Thermoregulation and Exercise in the Heat and Cold: Difference between revisions
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* Evaporation = heat loss via phase change from liquid to gas | * Evaporation = heat loss via phase change from liquid to gas | ||
** Primary way for heat loss during exercise | ** Primary way for heat loss during exercise | ||
** As body core temperature increases, sweat production increases, sweat turns into vapor when it reaches skin and cooling occurs | |||
** Sweat must evaporate to have cooling effect, dripping sweat provides little or no cooling effect | ** Sweat must evaporate to have cooling effect, dripping sweat provides little or no cooling effect | ||
Revision as of 09:03, 9 March 2023
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Introduction[edit | edit source]
Exercise in the heat or cold can influence the body's ability to regulate body temperature. Although these processes are effective and well-functioning in normal conditions, in extreme hot or cold conditions thermoregulation (regulation of body temperature around a physiological set point) can be inadequate. The human body is able to adapt to these environmental thermal conditions with continued exposure over time. Acclimation refers to the body's short-term adaptations (days/weeks) to these environmental stressors, whereas acclimatisation refers to long-term adaptations (months/ years) to environmental stressors.
Regulation of Body Temperature[edit | edit source]
- Humans are homeothermic - this means that the internal body temperature is physiologically regulated and kept nearly constant despite environmental temperature changes.
- Fluctuations in body temperature are usually no more than 1.0 degrees Celsius (1.8 degrees F)
- Body temperature is a reflection of balance between heat production and heat loss. If this balance is disturbed, this will result in body temperature changes.
- Normal baseline range of body temperature (36.1 to 37.8 degrees C (97.0 - 100.0 degrees F)
- Situations that will cause a change in normal baseline temperatures:
- Fever due to illness
- Extreme conditions of heat or cold
- Prolonged heavy exercise
- Situations that will cause a change in normal baseline temperatures:
Transfer of Heat between Body and Environment[edit | edit source]
- Metabolic heat is produced by active tissues
- Heat moves from the body core (deep within the body) to the body shell (skin) via blood
- When heat reaches the skin it can be dissipated by conduction, convection, radiation and evaporation.
- Maintaining a constant internal body temperature is dependent on the body's ability to balance heat gain (from metabolic processes and the environment) with heat loss. Figure 1. demonstrates this balance: ADD IMAGE
- Heat gain: metabolic heat and environmental heat (conduction, convection, radiation)
- Heat loss: radiation, conduction, convection, evaporation
- Conduction = heat transfer from one solid material to another through direct contact ADD IMAGE
- Example: sitting on cold or hot metal bleachers watching a sports event
- Convection = heat transfer by movement of gas or liquid across a surface
- During movement such as playing sports the air around us passes over the skin and heat is exchanged with air molecules
- Greater movement of air results in greater heat exchange
- Major daily thermoregulatory factor
- Radiation = heat transfer in the form of infrared rays
- The body can give off or receive radiant heat
- Major daily thermoregulatory factor
- Evaporation = heat loss via phase change from liquid to gas
- Primary way for heat loss during exercise
- As body core temperature increases, sweat production increases, sweat turns into vapor when it reaches skin and cooling occurs
- Sweat must evaporate to have cooling effect, dripping sweat provides little or no cooling effect
Challenges with the Transfer of Body Heat[edit | edit source]
- Humidity and heat loss
- High humidity limits evaporation of sweat as the air contains many H2O molecules
- Low humidity provides ideal opportunity for evaporation
- Prolonged sweat evaporation without adequate fluid intake can cause dehydration
- Temperature of skin greater than the temperature of the environment - heat loss through conduction, convection and radiation and evaporation
- Temperature of the environment greater than skin temperature - heat can only be removed through evaporation
- In hot humid situations, evaporation of sweat is limited and convection occurs from the environment to the skin (thus heat is gained)
Thermoregulatory Control[edit | edit source]
Resources[edit | edit source]
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