Effects of Environment on Performance
Damien Hirst
Alicia Rady
Bonnie Spry
Liam Hawkey
Overview of Lesson
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Basic overview of Theory:
-Thermoregulation
-Physiological Responses to Heat
-Methods of Heat Loss
-Effects of Humidity
Practical Component:
3 Females will be running for 30 minutes at 9km/hr in three
different environmental conditions. These include heated room,
cold room and a neutral conditions.
Everyone will be assigned a job to monitor the effects of the
specific environment
Class Discussion on results will conclude lesson
Thermoregulatory control
• Thermoregulation is based around keeping the body
temperature constant even when the environmental
temperature changes. For this process to be effective
the body needs to keep a balance between heat loss
and heat gain.
• Heat gain comes from environmental heat and metabolic
heat as over 75% of energy from ATP used in
physiological functions is converted into heat. During rest
the majority of heat is lost through radiation and during
exercise the majority is lost through evaporation.
• If this control is successful the body will deviate within
the normal range of 36.1 to 37.8`C.
Thermoregulatory control
• Where and how does all this happen?
• This first starts with sensory receptors called
thermoreceptors located in the skin and brain.
• These thermorecptors detect changes and relay this
information to the region of the brain referred to as the
preoptic-anterior hypothalamus (POAH). In response to
these receptors the hypothalamus activates mechanisms
that regulate heating or cooling of the body.
Thermoregulatory control
• These are the steps involved with hyperthermia
which are outlined in (Wilmore et al., 2008):
• 1. Increased blood and internal temperature
• 2. Increased temperature is sensed by
thermorecptors and relayed to hypothalamus
• 3. Vasodilation occurs in skin blood vessels so
more heat is lost from skin.
• 4. Sweat glands become active, increasing
evaporative heat loss
• 5. Body temperature decreases
Physiological response to heat
• The body experiences physiological responses to heat, these are
even more obvious during exercise. To reduce the effects of muscle
heat production the body reacts in 3 main ways to remain within the
limits of internal body temperature.
• The hypothalamus and various glands sense changes in body heat,
they release hormones or impulses send signals to control the
release heat.
• A circulatory adjustment increases blood flow to the skin and away
from nonessential areas. Blood vessels dilate known as skin
vasolidation which occurs to aid heat dissipation to the environment,
this allows the blood to cool faster.
• Eccrine sweat glands all under the bodies’ skin are triggered by the
hypothalamus to begin to release sweat through a tubular duct onto
the skins surface. The sweat cools if the environmental temperature
is lower then the bodies’, this mechanism of facilitating heat loss
accounts from up to 80% of total heat loss during exercise.
Four methods of heat regulation
• Conduction
• Convection
• Radiation
• Evaporation
Conduction (C)
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Conduction involves the transfer of heat through direct contact with another
solid object.
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Example: When holding a hot cup of coffee in your hand, the heat is
transferred from the cup to your hands from the direct contact, which in turn
warms your hands.
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For conduction to have any effect on core body temperature, the objects
need to be in contact for a prolonged period of time. In terms of the body,
the object needs to be in contact for prolonged period of time so that the
heat can be transferred from the skin to the blood, enabling the heat to
circulate around the body and hence raising core body temperature.
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Conduction is somewhat negligible in sport as contact with other solid
objects is considerably small.
Convection (K)
• Convection involves the transfer of heat via
movement of a gas or liquid across an object,
such as the body(Wilmore et. al, 2008). As the
gas or liquid moves across the object, it either
takes heat away or gives heat to the object.
• Example: When a cool breeze blows across your
face or you dive into a cold body of water, the
molecules move across your body and take the
heat away with them.
Radiation (R)
• Radiation involves the transfer of heat through
electromagnetic (heat) waves from one object to another.
The body gives off such waves to objects around it and
can also receive heat from objects surrounding it that are
warmer. If the temperature of objects around the body
are warmer, the body receives a net heat gain.
• Example: When you open the door to a freezer, you
send electromagnetic (or heat) waves to that freezer. As
The freezers’ temperature is lower than your body
temperature this makes your body cooler.
• At rest, Radiation is the primary method of heat
regulation for the body.
Evaporation (E)
• Evaporation involves the heat loss through the conversion of water
to vapour, such as the liquid sweat.
As the core body temperature rises, so too does sweat production.
However, for sweating to have any effect on heat regulation, the
sweat must evaporate from the skin’s surface.
• Example: When the body temperature rises, sweat is produced in
the form of a liquid. This liquid evaporates from the skin, taking the
heat away with it from the change from liquid to vapor.
• 80% of body heat is lost through evaporation when physically active,
while at rest it is responsible for 10-20% of heat dissipation.
• Humidity has a significant affect of the effectiveness of evaporation
as a mean of heat regulation.
Effects of humidity
• When humidity levels are high the air
contains an increased amount of water
molecules, which decreases the bodies
sweat evaporation.
• When exercising in humid whether it’s
important to:
• Drink plenty of fluids, dress appropriately
and take time to adjust to the environment.
Discussion Question
• Relationship of results based on the
graph?
• Any change in core temperature during the
testing? Why/Why not?
• What physiological mechanisms would
have occurred during the test to control
heat regulation in the hot and cold
conditions?
Conclusion
• What have we learnt about
thermoregulatory control during exercise in
various ambient temperatures?
• What physiological changes occur during
exercise in various ambient temperatures?
• What mechanisms are used to maintain
homeostasis during exercise?