1.1d environmental effects on body systems

• altitude

  the height or elevation of an area above sea level
• humidity

  the amount of water vapour in the atmospheric air
• barometric pressure

  the pressure exerted by the earth's atmosphere at any given point
• all gases move down a pressure gradient from an area of high to low partial pressure, diffusing from the alveolar air to the capillary blood and then to the muscle cells. the greater the diffusion gradient, the faster the oxygen will move from one area to another. at rest, the pO2 in the deoxygenated capillary blood arriving back at the alveoli is around 40mmHg. the greater the altitude, the greater the negative impact on the diffusion gradient
• if an athlete competes at high altitude, the rate of oxygen diffusion decreases, reducing haemoglobin saturation, which results in poor transport of oxygen to the muscle tissues for aerobic energy production.
• effects of altitude on cardiovascular and respiratory systems

  • breathing frequency increases both at rest and during exercise to maintain oxygen consumption
  • blood volume decreases as within the first few hours of altitude exposure plasma volume decreases by up to 25% to increase the density of red blood cells in attempt to maximise oxygen transportation
  • stroke volume decreases within the first few hours during sub-maximal exercise, increasing heart rate to maintain cardiac output
  • max cardiac output, stroke volume and heart rate decrease with altitude during maximum intensity exercise
• coaches must prepare the athletes for performance at altitude and allow extra time and practice, increased work:relief ratios, consider more frequent substitutions and supplement oxygen on the sidelines
• acclimatisation

  a process of gradual adaptation to a change in environment (for example, a lower pO2 at altitude)
• acclimatisation guidelines

  • 3-5 days for low altitude (1000-2000m)
  • 1-2 weeks for moderate altitude (2000-3000m)
  • 2+ weeks for high altitude (3000m+) where athletes going above 3000m should sleep no more than 300m higher each day and have regular rest days to prevent altitude sickness
  • 4+ weeks for extreme altitude (5000-5500m) for example, climbers will spend at least one month at base camp before making a summit attempt on Everest
• benefits of acclimatisation

  • release of erythropoietin increases in 3 hours and peaks 24-48 hours after altitude exposure, increasing red blood cell production
  • breathing rate and ventilation stabilise, but remain elevated at rest and during exercise when compared with sea level
  • stroke volume and cardiac output reduce as oxygen extraction is more efficient. after 10 days , cardiac output is lower at any sub-maximal intensity when compared with sea level while heart rate remains elevated
  • there is reduced altitude sickness, headaches, breathlessness, poor sleep and lack of appetite
• erythropoietin

  a naturally produced hormone responsible for the production of red blood cells
• thermoregulation

  the process of maintaining internal core body temperature
• thermoreceptors

  sensory receptors which sense a change in temperature and relay information to the brain
• dehydration

  loss of water in body tissues, largely caused by sweating
• dehydration will impair the body's ability to thermoregulate and core temperature will rise. the rate of heat loss through sweating is affected by humidity; low humidity increases sweating, whereas high humidity decreases sweating and the cooling process
• hyperthermia

  significantly raised core body temperature
• the three highest causes of increased core body temperature in athletes is:

  • high and prolonged exercise intensities
  • high air temperatures
  • high relative humidity

  hyperthermia is common if an athlete pushes themselves too fast, or too long in hot and humid conditions
• during prolonged exercise in the heat, the increased rate of muscular contraction and chemical reactions produce metabolic heat, which may not be removed fast enough to maintain core body temperature, which may cause cardiovascular drift: an upward drift in heart rate associated with a rise in body temperature (1 degree increases heart rate by 10bpm). for exercising athletes the redirection of blood flow to cool skin limits blood flow to the muscles and venous return and the rising core temperature alters the function of proteins such as enzymes, affecting the rate of chemical reactions
• effect of heat, humidity and the bodys thermoregulatory response on the cardiovascular system

  • dilation of arterioles and capillaries to the skin, leading to:
  • increased blood flow and blood pooling in the limbs
  • decreased blood volume, venous return, stroke volume, cardiac output and blood pressure, leading to:
  • increased heart rate to compensate
  • increased strain on the cardiovascular system
  • reduced oxygen transport to the working muscles
• the effect of heat, humidity and the bodys thermoregulatory response on the respiratory system


  • dehydration and drying of the airways in temperatures above 32 degrees makes breathing difficult, leading to:
  • increased mucus production
  • constriction of the airways
  • decreased volume of air for gaseous exchange
  • increased breathing frequency to maintain oxygen consumption, leading to:
  • increased oxygen "cost" of exercise
  • high levels of sunlight increase the effects of pollutants in the air, causing:
  • increased irritation of airways, leading to coughing, wheezing or asthma symptoms
• ways to minimise effects of heat pre competition

  • acclimatise to increased temperatures. 7-14 days of acclimatisation in the same conditions (naturally or in a thermal chamber) increases the body's tolerance to heat by:
  • increasing plasma volume, the onset and rate of sweating, and the efficiency of cardiac output distribution
  • decreasing the loss of electrolytes within sweat, which limits fatigue and cramping
  • decreasing heart rate at a given pace and temperature
  • use of cooling aids such as ice vests to reduce core body temperature and delay the effects of high temperatures and dehydration
• ways to minimise the effects of heat during competition

  • use pacing strategies to alter goals and reduce the feelings of exertion at low-exercise intensities
  • wear suitable clothing that maximises heat loss, removing sweat from the skin rapidly, such as lightweight compression wear
  • rehydrate as often and as much as possible with a hypotonic or isotonic solution that replaces primarily lost fluids but also glucose and the electrolytes lost through the sweat
• ways to minimise the effects of heat post competition

  • cooling aids, such as cold towels and cold fans, aid the return of core body temperature gradually
  • rehydrate using isotonic solutions that replace lost fluids, glucose and electrolytes