The body maintains a core temperature of 37°C through balancing heat production and heat loss. The hypothalamus acts as the body's thermostat to regulate temperature. Exercise in hot or cold environments can disrupt the body's ability to maintain this temperature balance. Proper hydration is important to avoid heat-related illnesses when exercising in hot conditions. Dehydration of more than 1% body weight can increase core temperature and cause complications.

1. Exercise Physiology 2

2. Temperature Regulation
Normal Body temperature is 37°C. The core of
the body remains at this temperature due to a
balance between heat entering and heat
leaving the body.
HEAT GAIN = HEAT LOSS
Skin temperature is different to body
temperature. It is a product of:
• Environment
• Clothing
• Quantity of body fluid
• Whether at rest or exercise

3. Thermal Death Point
Thermal death point is only 7°C either
side of the body’s “reference”
temperature.

4. Temperature Regulation Control
The hypothalamus is the body’s thermostat. If
the body’s temperature goes above or below
37°C it will react.
The hypothalamus acts as a thermometer
inside of the body. It sends messages to the
heating and cooling systems of the body,
which react to re-establish the normal
internal temperature.

6. Heat balance
HEAT BALANCE
HEAT PRODUCTION HEAT LOSS
Metabolism
Voluntary Exercise
Involuntary Exercise
(shivering)
Radiation
Conduction
Convection
Evaporation
The body loses and gains heat in order to maintain a heat balance.

7. Heat Loss
Radiation – Heat loss through infrared
rays. The greater the difference
between the body’s heat and the
environment, the greater the radiated
heat loss.
Conduction – Transfer of heat through
contact
Convection – Transfer of heat by a
moving fluid (hot air rises)
Evaporation – Sweating

8. Exercise in the heat
When at rest the core body temperature is 37°C.
Muscle temperature however, changes between
25°C and 33°C depending on environmental
temperature. Muscle temperature increases
during exercise.
Exercise in the heat makes it difficult for the body
to maintain it’s heat balance, and the body’s
water requirement greatly increases.
Through perspiration, the body loses its major
cooling aid being water (0.5L to 4.2 L per hour
may be lost.)
Sweating is a result of increased muscle
temperature. Continuous exercise and
inadequate fluid replacement results in rises in
core temperature.
For every 1% loss of body weight there is a 0.1°C
increase in core temperature.

9. Symptoms of water loss
1% loss causes thirst
5% loss causes discomfort
7% loss is dangerous
10% loss results in the breakdown of
coordination and all movements are
difficult.
15% loss results in the athlete
becoming delirious
20% loss is the upper limit of
dehydration before death.

10. DEHYDRATION
•Increase in pulse rate
•Decrease in blood pressure
Decline in circulatory function Increase in core body temperature
•Decrease in blood pressure

11. Heat disorders
1.Dehydration – Excessive loss of water which results in
thirst to circulatory problems to muscle meltdown to
death
2.Heat Cramps – Involuntary cramping of muscle groups
as a result of dehydration
3.Heat Exhaustion – Caused by the inability of the
circulatory system to function properly in the absence of
sufficient water
Warning signs are:
• Profuse sweating
• Paleness
• Fast and shallowing breathing
• Rapid and weak pulse
• Cool and moist skin
• Faintness
• Disorientation

12. What to do:
– Help person to cool off
– Use cool, non-alcoholic beverages
– Rest
– Cool shower, bath or sponge bath
– Lightweight clothing
– Air conditioned room
– If symptoms worsen or last longer than 1 hour seek medical attention
4.Heat Stroke – the temperature regulatory system breaks down
and the core body temperature rises over 41°C within ten to
fifteen minutes
Warning signs are:
– Confusion
– Little or no sweat with red, hot dry skin
– Rapid, strong pulse
– Throbbing headache
– Unconsciousness
– Nausea
What to do:
– Get person to shady or air-conditioned area
– Cool person immediately using whatever methods you can. For example,
immerse in a tub of cool water, cool shower, spray with garden hose or if
humidity is low wrap person in a cool wet sheet and fan them.
– Seek medical assistance as soon as possible

13. Methods for dealing with heat during exercise
• Drink plenty of water
• Replace salt and minerals
• Wear appropriate clothing and
sunscreen
• Schedule outdoor and indoor activities
carefully
• Acclimatisation
• Train with others
• Stay cool indoors
• Monitor those at high risk: infants and
children up to 4 years, people 65 years
of age or older, overweight people, the
ill or those who take medications and
people who overexert during work or
exercise.

14. Exercise in the cold
Dangers of exercising in the cold are
greater than those for exercising in the
heat.
There are only limited means of short-term
acclimatisation to reduce the impact of
cold on exercise performance.
This includes vasoconstriction, which
limits the blood flow to the skin to avoid
cold injury.
Shivering is also a form of gaining heat,
but it can hinder performance as it
fatigues muscle activity and reduces
motor skill level.

15. Methods to reduce the effects of cold while exercising are:
Multiple layers of thin, wind / waterproof, breathable clothing,
which may be adjusted to the level of activity. Remove outside
layers before sweating commences into thin layers. Cover the
head, as it is a very high area of heat loss. Make sure the
extremities are covered to prevent frostbite.
If possible train indoors or in areas away from the wind and
cold temperatures.
Food increases metabolism and digestion increases heat
production. Eat foods containing protein, as it has a high
specific dynamic index (SDA) and makes you warmest out of all
of the types of food.
Must keep the intake of fluids up, as cold air cannot hold
moisture.
Respiration – try to cover the mouth and nose, as cold / dry air
must be warmed / humidified eg wear a scarf
Try to exercise in the middle of the day when the air
temperature is at its highest and when there is the greatest
radiant heat.
If it doesn’t compromise performance, putting on extra fat acts
as insulation against the cold conditions eg Susie Maroney

16. Hypothermia – occurs when the core body
temperature is below 35°C. It is
characterised by the ‘stumbles and
mumbles’.
Results in low blood sugar levels,
hypoventilation, acid / base disturbances,
loss of protein from damaged cells and
eventually cardiac failure
Treatment:
• Remove from cold environment and use dry
clothing
• Slow re-warming – use body heat, drinks and pre-
warmed air
• No hot showers or baths, warm from inside out
and do not massage hands and feet vigorously.

17. Exercise at altitude
Exercise at altitude can have a major effect on
performance
Endurance performance is usually diminished and
anaerobic performance unaffected. This is
because ascent to altitude results in lower
oxygen in inspired air, and therefore less
oxygen delivery to active muscles.
The percentage of oxygen in the air is at the same
at sea level, but the total amount of air is less.
A moderate altitude around 15oom can start to
affect the athlete, and over 5000m can be
extreme.
An increase of altitude results in a decrease of 2°C
per 300m, so the cold also has to be dealt with.

18. Physiological responses to exercise:
Decreased arterial oxygen content
Increased ventilation
Increased CO2 output
Increased stroke volume
Decreased sub-max HR
Decreased VO2 max
Progressive dehydration – increased
breathing of colder / dryer air and
increased urine.

19. Overcoming the effects of altitude
Live high / train low – maximise the resting adaptations to
altitude and minimise the disruption to training caused by
altitude
Daily transit – between high and low altitude
Nitrogen houses – decreases O2 in the air by increasing
nitrogen. Mimic high altitude conditions and you can set the
height you require
Altitude tents – portable and have a decreased O2.
Acclimatisation at Altitude
Adaptations occur over 2 – 3 weeks:Increased red blood cell
concentration – over days due to dehydration and weeks /
months due to increased cell production
Partial restoration of plasma volume
Increased muscle capillarisation
Increased muscle enzyme activity

20. Altitude Sickness
This generally occurs above 3000m and is most likely
to happen in:
–Unacclimatised individuals
–After rapid ascent
–In combination with exercise
Symptoms:
–Headache
–Dizziness
–Nausea
–Sleep disturbances due to cardiovascular responses to
hyperventilation
* Pulmonary / cerebral edema may occur in extreme
circumstances and requires immediate return to lower
altitudes.

21. Hydration
Principles of body temperature regulation
The temperature of a healthy individual is maintained at
around 37°C. Changes in external temperature (eg
weather) or internal temperature (eg exercise or fever)
causes a response in the brain. The hypothalamus in
the base of the brain controls and regulates the
temperature of the body through ‘shivering /
Goosebumps’ to conserve heat accordingly and
‘sweating’ to cool the body. This is called
‘thermoregulation’.
Heat is lost from the body by:
Radiation – heat radiates from the skin to the
environment
Conduction – heat is transferred to an object; seat or
chair for example
Convection – air currents cause heat loss from the skin
Evaporation – sweating causes heat loss

22. Dehydration (loss of fluid from the body)
causes fatigue in a performer so fluid
must be replaced. Continued
dehydration results in an increase in
pulse rate, higher core body
temperature, decreased blood pressure
and a gradual decrease in circulatory
function. Heat cramps and heat stroke
are serious consequences of failure to
hydrate the body sufficiently. Thirst is
not a good indicator as you are already
dehydrated and fluid loss is best
measured by immediate weight loss, for
every 1 kg of weight loss, 1 L of fluid
has been lost. Another indicator of
dehydration is the colour of urine (yellow
usually means dehydrated, clear means
hydrated).

23. Guidelines for fluid replacement
Water is the ideal fluid replacement
Hydrate before a performance
Rehydrate, if possible, during a performance
Drink after the performance
Sports drinks are ok as they aid fluid
absorption, particularly in hot conditions
Wear loose clothing while exercising to help
heat loss from the body
Avoid exercise in the hottest times of the day
and where there is a high fluid loss on two
consecutive days
Avoid alcohol, caffeine and salt as it
accelerates dehydration by absorbing fluids and
making you urinate more.