Heat transfers and  hot conditions P1 BND Sport Yr 2
Aims: <ul><li>Last lesson </li></ul><ul><li>We defined key terms and </li></ul><ul><li>Set the basics of thermoregulation....
Task: List different ways  that heat can be transferred.
The transfer of heat <ul><li>4 different ways to lose or gain heat: </li></ul><ul><li>Conduction </li></ul><ul><li>Convect...
Conduction <ul><li>This involves transferring heat directly from one object to another. </li></ul><ul><li>This will not dr...
Convection <ul><li>It involves the movement of air molecules. </li></ul><ul><li>As air molecules moves over a performer’s ...
Radiation <ul><li>Heat is lost to cooler objects around us, e.g. floors, walls etc. </li></ul><ul><li>This is the main met...
Will people with a high % body mass lose more or less than someone with a low % body mass?  Will a tall slim person lose m...
Radiation <ul><li>Someone with a high % body fat will lose less, as the body fat acts as an insulator. </li></ul><ul><li>A...
Evaporation <ul><li>This is the main method of losing heat, e.g. sweating </li></ul><ul><li>As the sweat evaporates from t...
Exercise in the heat <ul><li>As it was highlighted earlier, exercise can increase the metabolic rate. </li></ul><ul><li>It...
Heat loss in hot climates <ul><li>Conduction :  The body’s blood vessels near the surface dilate to allow more blood to th...
Heat loss in hot climates <ul><li>Convection : Heat loss is helped if the air around the performer is moving.  </li></ul><...
Heat loss in hot climates <ul><li>Evaporation:  This is the main way to lose heat.  </li></ul><ul><li>As athletes exercise...
Heat loss in hot climates <ul><li>In order for any of these three methods to work effectively, athletes rely on the circul...
Heat loss in hot climates <ul><li>Heart rate is also raised if the athlete is dehydrated in any way. </li></ul><ul><li>If ...
Heat Transfer when exercising Contracting muscles Solar Radiation; Air temperature Air humidity Evaporation (respiratory) ...
Can you name 3 types of ‘illnesses’ caused by  exercising in hot conditions?
Next week: <ul><li>We will consider these illnesses. </li></ul>
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2010 hot conditions

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2010 hot conditions

  1. 1. Heat transfers and hot conditions P1 BND Sport Yr 2
  2. 2. Aims: <ul><li>Last lesson </li></ul><ul><li>We defined key terms and </li></ul><ul><li>Set the basics of thermoregulation. </li></ul><ul><li>This lesson we will look at : </li></ul><ul><li>The different types of heat transfer. </li></ul><ul><li>How the body can maximise heat loss in hot conditions. </li></ul>
  3. 3. Task: List different ways that heat can be transferred.
  4. 4. The transfer of heat <ul><li>4 different ways to lose or gain heat: </li></ul><ul><li>Conduction </li></ul><ul><li>Convection </li></ul><ul><li>Radiation </li></ul><ul><li>Evaporation </li></ul>
  5. 5. Conduction <ul><li>This involves transferring heat directly from one object to another. </li></ul><ul><li>This will not drastically affect the performer unless they are exercising in cold water. </li></ul><ul><li>In this case, they will lose heat about 25 times quicker than in air. </li></ul>
  6. 6. Convection <ul><li>It involves the movement of air molecules. </li></ul><ul><li>As air molecules moves over a performer’s body, heat will be lost as the air carries heat away. </li></ul><ul><li>Wind will increase the movement of air over the body’s surface, and therefore more heat will be lost. </li></ul><ul><li>Hence why fans are used on hot days, or why a cool breeze is pleasant in hot conditions. </li></ul>
  7. 7. Radiation <ul><li>Heat is lost to cooler objects around us, e.g. floors, walls etc. </li></ul><ul><li>This is the main method of heat loss. </li></ul><ul><li>A person’s body composition, size and mass will decide how much heat is lost through radiation. </li></ul>
  8. 8. Will people with a high % body mass lose more or less than someone with a low % body mass? Will a tall slim person lose more or less heat than a short stocky person
  9. 9. Radiation <ul><li>Someone with a high % body fat will lose less, as the body fat acts as an insulator. </li></ul><ul><li>A tall slim person would lose more heat than a short stocky person. </li></ul><ul><li>In hot countries, the sun gives off heat to the body, which will in turn increase the body’s temperature. </li></ul><ul><li>So exercising in hot countries is difficult, as it is difficult for the body to lose excess heat. </li></ul>
  10. 10. Evaporation <ul><li>This is the main method of losing heat, e.g. sweating </li></ul><ul><li>As the sweat evaporates from the skin’s surface, it produces a cooling effect. </li></ul><ul><li>Humid conditions however, reduce the effectiveness of this method </li></ul><ul><li>Sweat will not evaporate in humid conditions, so no heat is lost. </li></ul>
  11. 11. Exercise in the heat <ul><li>As it was highlighted earlier, exercise can increase the metabolic rate. </li></ul><ul><li>It could also increase the core temperature by 1 °C every 6 minutes if thermoregulation was not happening. </li></ul><ul><li>If an athlete is exercising in a hot country, then they need to optimise heat loss to avoid hyperthermia. </li></ul>
  12. 12. Heat loss in hot climates <ul><li>Conduction : The body’s blood vessels near the surface dilate to allow more blood to the surface. </li></ul><ul><li>The heat from the blood warms the air and any cooler surfaces than it contacts. </li></ul><ul><li>Conduction works together with convection. </li></ul><ul><li>How? </li></ul>
  13. 13. Heat loss in hot climates <ul><li>Convection : Heat loss is helped if the air around the performer is moving. </li></ul><ul><li>If the air around the athlete is still, then it warms up and insulates the performer, reducing heat loss. </li></ul>
  14. 14. Heat loss in hot climates <ul><li>Evaporation: This is the main way to lose heat. </li></ul><ul><li>As athletes exercise they sweat, this cools the skin. </li></ul><ul><li>If the skin is cooled, then it cools the blood as it is carried through blood vessels close to the skin. </li></ul><ul><li>In order for an athlete to use this method of heat dissipation, they must be well hydrated, with adequate levels of salt and electrolytes in their body. </li></ul>
  15. 15. Heat loss in hot climates <ul><li>In order for any of these three methods to work effectively, athletes rely on the circulatory system. </li></ul><ul><li>The blood is redirected to the surface blood vessels, by dilation. </li></ul><ul><li>In very hot conditions, 15-25% of the cardiac output is directed to the skin. </li></ul><ul><li>Thus heart rate increases even further when exercising in hot climates. </li></ul>
  16. 16. Heat loss in hot climates <ul><li>Heart rate is also raised if the athlete is dehydrated in any way. </li></ul><ul><li>If an athlete is dehydrated, then their plasma level is lower. </li></ul><ul><li>A decrease in the amount of plasma causes a decrease in stroke volume. </li></ul><ul><li>Thus the heart rate must increase to maintain the cardiac output. </li></ul>
  17. 17. Heat Transfer when exercising Contracting muscles Solar Radiation; Air temperature Air humidity Evaporation (respiratory) Convection Conduction Evaporation (sweat) Energy metabolism
  18. 18. Can you name 3 types of ‘illnesses’ caused by exercising in hot conditions?
  19. 19. Next week: <ul><li>We will consider these illnesses. </li></ul>

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