 articles were eligible. Injury incidence per 1,000 player exposures ranged from 1.8-5.7 injuries. 48% of former cricketers experienced persistent joint pain. However, former cricketers reported greater physical activity levels and mental-components of quality of life compared to the general population. Heat injury/illness and skin cancer are concerns and require further research. Cricket participation is associated with an inherent injury risk, which may have negative implications for musculoskeletal health in later life. However, cricket participation is associated with high quality of life which can persist after retirement. Gaps in the literature include prospective studies on health and wellbeing of cricketers, female cricketers, injury prevention strategies, and the impact of cricket participation on metabolic health and lifetime physical activity.

Factors Affecting Incidence Rate of Exertional Heat Illnesses: Analysis of 6 Years of High School Football Practices in North Central Florida

Background

Although experts have advocated for regionally specific heat safety guidelines for decades, guidelines have not been universally adopted.

Purpose

To describe the rate and risk factors associated with exertional heat illness (EHI).

Study Design

Descriptive epidemiology study.

Methods

For a 3-month period (August-October) over 6 years (2013-2018), athletic trainers at 13 high schools in North Central Florida recorded varsity football practice time and length, wet-bulb globe temperature (WBGT), and incidences of EHI, including heat stroke, heat exhaustion, and heat syncope.

Results

Athletes sustained 54 total EHIs during 163,254 athlete-exposures (AEs) for the 3-month data collection periods over 6 years (incidence rate [IR], 3.31 /10,000 AEs). Heat exhaustion accounted for 59.3% (32/54), heat syncope 38.9% (21/54), and heat stroke 1.9% (1/54) of all EHIs recorded. Of the EHIs, 94.4% (51/54) were experienced within the first 19 practices. The first 19 practices had an IR of 7.48 of 10,000 AEs, and the remaining 44 practices had an IR of 0.32 of 10,000 AEs, demonstrating that the risk of EHI for practices 1 to 19 was 23.7 times that of the remaining practices. When comparing morning to afternoon practices, 35.2% (19/54) EHI incidents occurred during morning practices. The risk of EHI during practices with WBGT >82°F (27.8°C) was 3.5 times that of practices with WBGT <82°F.

Conclusion

In the current study, the risk of EHI was greatest in the first 19 practices of the season and during practices with WBGT >82°F. As modifiable risk factors for EHI, increased vigilance and empowerment to adhere to acclimatization guidelines can mitigate EHI risk. Health care providers must continue to advocate for implementation of regulations and the authority to make decisions to ensure patient safety.

American Football Players in Preseason Training at Risk of Acute Kidney Injury Without Signs of Rhabdomyolysis

OBJECTIVE

This study was designed to identify changes in blood biomarkers that would indicate excessive muscle breakdown during the initial 10 days of preseason training in collegiate American football players and subsequently increase their risk of acute kidney injury (AKI).

DESIGN

Prospective cohort study.

SETTING

Preseason, heat acclimatization period.

PARTICIPANTS

Twenty-five Division I American football players.

INTERVENTION

Clinical biomarkers for muscle damage were measured during a preseason training camp. Samples were obtained before camp and approximately 5 and 10 days into camp after completion of heat acclimatization training.

MAIN OUTCOMES

Creatine kinase, myoglobin, lactate dehydrogenase, and creatinine were measured. Glomerular filtration rate (GFR) was calculated. Urine was collected at each blood draw to qualitatively identify hematuria and red blood cells.

RESULTS

A high percentage of athletes had an asymptomatic reduction in kidney function over the 10-day period. Ten of 23 athletes did have a significant, 31.6%, mean reduction in GFR, placing each at risk of AKI according to Risk, Injury, Failure, Loss of kidney function, and End-stage kidney disease (RIFLE) classification. The plasma myoglobin for the at risk of AKI group had a mean value 8× above their baseline mean on day 5 and statistically significant mean 13× higher on day 10 than baseline. The not at risk of AKI group did not have significant differences between days 0, 5, and 10.

CONCLUSIONS

A relatively high percentage of athletes had an asymptomatic reduction in kidney function during the intense preseason training period. 43.4% of athletes in this study had a significant 31.6% mean reduction in GFR over the 10 days. According to RIFLE classification, this placed each athlete "at risk" of AKI.

Individual risk factors associated with exertional heat illness: A systematic review

NEW FINDINGS

What is the topic of this review? Exertional heat illness (EHI) remains a persistent problem for athletes and individuals. This threat remains despite numerous athletic position statements and occupational guidance policies. This review explores primary evidence that demonstrates a direct association between 'known' risk factors and EHI. What advances does it highlight? Primary evidence to support 'known' risk factors associated with EHI is not comprehensive. Furthermore, it is not evident that single individual factors predispose individuals to greater risk. In fact, the evidence indicates that EHI can manifest in non-hostile compensable environments when a combination of risk factors is prevalent.

ABSTRACT

Despite the widespread knowledge of exertional heat illness (EHI) and clear guidance for its prevention, the incidence of EHI remains high. We carried out a systematic review of available literature evaluating the scientific evidence underpinning the risk factors associated with EHI. Medline, PsycINFO, SportDiscus and Embase were searched from inception to January 2019 with no date limitation, with supplementary searches also being performed. Search terms included permutations of risk and heat illness, with only studies in English included. Study selection, data extraction and quality assessment, using the QUALSYST tool, were performed by two independent reviewers. Of 8898 articles identified by the searches, 42 were included in the systematic review as primary evidence demonstrating a link between a risk factor and EHI. The quality scores ranged from 57.50 to 100%, and studies were generally considered to be of strong quality. The majority of risks attributable to EHI were categorized as those associated with lifestyle factors. The findings from the systematic review suggest complex manifestation of EHI through multiple risk factors rather than any one factor in isolation. Further research is needed to explore the accumulation of risk factors to help in development of effective preventative measures.

Regional differences in exertional heat illness rates among Georgia USA high school football players

Many high school associations in recent years are developing policies to improve player safety regarding exertional heat illnesses (EHIs). A question is whether states with diverse climates need multiple sets of guidelines with different activity modification thresholds. We examine this question in the state of Georgia, which has a diverse climate. Our study leverages a multi-year dataset of exertional heat illnesses (EHIs) among high school football players to test the hypothesis that EHI rates under similar wet bulb globe temperatures (WBGTs) will be greater among athletes in the cooler, northern region versus warmer, southern region of the state. The focus of this study is on a 3-year period (2012-2014) when uniform heat safety polices, including acclimatization and activity modification guidelines, were implemented across the state. Results show that athletes in the northern region acclimatize to cooler conditions. Almost 68% of practices have WBGTs < 27.8 °C (82 °F) compared to the southern region where athletes receive many times the exposures to hotter WBGTs in the 27.8-30.5 °C and 30.6-32.2 °C categories. In the post-acclimatization period, we observed statistically significantly (p < .05) greater EHI rates among athletes in the northern region of the state, even when controlling for meteorological conditions. Our findings suggest that differential acclimatization between football players in the northern and southern regions of the state is impacting EHI rates and that regional heat safety guidelines may be needed in Georgia and other states with similarly diverse climates.

Comparison of wet bulb globe temperature measured on-site vs estimated and the impact on activity modification in high school football

Exertional heat stroke is one of the top three causes of death in young athletes, particularly high school football players. Despite evidence that these deaths are completely avoidable with appropriate prevention and treatment, deaths still occur at an alarming rate. Wet bulb globe temperature (WBGT) is the preferred method of both the National Athletic Trainers' Association and American College of Sports Medicine to measure heat intensity. Based on the WBGT, activity modification guidelines (AMG) dictate work-to-rest ratios, activity levels and duration, protective equipment worn, and length and frequency of hydration breaks. Due to the cost of handheld WBGT monitors, smartphone apps that estimate WBGT have been considered an alternative. However, it is unclear how WBGT values estimated by these smartphone apps compare to those measured on-site using handheld WBGT monitors. We compared WBGT values estimated by a commercial smartphone app to those taken on-site at the same time and place. Thirteen athletic trainers measured WBGT in the field during high school football practices over a three-month season in North Central Florida. A paired sample t-test indicated the smartphone app significantly overestimated WBGT (29.0°C ± 4.1°C) compared to on-site measures (26.4°C ± 3.2°C) ( r =0.580; t(943)=-23.38, p <0.0001). The smartphone app-estimated values were consistently greater than on-site measures, resulting in potentially unnecessary activity modifications and cancellations if the app was used in place of on-site handheld WBGT monitors. Despite being significantly cheaper than handheld WBGT monitors, at this time, smartphone apps are not ready for widespread use to guide activity modification decisions.

Expert consensus on the diagnosis and treatment of heat stroke in China

Heat stroke (HS) is a fatal disease caused by thermal damage in the body, and it has a very high mortality rate. In 2015, the People's Liberation Army Professional Committee of Critical Care Medicine published the first expert consensus on HS in China, Expert consensus on standardized diagnosis and treatment for heat stroke. With an increased understanding of HS and new issues that emerged during the HS treatment in China in recent years, the 2015 consensus no longer meet the requirements for HS prevention and treatment. It is necessary to update the consensus to include the latest research evidence and establish a new consensus that has broader coverage, is more practical and is more in line with China's national conditions. This new expert consensus includes new concept of HS, recommendations for laboratory tests and auxiliary examinations, new understanding of diagnosis and differential diagnosis, On-site emergency treatment and In-hospital treatment, translocation of HS patients and prevention of HS.

Compliance With the National Athletic Trainers' Association Inter-Association Task Force Preseason Heat-Acclimatization Guidelines in High School Football

CONTEXT

In 2009, the National Athletic Trainers' Association Inter-Association Task Force (NATA-IATF) released preseason heat-acclimatization guidelines for gradually acclimatizing high school (HS) athletes to the environment during the first 2 weeks of the preseason and reducing the risk of exertional heat illness. However, researchers who studied the 2011 preseason found a low level of overall compliance.

OBJECTIVE

To assess compliance with the NATA-IATF guidelines during the 2017 preseason and compare the findings with 2011 preseason data and between states mandating and not mandating the guidelines.

DESIGN

Cross-sectional study.

SETTING

Preseason HS football, 2017.

PATIENTS OR OTHER PARTICIPANTS

A total of 1023 athletic trainers working with HS football (14.2% response rate).

MAIN OUTCOME MEASURE(S)

Using a survey, we acquired information from athletic trainers on their HS football programs, including location and compliance with 17 NATA-IATF guidelines during the 2017 football preseason. The outcome measures were full compliance with all 17 NATA-IATF guidelines and compliance with ≥10 NATA-IATF guidelines. Prevalence ratios (PRs) with 95% confidence intervals (CIs) compared findings between (1) the 2017 and 2011 preseasons and (2) states whose HS athletic associations imposed a full or partial or no mandate to follow the NATA-IATF guidelines.

RESULTS

Overall, 3.9% reported full compliance with NATA-IATF guidelines; 73.9% complied with ≥10 guidelines. The proportion reporting full compliance was higher in 2017 than in 2011 but not statistically different (3.9% versus 2.5%; PR = 1.54; 95% CI = 0.96, 2.46). However, the proportion reporting compliance with ≥10 guidelines was higher in 2017 (73.9% versus 57.9%; PR = 1.28; 95% CI = 1.20, 1.36). The proportion of respondents reporting their HSs were fully compliant was highest among the with-mandate group (9.4%), followed by the partial-mandate group (4.6%) and the without-mandate group (0.6%). Group differences retained significance when we examined compliance with ≥10 guidelines.

CONCLUSIONS

Although full compliance with NATA-IATF guidelines remained low, many HS football programs complied with ≥10 guidelines.

Activity modification in heat: critical assessment of guidelines across athletic, occupational, and military settings in the USA

Exertional heat illness (EHI) risk is a serious concern among athletes, laborers, and warfighters. US Governing organizations have established various activity modification guidelines (AMGs) and other risk mitigation plans to help ensure the health and safety of their workers. The extent of metabolic heat production and heat gain that ensue from their work are the core reasons for EHI in the aforementioned population. Therefore, the major focus of AMGs in all settings is to modulate the work intensity and duration with additional modification in adjustable extrinsic risk factors (e.g., clothing, equipment) and intrinsic risk factors (e.g., heat acclimatization, fitness, hydration status). Future studies should continue to integrate more physiological (e.g., valid body fluid balance, internal body temperature) and biometeorological factors (e.g., cumulative heat stress) to the existing heat risk assessment models to reduce the assumptions and limitations in them. Future interagency collaboration to advance heat mitigation plans among physically active population is desired to maximize the existing resources and data to facilitate advancement in AMGs for environmental heat.

Examining the Influence of Exercise Intensity and Hydration on Gastrointestinal Temperature in Collegiate Football Players

DeMartini-Nolan, JK, Martschinske, JL, Casa, DJ, Lopez, RM, Stearns, RL, Ganio, MS, and Coris, E. Examining the influence of exercise intensity and hydration on gastrointestinal temperature in collegiate football players. J Strength Cond Res 32(10): 2888-2896, 2018-Debate exists regarding the influence of intensity and hydration on body temperature during American football. The purpose of this study was to observe body core temperature responses with changes in intensity and hydration. Twenty-nine male football players (age = 21 ± 1 year, height = 187 ± 9 cm, mass = 110.1 ± 23.5 kg, body mass index [BMI] = 31.3 ± 5.0, and body surface area [BSA] = 2.34 ± 0.27 m) participated in 8 days of practice in a warm environment (wet bulb globe temperature: 29.6 ± 1.6° C). Participants were identified as starters (S; n = 12) or nonstarters (n = 17) and linemen (L; n = 14) or nonlinemen (NL; n = 15). Variables of interest included core body temperature (T), hydration status, and physical performance characteristics as measured by a global positioning system. Intensity measures of average heart rate (138 ± 9 bpm), low-velocity movement (4.2 ± 1.7%), high-velocity movement (0.6 ± 0.6%), and average velocity (0.36 ± 0.10 m·s) accounted for 42% of the variability observed in T (38.32 ± 0.34° C, r = 0.65, p = 0.01). Hydration measures (percent body mass loss = -1.56 ± 0.80%, urine specific gravity [Usg] = 1.025 ± 0.006, and urine color [Ucol] = 6 ± 1) did not add to the prediction of T (p = 0.83). Metrics of exercise intensity accounted for 39% of the variability observed in maximum T (38.83 ± 0.42° C, r = 0.62, p = 0.02). Hydration measures did not add to this prediction (p = 0.40). Low-velocity movement, high-velocity movement, average velocity, BMI, and BSA were significantly different (p = 0.002, p < 0.001, p = 0.02, p < 0.001, p < 0.001, respectively) between L vs. NL. Heart rate and T were not different between L and NL (p > 0.05). Exercise intensity primarily accounted for the rise in core body temperature. Although L spent less time at higher velocities, T was similar to NL, suggesting that differences in BMI and BSA added to thermoregulatory strain.

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.

Temperate-Water Immersion as a Treatment for Hyperthermic Humans Wearing American Football Uniforms

CONTEXT

  Cold-water immersion (CWI; 10°C) can effectively reduce body core temperature even if a hyperthermic human is wearing a full American football uniform (PADS) during treatment. Temperate-water immersion (TWI; 21°C) may be an effective alternative to CWI if resources for the latter (eg, ice) are unavailable.

OBJECTIVE

  To measure rectal temperature (T_rec) cooling rates, thermal sensation, and Environmental Symptoms Questionnaire (ESQ) scores of participants wearing PADS or shorts, undergarments, and socks (NO_pads) before, during, and after TWI.

DESIGN

  Crossover study.

SETTING

  Laboratory.

PATIENTS OR OTHER PARTICIPANTS

  Thirteen physically active, unacclimatized men (age = 22 ± 2 years, height = 182.3 ± 5.2 cm, mass = 82.5 ± 13.4 kg, body fat = 10% ± 4%, body surface area = 2.04 ± 0.16 m²).

INTERVENTION(S)

  Participants exercised in the heat (40°C, 50% relative humidity) on 2 days while wearing PADS until T_rec reached 39.5°C. Participants then underwent TWI while wearing either NO_pads or PADS until T_rec reached 38°C. Thermal sensation and ESQ responses were collected at various times before and after exercise.

MAIN OUTCOME MEASURE(S)

  Temperate-water immersion duration (minutes), T_rec cooling rates (°C/min), thermal sensation, and ESQ scores.

RESULTS

  Participants had similar exercise times (NO_pads = 38.1 ± 8.1 minutes, PADS = 38.1 ± 8.5 minutes), hypohydration levels (NO_pads = 1.1% ± 0.2%, PADS = 1.2% ± 0.2%), and thermal sensation ratings (NO_pads = 7.1 ± 0.4, PADS = 7.3 ± 0.4) before TWI. Rectal temperature cooling rates were similar between conditions (NO_pads = 0.12°C/min ± 0.05°C/min, PADS = 0.13°C/min ± 0.05°C/min; t₁₂ = 0.82, P = .79). Thermal sensation and ESQ scores were unremarkable between conditions over time.

CONCLUSIONS

  Temperate-water immersion produced acceptable (ie, >0.08°C/min), though not ideal, cooling rates regardless of whether PADS or NO_pads were worn. If a football uniform is difficult to remove or the patient is noncompliant, clinicians should begin water-immersion treatment with the athlete fully equipped. Clinicians should strive to use CWI to treat severe hyperthermia, but when CWI is not feasible, TWI should be the next treatment option because its cooling rate was higher than the rates of other common modalities (eg, ice packs, fanning).

Coaches’ Implementation of the USA Football “Heads Up Football” Educational Program

An integral part of the Heads Up Football (HUF) educational program is the Player Safety Coach (PSC), who is responsible for teaching other coaches within a youth football league about safer blocking/tackling and injury prevention. This study examines the association between youth football coaches’ interactions with the PSC (i.e., attending the PSC clinic at the beginning of the season and seeing the PSC on-field during practices) and their subsequent implementation of the HUF educational program. Data were collected via online questionnaire completed by 1,316 youth football coaches from HUF leagues. Data were analyzed with frequencies and logistic regression. Nearly half of coaches (44.8%) did not attend the PSC clinic; 25.9% reported not seeing their league’s PSC on the field on a regular basis. The lack of PSC on-site presence was significantly associated with worse implementation for “concussion recognition and response,” “heat preparedness and hydration,” and “sudden cardiac event preparedness.” PSC clinic attendance was not associated with implementation. Opportunities exist for improvement in the HUF educational program as there appears to be inconsistent implementation. Further research is warranted to understand how to optimize the role of the PSC in the youth sports context.

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.

A comparison of thermoregulatory responses to exercise between mass-matched groups with large differences in body fat

We sought to determine 1) the influence of adiposity on thermoregulatory responses independently of the confounding biophysical factors of body mass and metabolic heat production (Hprod); and 2) whether differences in adiposity should be accounted for by prescribing an exercise intensity eliciting a fixed Hprod per kilogram of lean body mass (LBM). Nine low (LO-BF) and nine high (HI-BF) body fat males matched in pairs for total body mass (TBM; LO-BF: 88.7 ± 8.4 kg, HI-BF: 90.1 ± 7.9 kg; P = 0.72), but with distinctly different percentage body fat (%BF; LO-BF: 10.8 ± 3.6%; HI-BF: 32.0 ± 5.6%; P < 0.001), cycled for 60 min at 28.1 ± 0.2 °C, 26 ± 8% relative humidity (RH), at a target Hprod of 1) 550 W (FHP trial) and 2) 7.5 W/kg LBM (LBM trial). Changes in rectal temperature (ΔTre) and local sweat rate (LSR) were measured continuously while whole body sweat loss (WBSL) and net heat loss (Hloss) were estimated over 60 min. In the FHP trial, ΔTre (LO-BF: 0.66 ± 0.21 °C, HI-BF: 0.87 ± 0.18 °C; P = 0.02) was greater in HI-BF, whereas mean LSR (LO-BF 0.52 ± 0.19, HI-BF 0.43 ± 0.15 mg·cm(-2)·min(-1); P = 0.19), WBSL (LO-BF 586 ± 82 ml, HI-BF 559 ± 75 ml; P = 0.47) and Hloss (LO-BF 1,867 ± 208 kJ, HI-BF 1,826 ± 224 kJ; P = 0.69) were all similar. In the LBM trial, ΔTre (LO-BF 0.82 ± 0.18 °C, HI-BF 0.54 ± 0.19 °C; P < 0.001), mean LSR (LO-BF 0.59 ± 0.20, HI-BF 0.38 ± 0.12 mg·cm(-2)·min(-1); P = 0.04), WBSL (LO-BF 580 ± 106 ml, HI-BF 381 ± 68 ml; P < 0.001), and Hloss (LO-BF 1,884 ± 277 kJ, HI-BF 1,341 ± 184 kJ; P < 0.001) were all greater at end-exercise in LO-BF. In conclusion, high %BF individuals demonstrate a greater ΔTre independently of differences in mass and Hprod, possibly due to a lower mean specific heat capacity or impaired sudomotor control. However, thermoregulatory responses of groups with different adiposity levels should not be compared using a fixed Hprod in watts per kilogram lean body mass.

Necessity of Removing American Football Uniforms From Humans With Hyperthermia Before Cold-Water Immersion

CONTEXT

The National Athletic Trainers' Association and the American College of Sports Medicine have recommended removing American football uniforms from athletes with exertional heat stroke before cold-water immersion (CWI) based on the assumption that the uniform impedes rectal temperature (T(rec)) cooling. Few experimental data exist to verify or disprove this assumption and the recommendations.

OBJECTIVES

To compare CWI durations, T(rec) cooling rates, thermal sensation, intensity of environmental symptoms, and onset of shivering when hyperthermic participants wore football uniforms during CWI or removed the uniforms immediately before CWI.

DESIGN

Crossover study.

SETTING

Laboratory.

PATIENTS OR OTHER PARTICIPANTS

Eighteen hydrated, physically active men (age = 22 ± 2 years, height = 182.5 ± 6.1 cm, mass = 85.4 ± 13.4 kg, body fat = 11% ± 5%, body surface area = 2.1 ± 0.2 m(2)) volunteered.

INTERVENTION(S)

On 2 days, participants exercised in the heat (approximately 40°C, approximately 40% relative humidity) while wearing a full American football uniform (shoes; crew socks; undergarments; shorts; game pants; undershirt; shoulder pads; jersey; helmet; and padding over the thighs, knees, hips, and tailbone [PADS]) until T(rec) reached 39.5°C. Next, participants immersed themselves in water that was approximately 10°C while wearing either undergarments, shorts, and crew socks (NOpads) or PADS without shoes until Trec reached 38°C.

MAIN OUTCOME MEASURE(S)

The CWI duration (minutes) and T(rec) cooling rates (°C/min).

RESULTS

Participants had similar exercise times (NOpads = 40.8 ± 4.9 minutes, PADS = 43.2 ± 4.1 minutes; t(17) = 2.0, P = .10), hypohydration levels (NOpads = 1.5% ± 0.3%, PADS = 1.6% ± 0.4%; t(17) = 1.3, P = .22), and thermal-sensation ratings (NOpads = 7.2 ± 0.3, PADS = 7.1 ± 0.5; P > .05) before CWI. The CWI duration (median [interquartile range]; NOpads = 6.0 [5.4] minutes, PADS = 7.3 [9.8] minutes; z = 2.3, P = .01) and T(rec) cooling rates (NOpads = 0.28°C/min ± 0.14°C/min, PADS = 0.21°C/min ± 0.11°C/min; t(17) = 2.2, P = .02) differed between uniform conditions.

CONCLUSIONS

Whereas participants cooled faster in NOpads, we still considered the PADS cooling rate to be acceptable (ie, >0.16°C/min). Therefore, if clinicians experience difficulty removing PADS or CWI treatment is delayed, they may immerse fully equipped hyperthermic football players in CWI and maintain acceptable T(rec) cooling rates. Otherwise, PADS should be removed preimmersion to ensure faster body core temperature cooling.

Exertional Heat Illnesses and Environmental Conditions During High School Football Practices

BACKGROUND

Guidelines for preventing exertional heat illnesses (EHIs) during extreme heat stress should be specific to regional environments, age, and sport and should be based on evidence of reducing the risk. Each year in the United States, over 1 million high school football players practice in the August heat; however, no published data describe the incidence of EHIs in these athletes.

PURPOSE

To describe the environmental conditions and incidence of EHIs during high school football practices over a 3-month period.

STUDY DESIGN

Descriptive epidemiology study.

METHODS

For a 3-month period (August-October), athletic trainers at 12 high schools in North Central Florida recorded the practice time and length, environmental conditions (wet-bulb globe temperature), and incidences of EHIs in varsity football athletes.

RESULTS

Athletes suffered 57 total EHIs during 29,759 athlete-exposures (AEs) for the 3-month data collection period (rate = 1.92/1000 AEs). August accounted for the majority of all EHIs, with 82.5% (47/57) and the highest rate (4.35/1000 AEs). Of total heat illnesses, heat cramps accounted for 70.2% (40/57), heat exhaustion 22.8% (13/57), and heat syncope 7.0% (4/57). The odds ratio indicated that athletes in August practices that lasted longer than the recommended 3 hours were 9.84 times more likely to suffer a heat illness than those in practices lasting ≤3 hours.

CONCLUSION

The highest rate of EHIs was during August. Practices in August that exceeded the recommended 3 hours were associated with a greater risk of heat illnesses. The overall rate of EHIs was lower for the high school football athletes observed in the study compared with that reported for collegiate football athletes in the region. The low rates of EHIs recorded suggest that the prevention guidelines employed by sports medicine teams are appropriate for the region and population.

CLINICAL RELEVANCE

Team physicians and athletic trainers should employ evidence-based, region- and population-specific EHI prevention guidelines. Sports medicine teams, coaches, and athletes should be aware of the increased risk of EHIs during August practices and the risk of prolonged practices during August.

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 for Hyperthermic Humans Wearing American Football Uniforms

CONTEXT

Current treatment recommendations for American football players with exertional heatstroke are to remove clothing and equipment and immerse the body in cold water. It is unknown if wearing a full American football uniform during cold-water immersion (CWI) impairs rectal temperature (Trec) cooling or exacerbates hypothermic afterdrop.

OBJECTIVE

To determine the time to cool Trec from 39.5°C to 38.0°C while participants wore a full American football uniform or control uniform during CWI and to determine the uniform's effect on Trec recovery postimmersion.

DESIGN

Crossover study.

SETTING

Laboratory.

PATIENTS OR OTHER PARTICIPANTS

A total of 18 hydrated, physically active, unacclimated men (age = 22 ± 3 years, height = 178.8 ± 6.8 cm, mass = 82.3 ± 12.6 kg, body fat = 13% ± 4%, body surface area = 2.0 ± 0.2 m(2)).

INTERVENTION(S)

Participants wore the control uniform (undergarments, shorts, crew socks, tennis shoes) or full uniform (control plus T-shirt; tennis shoes; jersey; game pants; padding over knees, thighs, and tailbone; helmet; and shoulder pads). They exercised (temperature approximately 40°C, relative humidity approximately 35%) until Trec reached 39.5°C. They removed their T-shirts and shoes and were then immersed in water (approximately 10°C) while wearing each uniform configuration; time to cool Trec to 38.0°C (in minutes) was recorded. We measured Trec (°C) every 5 minutes for 30 minutes after immersion.

MAIN OUTCOME MEASURE(S)

Time to cool from 39.5°C to 38.0°C and Trec.

RESULTS

The Trec cooled to 38.0°C in 6.19 ± 2.02 minutes in full uniform and 8.49 ± 4.78 minutes in control uniform (t17 = -2.1, P = .03; effect size = 0.48) corresponding to cooling rates of 0.28°C·min(-1) ± 0.12°C·min(-1) in full uniform and 0.23°C·min(-1) ± 0.11°C·min(-1) in control uniform (t17 = 1.6, P = .07, effect size = 0.44). The Trec postimmersion recovery did not differ between conditions over time (F1,17 = 0.6, P = .59).

CONCLUSIONS

We speculate that higher skin temperatures before CWI, less shivering, and greater conductive cooling explained the faster cooling in full uniform. Cooling rates were considered ideal when the full uniform was worn during CWI, and wearing the full uniform did not cause a greater postimmersion hypothermic afterdrop. Clinicians may immerse football athletes with hyperthermia wearing a full uniform without concern for negatively affecting body-core cooling.

Pressão por produção e produção de riscos: a “maratona” perigosa do corte manual da cana-de-açúcar

Introdução: o setor sucroalcooleiro vem apresentando franca expansão no país nos últimos anos, contando com cerca de 400 usinas processadoras, mais de 1 mil indústrias de suporte e gerando 1 milhão de empregos diretos. Objetivo: compreender, no trabalho dos cortadores de cana-de-açúcar, os determinantes organizacionais que intensificam a carga de trabalho e afetam a saúde dos trabalhadores. Métodos: utilizou-se a Análise Ergonômica do Trabalho, integrada com a avaliação de aspectos fisiológicos e ambientais. Foram avaliados 40 trabalhadores de uma turma de cortadores escolhida por conveniência. A sobrecarga térmica foi monitorada, bem como a frequência cardíaca e a produção diária de cada trabalhador. Resultados: o corte manual da cana durou em média 8 horas diárias de trabalho, com ritmos intensos, alta frequência de movimentos repetitivos e exigências posturais inadequadas, associadas a condições insalubres. Conclusão: o efeito nocivo das variáveis fisiológicas e do aumento da carga cardiovascular foi demonstrado. O ritmo de trabalho é acelerado por medidas gerenciais e organizacionais, com destaque para o pagamento por produção, responsável pelo aumento do desgaste físico dos trabalhadores, ultrapassando seus limites fisiológicos. Recomenda-se, dentre outras medidas, a alteração na forma de remuneração do trabalho no corte manual de cana.

The secondary school football coach's relationship with the athletic trainer and perspectives on exertional heat stroke

CONTEXT

Prior researchers have examined the first-aid knowledge and decision making among high school coaches, but little is known about their perceived knowledge of exertional heat stroke (EHS) or their relationships with an athletic trainer (AT).

OBJECTIVE

To examine secondary school football coaches' perceived knowledge of EHS and their professional relationship with an AT.

DESIGN

Qualitative study.

SETTING

Web-based management system.

PATIENTS OR OTHER PARTICIPANTS

Thirty-eight secondary school head football coaches (37 men, 1 woman) participated in this study. Their average age was 47 ± 10 years old, and they had 12 ± 9 years' experience as a head football coach.

DATA COLLECTION AND ANALYSIS

Participants responded to a series of online questions that were focused on their perceived knowledge of EHS and professional relationships with ATs. Data credibility was established through multiple-analyst triangulation and peer review. We analyzed the data by borrowing from the principles of a general inductive approach.

RESULTS

Two dominant themes emerged from the data: perceived self-confidence of the secondary school coach and the influence of the AT. The first theme highlighted the perceived confidence, due to basic emergency care training, of the coach regarding management of an emergency situation, despite a lack of knowledge. The second theme illustrated the secondary school coach's positive professional relationships with ATs regarding patient care and emergency procedures. Of the coaches who participated, 89% (34 out of 38) indicated positive interactions with their ATs.

CONCLUSIONS

These secondary school coaches were unaware of the potential causes of EHS or the symptoms associated with EHS, and they had higher perceived levels of self-confidence in management abilities than indicated by their perceived knowledge level. The secondary school football coaches valued and understood the role of the AT regarding patient and emergency care.

Injury rates in professional soccer players during Ramadan

Many of the socio-cultural lifestyle and dietary changes that take place during Ramadan may affect the risk of injury in athletes, but little evidence is available. The aim of the present study was to examine the effects over two consecutive years of the holy month of Ramadan on injury rates in 42 professional players of a Tunisian top-level professional soccer team. Players were retrospectively organized into fasting and non-fasting groups and monitored for 3 months: 4 weeks before Ramadan, during the month of Ramadan (4 weeks), and 4 weeks after Ramadan each year. During Ramadan, training started at 22.00 h. The circumstances (training/match) and mechanism of injury (traumatic/overuse) were recorded. No significant differences between the three periods were observed for weekly mean training load, training strain, training duration, and Hooper's Index (quality of sleep, and quantities of stress, delayed-onset muscle soreness, and fatigue). Compared with non-fasting players, fasters had a lower (P < 0.05) Hooper's Index and stress during and after Ramadan. No significant difference in injury rates was observed between fasting and non-fasting players. Nevertheless, the rates of non-contact (6.8 vs. 0.6 and 1.1) and training overuse (5.6 vs. 0.6 and 0.5) injuries were significantly higher in fasting players during the month of Ramadan than before or after Ramadan. In conclusion, Ramadan, along with the corresponding changes in nutritional habits, sleeping schedule, and socio-cultural and religious events, significantly increased overuse and non-contact injuries in fasting players despite the fact that the training load, strain, and duration were maintained.

Fluid Balance and Dehydration in the Young Athlete

Many young athletes train and compete under conditions that put their body fluid balance at risk, and hypohydration is usually the major concern. Another less frequent condition is hyperhydration that—if accompanied by other risk factors—may cause hyponatremia. Water and electrolyte losses during physical activities occur primarily from sweat. Such losses have been identified mostly in active (but nonathletic) young populations under laboratory settings. Studies have been trying to estimate fluid losses in the athletic population under field conditions, taking into account the sport modality and environmental conditions. Besides these external conditions, young athletes adopt different drinking attitudes, which may depend on knowledge, education, and the opportunities to drink during the break periods as well as fluid availability. Focusing on the young athlete, this review will discuss water and sodium losses from sweat, the effects of hypohydration on performance, and fluid intake attitudes within and during practices and competitions. Some considerations related to the methods of identifying hydration status and guidelines are also given, with the understanding that they should be individually adapted for the athlete and activity. The young athlete, parents, coaches, and athletic/health professionals should be aware of such information to prevent fluid imbalances and the consequent hazardous effects on performance and health.

A retrospective analysis of American football hyperthermia deaths in the United States

Over the period 1980-2009, there were 58 documented hyperthermia deaths of American-style football players in the United States. This study examines the geography, timing, and meteorological conditions present during the onset of hyperthermia, using the most complete dataset available. Deaths are concentrated in the eastern quadrant of the United States and are most common during August. Over half the deaths occurred during morning practices when high humidity levels were common. The athletes were typically large (79% with a body mass index >30) and mostly (86%) played linemen positions. Meteorological conditions were atypically hot and humid by local standards on most days with fatalities. Further, all deaths occurred under conditions defined as high or extreme by the American College of Sports Medicine using the wet bulb globe temperature (WBGT), but under lower threat levels using the heat index (HI). Football-specific thresholds based on clothing (full football uniform, practice uniform, or shorts) were also examined. The thresholds matched well with data from athletes wearing practice uniforms but poorly for those in shorts only. Too few cases of athletes in full pads were available to draw any broad conclusions. We recommend that coaches carefully monitor players, particularly large linemen, early in the pre-season on days with wet bulb globe temperatures that are categorized as high or extreme. Also, as most of the deaths were among young athletes, longer acclimatization periods may be needed.

National athletic trainers' association position statement: preventing sudden death in sports

OBJECTIVE

To present recommendations for the prevention and screening, recognition, and treatment of the most common conditions resulting in sudden death in organized sports.

BACKGROUND

Cardiac conditions, head injuries, neck injuries, exertional heat stroke, exertional sickling, asthma, and other factors (eg, lightning, diabetes) are the most common causes of death in athletes.

RECOMMENDATIONS

These guidelines are intended to provide relevant information on preventing sudden death in sports and to give specific recommendations for certified athletic trainers and others participating in athletic health care.

Policy statement—Climatic heat stress and exercising children and adolescents

Results of new research indicate that, contrary to previous thinking, youth do not have less effective thermoregulatory ability, insufficient cardiovascular capacity, or lower physical exertion tolerance compared with adults during exercise in the heat when adequate hydration is maintained. Accordingly, besides poor hydration status, the primary determinants of reduced performance and exertional heat-illness risk in youth during sports and other physical activities in a hot environment include undue physical exertion, insufficient recovery between repeated exercise bouts or closely scheduled same-day training sessions or rounds of sports competition, and inappropriately wearing clothing, uniforms, and protective equipment that play a role in excessive heat retention. Because these known contributing risk factors are modifiable, exertional heat illness is usually preventable. With appropriate preparation, modifications, and monitoring, most healthy children and adolescents can safely participate in outdoor sports and other physical activities through a wide range of challenging warm to hot climatic conditions.

Football-related injuries among 6- to 17-year-olds treated in US emergency departments, 1990-2007

Football is one of the most popular youth sports in the United States despite the high rate of injuries. Previously published studies have investigated football-related injuries that occurred in organized play but have excluded those that occurred during unorganized play. Through use of the National Electronic Injury Surveillance System database, cases of football-related injuries were identified for analysis. Sample weights were used to calculate national estimates. An estimated 5 252 721 children and adolescents 6 to 17 years old were treated in US emergency departments for football-related injuries. The annual number of cases increased by 26.5% over the 18-year study period. The 12- to 17-year-old age group accounted for 77.8% of all injuries and had nearly twice the odds of sustaining a concussion. The findings suggest the need for increased prevention efforts to lower the risk of football-related injury in children and adolescents.

Exertional heat-related injuries treated in emergency departments in the U.S., 1997-2006

BACKGROUND

Exertional heat-related injuries are a risk to all physically active individuals in warm or hot environments. Unlike classic heat-related injury, exertional heat-related injuries do not require extreme ambient temperatures to cause injury. Still, exertional heat-related injuries, including heat cramps, heat syncope, heat exhaustion, heat stress, and heat stroke, can result in injuries causing a range of outcomes from minimal discomfort to death.

PURPOSE

The purpose of this paper was to describe the epidemiology of exertional heat-related injuries treated in U.S. emergency departments.

METHODS

A retrospective analysis was conducted using data from the National Electronic Injury Surveillance System of the U.S. Consumer Product Safety Commission for all ages from 1997 through 2006. Data provided by the National Electronic Injury Surveillance System were used to calculate national estimates of exertional heat-related injuries. Trends of exertional heat-related injuries over time were analyzed using linear regression.

RESULTS

Nationally, an estimated 54,983 (95% CI=39995, 69970) patients were treated in U.S. emergency departments for exertional heat-related injuries from 1997 to 2006. The number of exertional heat-related injuries increased significantly from 3192 in 1997 to 7452 in 2006 (p=0.002), representing a 133.5% increase. The overall exertional heat-related injury rate per 100,000 U.S. population more than doubled from 1.2 in 1997 to 2.5 in 2006 (p=0.005). Patients aged ≤19 years accounted for the largest proportion of exertional heat-related injuries (47.6%). The majority of exertional heat-related injuries were associated with performing a sport or exercising (75.5%) and yard work (11.0%). The majority of patients (90.4%) were treated and released from the emergency department. Patients aged ≤19 years sustained a larger proportion of sports and recreation exertional heat-related injuries, whereas patients aged 40-59 years and ≥60 years sustained a larger proportion of exertional heat-related injuries from yard work.

CONCLUSIONS

This study confirms that although there is a risk of exertional heat-related injury among all physically active individuals, sports pose a specific risk for people of all ages especially among children and adolescents playing football. Many "everyday" activities such as yard work and home maintenance also pose risks of exertional heat-related injury, particularly to those aged ≥40 years. Further research on risk factors of exertional heat-related injuries during home maintenance and yard work as well as appropriate prevention practices is needed.

Water, hydration, and health

This review examines the current knowledge of water intake as it pertains to human health, including overall patterns of intake and some factors linked with intake, the complex mechanisms behind water homeostasis, and the effects of variation in water intake on health and energy intake, weight, and human performance and functioning. Water represents a critical nutrient, the absence of which will be lethal within days. Water's importance for the prevention of nutrition-related noncommunicable diseases has received more attention recently because of the shift toward consumption of large proportions of fluids as caloric beverages. Despite this focus, there are major gaps in knowledge related to the measurement of total fluid intake and hydration status at the population level; there are also few longer-term systematic interventions and no published randomized, controlled longer-term trials. This review provides suggestions for ways to examine water requirements and encourages more dialogue on this important topic.

Sweat rates, sweat sodium concentrations, and sodium losses in 3 groups of professional football players

CONTEXT

Sweat sodium losses have never been reported in a large cohort of American football players.

OBJECTIVE

To compare sweat rates (SwtRs), sweat sodium concentrations (SwtNa(+)), and sodium losses in 3 groups of players (backs and receivers [BK], linebackers and quarterbacks [LB/QB], and linemen [LM]) to determine if positional differences and, therefore, size differences exist.

DESIGN

Observational study.

SETTING

Data were collected during practices in the second week of 2 consecutive training camps. The wet bulb globe temperature was 78.5 degrees F +/- 3.5 degrees F (25.9 degrees C +/- 1.9 degrees C).

PATIENTS OR OTHER PARTICIPANTS

Eighteen BK, 12 LB/QB, and 14 LM volunteered.

INTERVENTION(S)

Sterile sweat patches were applied to the right forearm after the skin was appropriately cleaned. The patches were removed during practice, placed in sterile tubes, centrifuged, frozen, and later analyzed by flame photometry.

MAIN OUTCOME MEASURE(S)

Sweat rate, SwtNa(+), and sodium loss. We calculated SwtR by change in mass adjusted for urine produced and fluids consumed divided by practice time in hours.

RESULTS

Other than age, physical characteristics were different among groups (P < .001). The SwtR was different among groups (F(2,41) = 7.3, P = .002). It was lower in BK (1.42 +/- 0.45 L/h) than in LB/QB (1.98 +/- 0.49 L/h) (P < .05) and LM (2.16 +/- 0.75 L/h) (P < .01), but we found no differences between SwtRs for LB/QB and LM. The SwtNa(+) was not different among groups (BK = 50 +/- 16 mEq/L, LB/QB = 48.2 +/- 23 mEq/L, and LM = 52.8 +/- 25 mEq/L) and ranged from 15 to 99 mEq/L. Sweat sodium losses ranged from 642 mg/h to 6.7 g/h, and findings for group comparisons approached significance (P = .06). On days when players practiced 4.5 hours, calculated sodium losses ranged from 2.3 to 30 g/d.

CONCLUSIONS

The BK sweated at lower rates than did the midsized LB/QB and large LM, but LB/QB sweated similarly to LM. Sweat sodium concentration and daily sodium losses ranged considerably. Heavy, salty sweaters require increased dietary consumption of sodium during preseason.

The American football uniform: uncompensable heat stress and hyperthermic exhaustion

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 degrees 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 degrees 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.

Thermoregulatory responses and hydration practices in heat-acclimatized adolescents during preseason high school football

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 degrees 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 degrees 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 degrees 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.

Youth sports in the heat: recovery and scheduling considerations for tournament play

One of the biggest challenges facing numerous young athletes is attempting to perform safely and effectively in the heat. An even greater performance challenge and risk for incurring exertional heat injury is encountered when a young athlete has to compete multiple times on the same day, with only a short rest period between rounds of play, during a hot-weather tournament. Within the scope of the rules, tournament directors frequently provide athletes with only the minimum allowable time between same-day matches or games. Notably, prior same-day exercise has been shown to increase cardiovascular and thermal strain and perception of effort in subsequent activity bouts, and the extent of earlier exercise-heat exposure can affect performance and competition outcome. Incurred water and other nutrient deficits are often too great to offset during short recovery periods between competition bouts, and the athletes are sometimes 'forced' to compete again not sufficiently replenished. Providing longer rest periods between matches and games can significantly improve athlete safety and performance, by enhancing recovery and minimizing the 'carryover' effects from previous competition-related physical activity and heat exposure that can negatively affect performance and safety. Governing bodies of youth sports need to address this issue and provide more specific, appropriate and evidence-based guidelines for minimum rest periods between same-day contests for all levels of tournament play in the heat. Youth athletes are capable of tolerating the heat and performing reasonably well and safely in a range of hot environments if they prepare well, manage hydration sufficiently, and are provided the opportunity to recover adequately between contests.

Imersão em água fria para o manejo da hipertermia severa

A incapacidade de dissipar o calor gerado pela atividade muscular prejudica o desempenho e aumenta a predisposição a lesões do organismo. A hipertermia severa induzida pelo esforço físico (HTE) prejudica a saúde e está associada à morbidade e mortalidade de indivíduos em diferentes atividades ocupacionais e atléticas. Estudos sobre a eficiência de métodos de resfriamento corporal têm recomendado a imersão em água fria para o tratamento da HTE. Sua utilização nos minutos iniciais pós-hipertemia parece a melhor recomendação por reduzir o tempo no qual a temperatura central permanece elevada. A manutenção de infraestrutura necessária para a realização desse procedimento deve ser considerada em atividades físicas e condições ambientais nas quais os indivíduos estão mais suscetíveis ao acometimento da HTE. As taxas de resfriamento observadas através da imersão em água a diferentes temperaturas podem servir de referência para o controle da duração do procedimento. Esta revisão analisa a recomendação da imersão em água fria como procedimento de resfriamento corporal para o manejo da HTE.

Medical conditions affecting sports participation

Children and adolescents with medical conditions present special issues with respect to participation in athletic activities. The pediatrician can play an important role in determining whether a child with a health condition should participate in certain sports by assessing the child's health status, suggesting appropriate equipment or modifications of sports to decrease the risk of injury, and educating the athlete, parent(s) or guardian, and coach regarding the risks of injury as they relate to the child's condition. This report updates a previous policy statement and provides information for pediatricians on sports participation for children and adolescents with medical conditions.

Improving health through youth sports: is participation enough?

The health benefits of engaging in regular physical activity are widely known: enhanced cardiorespiratory fitness, increased muscular strength and endurance, and favorable cholesterol and other profiles. Nevertheless, particularly in youth sports programs run by volunteer, and perhaps inadequately trained, coaches, many youth may not realize the health benefits of sports participation due to a number of factors, among them, inappropriate coach-child ratios, limited space, or mismatched expectations between coaches and those of children and their parents. There are specific strategies that can be implemented to ensure that youth receive the maximize benefits from participation in sports. These strategies are presented in the following areas: frequency, intensity, and duration; cross-training or complementary exercise; access points; utilization of space and time; nutrition; and rest. For instance, with regard to the frequency of physical activity, some sports, including soccer, basketball, and singles tennis, require extensive physical effort over an extended period of time, while others, such as baseball and football, have a lot of downtime. Thus, in order for children and youth to meet the recommendation of participating in moderate or vigorous physical activity at least four times per week, sports programs need to have opportunities for all athletes to practice hard. Finally, the author discusses the point at which participation in sports might be too much, leading to significant injuries, frustration, and resentment.

Heat injury prevention practices in high school football

OBJECTIVE

To survey high school American football programs regarding current prevention measures for reducing heat injuries during the football season.

DESIGN

Web-based survey of 27 questions based on consensus statement guidelines by the American College of Sports Medicine on reducing heat injury risk in youth football.

SETTING

National (United States) and community-based.

PARTICIPANTS

High school programs receiving survey distribution from their state athletic association and the National Federation of State High School Associations.

MAIN OUTCOME MEASURES

Responses (percentage and incidence) to questions on preseason acclimatization procedures, practice modification protocols, preparticipation risk factors, hydration management strategies, rest period strategies, heat injury education and policies, and preparation for heat-related emergency care.

RESULTS

A total of 540 high school football programs from 26 states completed the survey. The reported number of preseason heat injuries per program (1.38+/-2.08) was greater (P<0.001) compared to during the regular season (0.98+/-1.84). Programs modified equipment configurations during preseason (no helmets or pads, 31.3%; just helmets, 57.0%; helmets and shoulder pads only, 33.5%) or altered the practice schedule when there was excessive heat. Hydration management, education, and preparation for dealing with an acute heat injury varied among programs.

CONCLUSIONS

Greater implementation of effective prevention measures to reduce the incidence of heat-related injury and death in high school American football is needed. Strategies should focus on modifying practices appropriately on a day-to-day basis to minimize heat strain and optimize hydration, identifying and educating at-risk individuals during the preparticipation period, and developing an emergency action plan for effectively managing heat injuries.

Heat-related illness in athletes

Heat stroke in athletes is entirely preventable. Exertional heat illness is generally the result of increased heat production and impaired dissipation of heat. It should be treated aggressively to avoid life-threatening complications. The continuum of heat illness includes mild disease (heat edema, heat rash, heat cramps, heat syncope), heat exhaustion, and the most severe form, potentially life-threatening heat stroke. Heat exhaustion typically presents with dizziness, malaise, nausea, and vomiting, or excessive fatigue with accompanying mild temperature elevations. The condition can progress to heat stroke without treatment. Heat stroke is the most severe form of heat illness and is characterized by core temperature >104 degrees F with mental status changes. Recognition of an athlete with heat illness in its early stages and initiation of treatment will prevent morbidity and mortality from heat stroke. Risk factors for heat illness include dehydration, obesity, concurrent febrile illness, alcohol consumption, extremes of age, sickle cell trait, and supplement use. Proper education of coaches and athletes, identification of high-risk athletes, concentration on preventative hydration, acclimatization techniques, and appropriate monitoring of athletes for heat-related events are important ways to prevent heat stroke. Treatment of heat illness focuses on rapid cooling. Heat illness is commonly seen by sideline medical staff, especially during the late spring and summer months when temperature and humidity are high. This review presents a comprehensive list of heat illnesses with a focus on sideline treatments and prevention of heat illness for the team medical staff.

Activation of the central cholinergic pathway increases post-exercise tail heat loss in rats

The aim of this study was to evaluate the effects of stimulation of the central cholinergic pathway on the regulation of post-exercise tail heat loss in rats. Either 2.0microL of 25x10(-3)M physostigmine (Phy) or 0.15M NaCl solution (Sal) were injected into the right lateral cerebral ventricle of both resting (n=8) and post-exercising rats (n=6; 24mmin(-1); 25min; 5% inclination). Tail temperature (Ttail) was measured using a thermistor taped to the tail, and intraperitoneal temperature, an index of core temperature (Tc), was recorded using a telemetry sensor implanted into the peritoneal cavity. In resting rats, Phy induced an increase in both Ttail (26.8+/-0.3 degrees C Phy versus 25.2+/-0.6 degrees C Sal; P<0.05) and in heat loss index (0.26+/-0.03 Phy versus 0.14+/-0.05 Sal; P<0.05; 30min after injection), and a decrease in Tc compared to the Sal injection group (36.6+/-0.2 degrees C Phy versus 37.0+/-0.2 degrees C Sal; P<0.05). In post-exercising rats, Phy injection attenuated the decrease in both T(tail) (28.3+/-0.8 degrees C Phy versus 26.4+/-0.6 degrees C Sal; P<0.05) and heat loss index (0.37+/-0.07 Phy versus 0.19+/-0.02 Sal; P<0.05) without altering Tc. We conclude that activation of the central cholinergic pathway increases post-exercise tail heat loss in rats.