Option A : Optimising Physiological Performance

• Normal physiological range for core body temperature


  37 celcius 0.6 +-
• Conduction


  is the transfer of heat from one object to another through direct contact
• convection


  the transfer of heat through air or water movement
• Radiation


  heat loss through transfer of energy waves sent by one object and absorbed by another

  
  

  body absorbs radiant heat energy when the temperature of the environment is higher than skin temperature
• Evaporation


  conversion of sweat from liquid to gas/water vapour

  
  

  maximal evaporative heatless from the body occurs when sweat is vaporised from the skin
• Significance of humidity and wind in relation to body heat loss

  Humidity:

  - dry air receives vaporised sweat readily

  - wet air receives little evaporated sweat because it is already heavily laden with moisture
• Heat Cramps

  Causes: intense/prolonged exercise in the heat, muscle fatigue, sodium loss in sweat

  
  

  Symptoms: pain, involuntary spasms of active muscles. low sodium
• Heat Syncope

  Causes: peripheral vasodilation and pooling of venous blood, hypotension. hypohydration

  
  

  Symptoms: light headedness, partial loss of consciousness, pale, high core temperature
• Heat exhaustion

  Causes: increasing negative water balance

  
  

  Symptoms: fatigue, loss of coordination, dizzy pale, reduced sweating, high core temperature
• Heath Stroke

  Causes: Thermoregulatory failure, dehydration

  
  

  Symptoms: core temp is above 41, lack of sweating, seizures, twitching
• steps to prevent heat related disorders

  Acclimatise: 5 to 10 days

  Rehydrate

  Massage/stretching

  Immediate who body cooling

  adapt activities to climatic constraints
• Heat Acclimatisation

  Perform trading sessions in similar environmental conditions for 5-10 days

  90-100 mins of exercise in heat
• Signs of heat acclimatisation during sub-maximal exercise

  lower HR

  lower core temp

  higher sweat rate
• Homeostasis

  the condition in which the body's internal environment remains relatively constant
• Chronic adaptations to exercise in heat

  - sweat response increases

  - muscle blood flow decreases

  - increased lactic acid

  - increased plasma volume

  - a more dilute sweat composition

  - lower electrolyte loss

  - earlier onset sweating

  - reduced rate of muscle glycogen used
• Shivering

  contractions of skeletal muscles (involuntary)
• Goosebumps

  contractions of erector pili muscle (traps the air you radiate)
• Peripheral vasoconstriction

  decrease in diameter of blood vessels under the skin- more blood at the core
• Non-shivering thermogenesis

  metabolic rate increases
• Exercise in cold

  lower HR

  Increased SV
• Body surface area to body mass ratio

  A larger surface area to body mass ratio makes heat loss easier

  Children have a larger are to mass ratio

  
  

  30 to 40% of heat loss is through the head

  
  

  individuals with greater amount of body fat can retain more heat- more fat less heat loss
• Windchill in heat loss

  wind increases the rate of heat loss (via convection and conduction) because the warmer insulating air layer surrounding the body continually exchanges with the cooler ambient air
• Frostbite

  a medical condition in which localised damage is caused to skin due to heat loss

  
  

  Symptoms: skin is yellow or white, burning sensation, hard
• Hypothermia

  low body temperate (34-35)

  
  

  Symptoms: uncontrollable shivering, slurred speech, drowsiness
• Precautions in exercising in cold

  Clothing

  
  

  1 clo= 0.155m^2 x KW^-1

  
  

  the amount of insulation offered
• Physiological responses to exercise in the cold

  Breath Faster/hyperventilation

  Stroke Volume Increase

  Exercise HR decrease

  Increased central blood volume from peripheral vasoconstriction

  More O2 utilisation
• Swimming in cold water

  the effect of cold water on body heat loss is increased because of greater convective heat loss as water is denser than air
• Metabolic responses to exercise in cold

  higher use of lipids, protein, carbs

  more fuel needed