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By the end of the lesson you will:

  • Be able to explain how temperature affects exercise and sports performance

  • Know how the body regulates body temperature

Effects of High Temp on Performance

Heat... Cramp, stroke or exhaustion?

Stroke

Cramp

  • Muscle spasms caused by heavy sweating.
  • Painful, but does not leave permanent damage.

  • A life-threatening condition and has a high death rate.
  • It occurs because the body has depleted its supply of water and salt, and results in the person’s body temperature rising to dangerous levels. If the core temperature of the body reaches 43 °C or more, the proteins start to break down and change their structure permanently.
  • Once heated to a certain temperature, the structure of the body’s proteins permanently changes and is no longer able to function.

  • As body temp blood flow = sweating

  • The body & muscles compete for blood (carrying O2) & therefore O2 becomes sought after due to the in demand.

  • O2 is needed in the cooling process & the amount of O2 available to vital organs which can lead to health risks & a in performance.

Research the following terms

  • Cramp
  • Stroke
  • Exhaustion

  • Why do they each occur?
  • What are the physiological responses of the body?
  • What are the key differences between them?

Exhaustion

  • Occurs because of dehydration and loss of important minerals thus ’s blood volume so there is not enough blood to supply both the muscles and the skin.
  • This results in the peripheral dilated blood vessels constricting, which significantly reduces heat loss.
  • E.g. If you look at the face of a Caucasian athlete suffering from heat exhaustion, it will suddenly change from a red, rosy appearance to a much paler colour or white

Heat... cramp, stroke or exhaustion?

Effects of High Temperature

Activity- Major Sources of Heat Loss

  • Working in small groups, investigate the likely methods of heat loss for each sport listed below and indicate how each method is likely to work for each sport.

  • Some examples are given for guidance.

The Effect of Temperature and Altitude on Sports Performance

Methods of Heat Loss in

Hot Environments

Learning Outcomes

Controlling our Body Temperature

Body Temperature & it's Effects on the Body

  • Activity- In groups of 4, match the effects of the body when exposed to different temperatures next to the temperature.

  • You have 6 minutes

  • Hypothalamus= body’s thermostat (i.e. controls our body temperature

  • Neurons in the brain regulate our body temp to remain at around 37○

  • Thermal receptor in the skin & the temperature of the blood detect body temp changes & send this information to the hypothalamus.

Measuring Body Temperature

Temperature

What affect can different temperatures have on the body?

Sites on the body

  • mouth, ear or rectum, or under the arm

  • Which is the most common & the most accurate site?

Effects of Low Temp

Low Body Temperature

Physiological Responses to Cold

Responses of the Body to Low Temperature

Shivering

  • A person will experience a rapid involuntary cycle of contraction and relaxation of skeletal muscles, which is called_________.
  • The process of shivering can actually increase the metabolic rate to four to five times above resting levels.

Effects of Low Temp on Performance

Negative

Positive

  • Hypothermia

  • Frostbite in the fingers or toes

  • It happens when a part of the body becomes extremely cold, significantly ’s blood supply to the area, which results in the body tissue freezing.

  • The ice crystals that form rupture & destroy the body’s cells.

  • The region involved turns a deep purple or red colour and has blisters filled with blood.

  • This tissue will then have to be amputated to prevent infection from spreading to other parts of the body.

  • The CV doesn’t have to divert blood to the periphery for heat loss in addition to supplying the exercising muscles with blood.

  • This results in less stress being placed on the heart than when exercising in the heat.

  • Record performances during long-distance running and cycling are usually achieved in cool climatic conditions.

Non-shivering thermogenesis

Three stages to Hypothermia

In your groups identify as many physiological responses to cold as you can - a minimum of 5 please

As an extension - see if your group can explain what the following mean in relation to our body responding to the cold

  • Constriction of the peripheral blood circulation
  • Thermogenesis
  • Shivering

What are the positives and negatives of exercising in the cold?

Effects of Low Temp

  • Can be more harmful than exercising in heat

  • risk of torn muscles & tendons

  • Risk of hypothermia causing fatigue, poor coordination, numbness & disorientation.

  • To maintain core temp the body diverts blood to minimise heat loss

  • Shivering- increases metabolic heat as the muscles vibrate.

  • Piloerection- Goose Bumps!

  • Vasoconstriction- Restricts heat loss from core to skin.

  • Body Size- Increased surface area can increase body heat loss.

  • Body Size- Reduced subcutaneous fat can increase heat loss.

  • in metabolic rate, which is brought about by an release of the hormones thyroxin and adrenaline.

  • An metabolic rate will generate body heat. This process is called non-shivering thermogenesis.

Methods of Heat Loss?

Constriction of the peripheral blood circulation

  • The body the body ↓the blood supply to the peripheral circulation (hands, feet, toes, legs) by constriction of the peripheral blood vessels (vasoconstriction).

  • The purpose of this is to keep the blood close to the body core and redirect it away from the body’s extremities and skin surface, where it would be cooled down by the environment.

  • Vasoconstriction reduces heat loss by up to a third.

  • Subcutaneous fat (under the skin) also aids in maintaining the heat of the blood, as fat is a very good insulator.

Conduction

(Lying head on table)

Convection

(Blowing air over hands)

  • Involves the direct transfer of heat from one object to another.
  • Place your hand on the desk in front of you. How does it feel? If it feels cold, you are losing heat to it via conduction. If it feels hot, you are gaining heat by conduction

  • Method of heat loss is not significant unless a person is exercising in cold water.
  • Water conducts heat away from the body approximately 25 times more quickly than air.
  • At the same temperature, a person in water will lose heat from the body two to four times faster than in air.

Task

  • Blow air over your hand. How does your hand feel? Your hand will probably feel cooler after having air blown over it.
  • This blowing of air molecules across your hand is the basis of convection.

  • As air molecules are moved across the body, heat will be lost because convective air currents carry the heat away.

  • Wind will increase the flow of air over the skin, thus increasing the amount of heat lost through convection.
  • This is why a breeze feels good on a hot day, and why we use fans to help keep us cool.

Evaporation of Sweat

(Major method of heat loss)

Radiation

(Main method of heat loss)

  • Heat is lost (via electromagnetic waves) to cooler objects in the environment, such as the floor, walls, trees, and so on.

  • How much heat a person loses through radiation is determined by their size, mass and body composition.
  • A person with a high body fat percentage will lose less heat through radiation than a person with a low body fat percentage, because body fat acts as an insulator to radioactive heat loss.
  • In contrast, a tall, slim person will lose more heat through radiation than a short, stocky person.
  • In warm climates, the sun radiates heat to the body, which increases its temperature.

  • Heat is transferred continually to the environment as sweat evaporates from the skin surfaces and produces a cooling effect.

  • If the environment is humid, evaporative heat loss is .
  • Heat is only lost when sweat evaporates, which it will not do in humid conditions.
  • Therefore, on a hot, humid day, an athlete can be dripping with sweat, but because the sweat is not evaporating, this does not cool them down.

  • Exercise metabolic rate by 20 to 25 times, and could core temperature by 1 °C every six minutes if heat loss did not take place.

  • Over exposure to hot & humid conditions = hyperthermia = hypothalamus is ineffective

  • There are three major forms of hyperthermia:
  • Heat cramps-
  • Heat exhaustion-
  • Heat stroke-

Core temperature - temperature of the inner body, particularly the organs

  • If the core temperature ’s or ’s by 1°C or more, this will affect an athlete’s physical and mental performance.

Larger changes in core temperature lead to:

  • Hypothermia ( ) Core temp less than 35°C
  • Hyperthermia ( ) in core temp greater than 40°C
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