Case Study, Essay Question 3
Rachel Steinbarger
Liberty University
EXSC 510-B02-Advanced Exercise Physiology
Dr. Caleb Bazyler
February 9, 2021
While attending sporting events athletes and spectators are familiar to various weather conditions
while attending or participating in sporting events. Thermoville Heat has made it known that weather
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EXSC 510-Case Study Essay Question 3
conditions can also affect both athletes and spectators while in an indoor facility. The preoptic-anterior
hypothalamus (POAH) works like a thermostat by initiating an increase in heat production when body
temperature falls and an increase in the rate of the heat loss when body temperature rises (Powers &
Howley). Body temperature is measured by chemical and physical processes. Heat loss from the body
may occur by four processes: (1) radiation, (2) conduction, (3) convection, and/ or (4) evaporation
(Powers & Howley, 2018).
Radiation is heat loss in the form of infrared rays (Powers & Howley, 2018). This involves the
transfer of heat from the surface of one object to the surface of another, with no physical contact being
involved (e.g., sun transferring heat to the earth via radiation) (Powers & Howley, 2018). If an individual
is just sitting in a room, they are losing close to 60% of their body heat via radiation. This is possible
because skin temperature is greater than the temperature of surrounding objects (walls, floors, etc.)
(Powers & Howley, 2018). Radiation isn’t only solely focused on the sun, but you can also receive
radiation on a cloudy day. In short, “radiation is heat transfer by infrared rays and can result in either body
heat loss or heat gain depending on the environmental conditions” (Powers & Howley, 2018).
Conduction is the transfer of heat from the body to the molecules of cooler objects in
contact with its surface (Powers & Howley, 2018). An example of conduction would be a
football player’s body temperature increasing while playing or standing on a turf field. The
amount of heat lost during conduction is infrequent. Heat loss in the conduction process is done
quickly or slowly depending on the skin’s temperature, and the surrounding environment the
body will come into contact with.
Convection is a form of heat loss in which heat is transmitted to either air or water
molecules in contact with the body (Powers & Howley, 2018). In convection heat loss, air or
water molecules are warmed and moved away from the source of the heat and are replaced by
cooler molecules (Powers & Howley, 2018). A swimmer is a great example of this, because
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EXSC 510-Case Study Essay Question 3
while a swimmer is submerged in the water doing laps, their body loses heat at a quicker rate
than if they were floating in the water. Swimming in cool water (water temperatures less than
skin temperature) also results in convection heat loss, in fact, water’s effectiveness in cooling is
about 25 times greater than that of air at the same temperature (Powers & Howley, 2018).
Convection is dependent on the airflow over the person’s skin. Therefore, under calm wind
conditions, cycling at high speeds would improve convection colling when compared to cycling
at slow speeds (Powers & Howley, 2018).
The last form a heat loss is evaporation. Evaporation accounts for approximately 25% of
the heat loss at rest, but under most environmental conditions, it is the most important means of
heat loss during exercise (Powers & Howley, 2018). In shorthand, heat is transferred from the
body to water on the skin which is the beginning of the sweating process. When this water gains
sufficient heat (energy), it is converted to a gas (water vapor), taking the heat away from the
body (Powers & Howley, 2018). This process leads into vapor pressure, which “is the pressure
exerted by water molecules that have been converted to gas (water vapor)” (Powers & Howley,
2018). When the body temperature rises above normal, the nervous system stimulates sweat
glands to secrete sweat into the surface of the skin (Powers & Howley, 2018).
Evaporation of sweat from the skin is dependent on three factors: (1) ambient conditions
(i.e., air temperature and relative humidity), (2) the convective currents around the body, and (3)
the amount of skin surface exposed to the environment (Powers & Howley, 2018). Humidity
plays a huge role; high or low humidity can increase or decrease the role of evaporation. High
relative humidity (RH) reduces the vapor pressure gradient between the skin and the
environment (Powers & Howley, 2018). When there is high humidity, sweat rates will increase
water loss, and in turn evaporation is the process of cooling the skin, not sweating.
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EXSC 510-Case Study Essay Question 3
The Thermoville consultation shows the various ways that heat could have been lost in
the environment last season. Radiation, conduction, convection and evaporation all occurred with
spectator’s and athletes. Radiation occurred last season, because the facility may have been
outside or enclosed but either way the spectators body temperature at rest is losing 60% of its
heat due to radiation. Conduction occurred with the athletes if the field was turf and producing a
higher temperature than the athletes’ body temperature. Convection occurred with the wind that
hit both athletes and spectators. Lastly, evaporation occurred with both the athletes and
spectators because the humidity and athlete’s production on the field. Each of these processes is
an increase in heat loss in an individual that could have happened while at the event.
References:
Powers S.K. & Howley E.T., (2018). Exercise Physiology: Theory and Application to Fitness and
Performance. New York, NY: McGraw Hill Education.
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