April 2020 - 20

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WBGT: The Recommended
Measurement for Preventing
Heat Stress Injury & Illness
Exertional heat stress poses a serious risk to people
expected to practice or perform in environments where
hot and humid conditions exist.
There's no question that heat stress remains a top
concern for athletic training professionals. Heat
stress presents many symptoms and encompasses
several heat-induced illnesses such as heat stroke,
heat exhaustion, heat cramps and heat rashes. These
conditions are more likely to occur during hot weather
and the severity of symptoms depends upon the level
of athlete acclimatization and onsite microclimate
conditions, but may also affect athletes in milder
conditions year round. The recommended measurement
used to determine actual environmental heat stress
and assessment for heat stress risk is Wet Bulb Globe
Temperature or " WBGT. "
How is Wet Bulb Globe Temperature
Calculated?
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 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.
Source: http://ksi.uconn.edu/prevention/wet-bulb-globe-temperaturemonitoring/
Athletic
Surfaces & Heat Stress Risk: All Playing
Fields Are Not Created Equal
Weather apps miss the mark when it comes to
providing microclimate data. To assess the real risk of
exertional heat stress, onsite WBGT measurement is
the gold standard for accuracy. There can be multiple
microclimates on a school campus based on the
athletic surfaces and variations in temperature, humidity,
pressure, wind, sun, shade and reflected/radiant heat.
Different types of athletic surfaces result in varying
risk levels of heat stress due to the surface itself and
the impact of external environmental factors. A 2017
study published in the Journal of Athletic Training
shared research findings detailing the disparity between
National Weather Service predictive measurements vs
the actual, observed onsite WBGT measurements of
athletic surfaces.
" WBGT measurements should be taken at
regular intervals on each outdoor athletic playing
surface to adequately capture the environmental
conditions affecting physical performance and
the risk of exertional heat illness. "
Key Study Findings
» Using National Weather Service wet-bulb globe
temperature (WBGT) resulted in heat-safety category
misclassification across all athletic surfaces.
» The National Weather Service WBGT underestimated
the local athletic-surface heat stress, especially
when the surface was black or red or made of
synthetic material.
» Onsite WBGT measurement remains a prudent
choice for determining environmental conditions
and the need for heat-safety physical-activity
modifications or cancellations.
Source:
" The Heat Strain of Various Athletic Surfaces: A
Comparison Between Observed and Modeled Wet-Bulb
Globe Temperatures "
J. Luke Pryor, PhD, ATC, CSCS*†‡; Riana R. Pryor, PhD, ATC*†‡;
Andrew Grundstein, PhD; Douglas J. Casa, PhD, ATC, FNATA, FACSM‡
Journal of Athletic Training; Volume 52, Number 11, November 2017
About Kestrel Instruments
Kestrel Meters are used by athletic trainers and
professionals to monitor the health and safety of the
athletes under their direction. Further, athletic trainers can
set the device to store data at specific time intervals and
then send the information to their smartphones-making
it easier to document, store, and share readings. Trainers
are able to conveniently access pre-programmed zones
for NATA, ASCM and several state athletics guidelines
in the Kestrel 5400 Heat Stress Tracker unit. All of
Kestrel's products are made in the U.S.A and come
with a five-year warranty.
www.heatstress.com
http://ksi.uconn.edu/prevention/wet-bulb-globe-temperature http://www.heatstress.com
April 2020

Table of Contents for the Digital Edition of April 2020
