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Homeostasis – Is the stable, constant temperature for the
human body to most effectively function. This is around 37
degrees Celsius.
Hypothermia – is the lowering of the core body
temperature to such an extent that the body does not
function normally. This is defined at 35 degrees celcius
Hyperthermia – is the increase of the core body
temperature to such an extent that the body does not
function normally. This is defined at above 37.5 degrees
The body’s response to
 At rest or in extremely cold environments, the body may
be in danger of hypothermia. To combat this the body
increases heat production and decreases heat loss. This
is done through:
1. Vasoconstriction – the narrowing of blood vessels to
decrease flood flow.
2. Vascular adjustment – re-directing blood from the
cooler surface to the warmer core.
3. Muscular activity – shivering is a involuntary response
by the body to increase body temperature.
The body’s response to
 Radiation – by electromagnetic heat waves, the body
gives off heat to surrounding (cooler) objects (no
contact required)
 Conduction – is the transfer of heat from one object to
another through contact.
 Convection – is the transfer of the body’s heat to the
surrounding air (or water).
 Evaporation – Water/sweat vaporising from the body’s
surface or respiratory passageway into the environment.
Factors affecting heat tolerance
 Acclimatisation
 Training Status
 Age
 Gender
 Body Composition
 The body needs time to adjust to warm environments
 Heat acclimatisation refers to the collective
physiologic adaptive changes that improve heat
 Generally, exercising in the first hot days in spring are
the most difficult as the body is not as efficient yet, at
dealing with the warmer environment
Training Status
 Gains for the body’s ability to deal with heat improve
after 8 -12 weeks of training at intensity above 50%
aerobic capacity.
 This is due to body’s sensitivity to begin sweating at
lower core temperatures and increase efficiency in blood
 Athletes who train and compete in hot weather have
great thermoregulatory advantages over those who train
in cooler weather.
 Children are less capable of cooling their body as they
sweat less than adults. This may be due to
underdeveloped peripheral mechanisms.
 Aged adults are less able to respond to the heat due to
delayed onset of sweating and the altered structure of
the skin
 Controversy surround this issue with early studies
indicating that men were better at tolerating exercise in
the heat than women. However conflicting studies have
since shown otherwise. It can be stated that only small
differences surround men and women’s ability to
function in the heat. Any differences include women’s
decrease sweat rate and higher percentage of body fat.
Body Composition
 Body fat acts as an insulator. This will keep heat in the
body and cold out.
 Having increased body fat also results in higher weight
to surface area, making it harder to cool the body.
 Powers, S., K. and Howley, E., T., (2007). Exercise
Physiology: Theory and application to fitness and
performance, sixth edition. McGraw Hill, New York
 McArdle, W. D., Katch, F. I. and Katch V. L., (2007).
Exercise Physiology: Energy, Nutrition and Human
Performance, sixth edition. Lippincott Williams and
Wilkins, Baltimore.