Heat

Wet Bulb Globe Temperature or Heat Index?

Yuri Hosokawa, PhD, ATC, Vice President of Education, Vice President of Communication

 

On February 27th, KSI’s Vice President of Education and Communication, Yuri Hosokawa, PhD, ATC was invited to give a presentation on wet bulb globe temperature (WBGT) based activity modification guidelines at the Athletic Trainers’ Society of New Jersey.

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In the CAATE Athletic Training Education Competencies [5th Edition] under the Prevention and Health Promotion section, it is stated that athletic trainers should be able to “explain the principles of environmental illness prevention programs to include acclimation and conditioning, fluid and electrolyte replacement requirements, proper practice and competition attire, hydration status, and environmental assessment (e.g., sling psychrometer, wet bulb globe temperatures [WBGT], heat index guidelines).” That being said, we, as Athletic Trainers and clinicians have all been exposed to the utilization of a sling psychrometer, WBGT, and heat index to monitor and assess environmental heat risk. But do you know the differences in how they work? Without the proper understanding of these indices, you may not be capturing the heat strain appropriately. For example, WBGT of 82°F and heat index of 82°F represent very different environmental conditions because of how these numbers are derived.

To calculate WBGT, you will need: wet bulb temperature (Tw), globe temperature (Tg), and dry bulb temperature (Td). Wet bulb temperature is a measurement of humidity, globe temperature is a measurement for amount of solar radiation, and dry bulb temperature is a measurement for air temperature. In addition, wet bulb temperature and globe temperature are influenced by wind speed. WBGT equation (see bellow) weighs heavily on the Tw (70%) because the air saturation dictates the capacity for the body heat dissipation through sweat evaporation. Since evaporative heat loss accounts for the majority heat dissipation during exercise, an environment that hinders this process will pose an extreme heat strain.

 

WBGT= 0.7Tw + 0.2Tg + 0.1Td

 

On the other hand, heat index is a number that shows “how hot it feels” when relative humidity is factored into the air temperature. It also assumes that the environment is under shade (i.e., not full sunshine) and that the person is walking at 3-mph, which is does not depict the heat stress of someone performing intense exercise in the heat. Therefore, it is apparent that activity modification guidelines that rely on heat index is not appropriate in an athletics context. Lastly, the measurement taken from the sling psychrometer is reflective of the Tw and Td. Typically, a sling psychrometer unit comes with a conversion scale, which allows the clinicians to use the Tw and Td values to calculate the heat index.

Athletic trainers, who are interested in checking or improving current activity modification guidelines, are encouraged to review Table 5 from the NATA Position Statement on Exertional Heat illness, which shows an example from the Georgia High School Athletics Association’s activity modification policy using WBGT.

6th International Conference on the Physiology and Pharmacology of Temperature Regulation

By: William M. Adams, PhD, ATC, Vice President of Sport Safety

 

This past week (December 5-9th), I had the pleasure of representing KSI at the 6th International Conference on the Physiology and Pharmacology of Temperature Regulation. This conference is a biannual conference held in different locations around the world that brings together the world’s leading thermal physiologists to present on topics from a basic (cellular and molecular) level of thermal physiology to clinical and applied applications of that research. This year’s conference was held in Ljubljana, Slovenia, the patron city of Saint George, which is located in the central part of Slovenia.

 

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The meeting started with an in depth discussion on the association of climate change on health. A European-based project, HEAT-SHIELD, was introduced to the audience which is a group tasked with developing guidelines and policies to handle heat stress from various aspects associated with climate change. The development of a well-rounded set of guidelines is needed to address this issue, especially as Europe is seeing the effects of increasing environmental conditions and a large migration of persons from other areas in the world, which when coupled together may cause downstream detrimental effects on health as a whole.

The conference continued with various symposiums, oral presentations and poster presentations on topics related to inflammation and the thermal response, fever, metabolic influences on thermal physiology, and the influence of exercise on thermal physiology. I had the pleasure of presenting some data that I collected examining the influence of hydration on body temperature and heart rate responses during repeated bouts of exercise in the heat. The talk was well received and it prompted some great discussion amongst other physiologists.

 

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It was great being able to meet new friends, connect with others and to discuss future collaborative work with some excellent researchers. The opportunity to attend this conference and to see the beautiful city of Ljubljana was an extremely rewarding experience and I would encourage anyone that does research in this area to attend the 2018 Conference in Split, Croatia.

 

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Be Aware of Heat Stress

By Yuri Hosokawa, MAT, ATC, Director of Communication, Director of Education  

Here in New England, we are starting to see the hint of fall foliage. Fall sports are in the midst of competition and athletes are not afraid to show all the hard work they have put it in throughout the summer months. The weather has cooled down considerably around Storrs, CT during the course of the last few weeks. For example, the forecast for the next few days looks like this in our region.

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Source: weatherwunderground.com Forecast for Storrs, CT. Accessed 10/02/2016.

During pre-season football, we had several days where the ambient temperature was greater than 90-degrees Fahrenheit. I know, I can hear the mind of fellow ATs from the southern states, “we still have days exceeding 90-degrees Fahrenheit and it’s October!

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Source: weatherwunderground.com Forecast for Tampa, FL. Accessed 10/02/2016.

In 2015, Dr. Andrew Grundstein, a professor from the University of Georgia, published a paper that captures this regional differences and proposed activity guideline that takes account of the local climate. In this model, Storrs, CT is classified in Category I, which has the lower threshold to begin activity modification & event cancellation. Tampa, FL is classified in Category III, whose activity guideline closely follow the one developed by the Georgia High School Association that developed the activity guideline based on the heat related injury epidemiology data collected in Georgia.

This regional variance is expected for obvious geographical differences. Therefore, it only makes sense to know and adjust the thermal strain by what’s expected in the region. In other words, what may not be considered a “cancellation level” in the southern states may still be oppressive enough to cancel activities in the northern states, and vice versa.      

Some of you may be wondering, “it is well past beyond pre-season practices and the likelihood of experiencing oppressive heat stress is minimal.” You may be right in that it is less likely. But suppose we experience one day with temperatures exceeding 80-degrees Fahrenheit and »60% humidity in Storrs, CT. This could potentially push the wet bulb globe temperature (WBGT) to rise over 82-degrees Fahrenheit, which warrants considerable activity modification (i.e., maximum practice time 2 hours with increased frequency of rest breaks) in Category I but not necessary in Category III.

(Note: WBGT values should not be used interchangeably with Heat Index or air temperature. View a video from here to learn how these measures are different.)

A well-known example of unexpected weather during the fall is the 2007 Chicago Marathon, where the race organizers made an executive decision to shut down the race after 3.5 hours due to inclement heat (ambient temperature at 88-degrees Fahrenheit).

The 2016 Chicago Marathon is scheduled in less than a week, and as of now, the weather will likely to be cooperating with the runners.

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Source: weatherwunderground.com Forecast for Tampa, FL. Accessed 10/02/2016.

Now, imagine recording highs of 88-degrees Fahrenheit in Chicago, IL (more than 20-degrees higher than what is forecasted for this year’s race), which is a Category II in the 2015 paper. Although there is a limitation in estimating race day WBGT from just the air temperature, it is apparent that recording near 90-degrees Fahrenheit for air temperature, especially around this time of the year for Chicago, is beyond their regional norm. Needless to say, it would affect not only the local runners but other runners who are traveling from all over the world who did not expect the race day to be this oppressive.

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At the end of the day, environmental monitoring is only one of the many tools we have to ensure safety of athletes. Monitoring the wet bulb globe temperature by itself will not protect the athletes per se, but it will give you valuable information for making a better clinical judgment in deciding to modify activity. A great thing about weather conditions is that, at most times, the weather forecast will allow you to make appropriate actions and intervene proactively to remove potential hazards (i.e., moving the event time and/or date, modifying practice intensity and/or duration).

 

#KnowYourCondition

Back in Falmouth

By Yuri Hosokawa, MAT, ATC, Director of Communication and Education

IMG_8657Twenty-seven research and medical volunteers from the Korey Stringer Institute, EC Lee Lab and University of Connecticut joined the 44th New Balance Falmouth Road Race in Falmouth, MA on August 21st. This was the fourth consecutive year in which KSI conducted a field research study at the race in conjunction with working in the medical tent treating exertional heat stroke patients. In this year’s study, we aimed to (1) investigate runner’s knowledge on heat and hydration and behaviors on race day and (2) investigate the use of real time gastrointestinal temperature feedback in altering runner’s behavior during the race. We also assessed participants’ readiness to exercise in the heat by measuring their cardiovascular fitness and their response to heat stress in our environmental chamber.

 

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KSI’s Rebecca Stearns, PhD, ATC and Luke Belval, MS, ATC also spoke at the Medical Symposium hosted by the Falmouth Hospital, which was attended by many medical volunteers and local healthcare professionals. Dr. Stearns’ presentation, The Tale of Two Heat Strokes, introduced case studies of two runners who suffered from exertional heat stroke at the same race with distinctly different prognosis due to the different treatment they received. Belval’s presentation, The Fluid Needs for Today’s Athletes, provided evidence-based suggestions on hydration. At the Health & Fitness Expo, William Adams, PhD, ATC spoke on Optimizing Safety and Maximizing Performance During Running the Heat, which was attended by many runners who were going to be racing the following day.

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We would like to thank the Falmouth Road Race Board of Directors for their continued support and partnership with the Korey Stringer Institute in supporting our mission to educate runners and continue our research in ways to optimize their performance and safety during warm weather road races such as Falmouth Road Race.