1. A2 PE
Thermoregulation

3. Learning Outcomes
• Define thermoregulation and the
body’s four methods of
thermoregulation.
• Explain the importance of the body
maintaining its temperature.

4. Thermoregulation
• What will the man below be experiencing?

5. Thermoregulation
• As with anything the body is affected by
the heat of the environment and
anything else surrounding it.
• The body is able to adjust its own
temperature constantly to keep it in a
safe zone.
• This is called being homeothermic.

6. Thermoregulation
• Body temp fluctuates
from hour to hour by
roughly 1.0 C.
• The normal zone for
the body is 36.1 -
37.8 C.
• Only extreme cold,
heat, illness or
exercise takes the
body out of this ‘safe
zone’.

7. HEAT GAIN HEAT LOSS
METABOLIC
HEAT
ENVIRONMENTAL
HEAT/SOLAR
RADIATION
RADIATION
CONDUCTION
CONVECTION
EVAPORATION
THE SCALES OF BODY TEMPERATURE
SHIVERING
EXERCISE

8. Convection
• As the air is constantly moving around us,
the colder molecules in the air ‘sweep away’
the warm molecules next to our skin.
• This also occurs when the skin is submerged
in water.
• Conduction and Convection together will
account for 10-20% of heat loss.
• This is 26 times more when you’re in water.

9. Conduction
• Conduction is the passing of heat from
one tissue into another it is in contact
with.
• For example, from the muscle to the
skin, from the skin to your clothes or
the air.
• If the air next to the skin is warm as
well, then less of the heat can be
conducted from the skin.

10. Radiation
• The body is constantly giving off heat in the
form of infrared rays.
• At normal room temperature, the nude body
will lose 60% of it’s natural heat in this
manner.
• The body gains the most heat in the same
way. If the environment is warmer than your
skin, your body absorbs the heat.
• If the environment is much colder, the body
loses heat much quicker.

11. Radiation

12. Evaporation
• What happens
when you start
running?

13. Evaporation
• The body moves water
to the surface of the
skin where it can
evaporate and carry the
heat off the body.
• At rest – 20%
• Active – 80%
• If the water doesn’t
evaporate, very little
heat is lost and most is
reabsorbed.
• Don’t remove sweat
with a towel!

14. Humidity
• Which of the four methods of
thermoregulation allows the most heat
to be removed from the body?
• Evaporation.
• The more water molecules that are
already in the air, the less moisture can
evaporate.

15. Humidity
• Where are you
likely to feel the
most sweaty??
• The Dubai or
Singapore?
• 2 minutes

16. Humidity
• The dry hot air of Dubai would allow the
sweat to evaporate almost immediately,
whereas the moist air of the Singapore
would not allow much heat to be lost
through evaporation, causing the body
to continue sweating.
• What problems could both of these
situations cause?

17. Thermoregulation in Sport
• The harder the muscles are working,
the more heat is generated.
• The more energy that is being
processed by the body the more heat is
being generated.
• If the environment is warmer than the
body, no heat can be removed from the
body.
• Think Vasodilation/constriction

18. Thermoregulation in Sport
• At the same time, if the environment is too
cold, then heat will be lost too quickly.
• Due to increased or decreased temperature
effects the flow of blood, the contractions of
all the muscles (including the heart) and the
functions of the nervous system.
• Clothing will play a large role in this, as we’ll
see in our experiment next session!

19. Key terms
• Hyperthermia – a condition in which
body temperature is elevated to a very
high level
• Hypothermia – a condition in which
body temperature is lowered to a very
low level
• Hypohydration – a condition in which
there are very low levels of fluid in the
body

20. Surface Area to mass ratio
• Small children lose temp quicker than
large people
• Gymnasts, distance runners, jockeys
• V
• Weight lifters, sumo wrestling,
throwers, rugby players

21. What happens in the body?
• Thermoregulatory centre is situated in
the hypothalamus – in the brain
• Receives signals from central and
peripheral receptors
• But what can the body do…..

22. Reactions...in addition to sweat
• Vasoconstriction/dilation
• Exercise in warm climate
– Cardiac output shared between muscles & skin
– Can cause a reduction in cardiac return and as
a consequence SV – effects performance
• Increase in heart rate (Cardiac drift) – but has
a limited effect on performance
•

23. Effect of temp
• Ability to run/cycle for long periods
reduces as temperature increases 11oC
to 21oC to 31oC
• Dehydration – big risk at warm and cold
temps (lost through respiratory system
but also sweat if wearing thick clothing)
– leads to fatigue
• Fluid intake essential - hypohydration

24. Effects of Differing Body
Temperature
• 37 C – Normal Temp.
• 39 C – Severe sweating, fast heart rate
and breathlessness
• 41 C – Fainting, vomiting,
hallucinations
• 43 C – Possible death, serious brain
damage.
• 44 C – Almost certain death

25. Effects of Differing Body
Temperature
• 36 C – Moderate shivering – sleep
temp.
• 34 C – Hypothermia
• 32 C – Hallucinations, extreme
sleepiness and comatose
• 27 C – Approaching death
• 25 C – Death due to irregular heart rate

26. But........
• You do need to be warmer than normal
during sport for the following
advantages......

27. V02MAX
Exercise Time
HeartRate
Exercise Time
HOT
COLD

28. Effects of Heat Increase
• Higher V02 MAX
• Higher heart rate and quicker increase
of heart rate
• But
• Increased blood lactate and quicker
build of lactate.

29. Task
• Alan is a long distance runner who is
used to training in Berkshire. He is
taking part in a race in the south of
Spain in July.
• Explain what will be happening to his
body during the race due to his body’s
activity, the environment and the type
of clothing he’ll be wearing.
• 10 minutes

30. Next Session
• Bring your kit, we’ll be in the gym.
• And you will probably need shower
stuff!

31. Learning Outcomes
• Define and discuss the different types
of body composition methods.
• Explain who these methods would be
useful for.