Altitude and heat

• altitude


  height/elevation above sea level
• humidity


  amount of water vapour in atmospheric air
• barometric pressure


  the pressure exerted by the earth's atmosphere at any given point
• diffusion


  movement of gas down a membrane gradient form an area of high concentration/pressure to an area of low concentration/pressure
• effects on cardiovascular/respiratory system in high altitude


  decreased PO2 in alverlar air

  decreased diffusion gradient to capillary blood

  decreased Hb & O2 association in blood

  decreased O2 transportation to muscle tissue

  decreased diffusion gradient to muscle tissue

  decreased O2 supply for aerobic energy production

  increased F & HR, decreased SV & blood volume

  decreased VO2 max, aerobic capacity, intensity & duration of aerobic performance before fatigue
• Acclimatisation


  A process of gradual adaptation to a change in environment
• Benefits of acclimatisation


  Release of EPO to increase RBC count

  F & ventilation stabilise

  SV & Q reduce

  Reduced altitude sickness, headaches, breathlessness & lack of appetite
• thermoregulation


  process of maintaining internal core temperature
• thermoreceptors


  sensory receptors which sense a change in temperature and relay info to the brain
• if temperature rises

  metabolic heat is transported by circulating blood to the surface of the body and released by sweat
• dehydration


  loss of water in body tissues which impairs the body's ability to thermoregulate so core temperature rises
• hyperthermia


  significantly raised body temperature
• causes of increased body temperature


  high & prolonged exercise intensities

  high air temperature

  high humidity
• consequences of prolonged exercise in the heat


  increased rate of muscular contraction

  metabolic heat produced

  redirectuion of blood flow to skin for cooling

  venous return & rising core temp alter function of proteins so chemical reactions affected
• cardiovascular drift


  upward drift of HR during sustained steady state activity associated with an increase in body temperature
• effect of heat & humidity on cardiovascular system


  1 dilation of arterioles & capillaries to skin - increased blood flow & pooling

  2 decreased blood volume, VR, SV, Q, & BP - increased HR, strain on cardiovascular system, reduced O2 conc
• effect of heat & humidity on respiratory system


  1 dehydration & drying of airways - increased mucus production, constriction of airways, decreased volume of air for gaseous exhange

  2 increased F to maintain O2 consumption - increased O2 cost of exercise

  3 high levels of sunlight increase level of pollutants in air - irritation of airways
• overall effects of thermal strain


  increased O2 cost of exercise

  decreased aerobic energy production

  strength & endurance capacity reduced
• steps to minimise decrease in performance: pre competition

  1 acclimatise to increased temp - increased plasma volume, rate of sweating, efficiency of Q, decreased loss of electrolytes, decreased HR

  2 use of cooling aids to reduce core temp & delay effects of high temps
• steps to minimise decrease in performance: during competition


  pacing strategies to reduce feeling of exertion

  wear clothing that maximises heat loss

  rehydrate as much & as often as possible
• steps to minimise decrease in performance: post competition

  cooling aids to aid return of body temp gradually

  rehydrate using isotonic solutions that replace lost fluids, glucose & electrolytes