Effects of Environment on Performance

1
Effects of Environment on Performance

• Damien Hirst
• Alicia Rady
• Bonnie Spry
• Liam Hawkey

2
Overview of Lesson

• 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

3
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
  37.8C.

4
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.

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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

6
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.

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Four methods of heat regulation

• Conduction
• Convection
• Radiation
• Evaporation

8
Conduction (C)

• Conduction involves the transfer of heat through
  direct contact with another solid object.
• 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.
• 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.
• Conduction is somewhat negligible in sport as
  contact with other solid objects is considerably
  small.

9
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.

10
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.

11
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 skins 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.

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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 its important
  to
• Drink plenty of fluids, dress appropriately and
  take time to adjust to the environment.

13
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?

14
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?