D3 - Adaptations of the Body Systems to High Altitude

• After a person has spent a number of weeks at high altitude, their body undergoes a number of changes in order to increase oxygen delivery to cells and improve efficiency of oxygen use.

  This response usually begins immediately and continues for several weeks.

  The adaptations of the body systems to high altitudes include an increase in:

  • Red blood cell production
  • Haemoglobin concentration
  • Capillarisation
  • Mitochondria
  • Oxidative enzymes
• Red Blood Cell Production and Haemoglobin Concentration:

  • The bone marrow contributed to acclimatisation by increasing red blood cell production and therefore the blood haemoglobin concentration.
  •  This increase is triggered by the kidney’s increased production of erythropoietin (EPO). 
  • New red blood cells become available in the blood within four to five days, and have the effect of increasing the blood’s oxygen-carrying capacity.
  • An acclimatised person may have 30-50% more red blood cells than a counterpart at sea level.
• Capillarisation:

  • The cardiovascular system also develops more capillaries in response to altitude. 
  • This has the effect of improving the rate of diffusion of oxygen from the blood into the muscle by shortening the distance between the cells and capillary.
  • All these adaptations in the weeks following exposure are aimed at increasing oxygen transport to the body cells. 
  • This results in a reduction in the cardiac output required for oxygen delivery during rest and exercise compared with pre-acclimatisation.
• Increase in the Number of Mitochondria and Oxidative Enzymes:

  • This increased number of mitochondria and oxidative enzymes appears to be due to the switch in the body’s preferred fuel for energy production. 
  • At low altitude, carbohydrate is the usual energy source, however at altitude fat is the preferred fuel.
  • The change is not well understood, but may be due to the fact that a reduced oxygen supply causes a high lactate level in the muscles and blood stream.
• Increase in the Number of Mitochondria and Oxidative Enzymes:

  • Carbohydrate metabolism also leads to a production of lactate, but fat metabolism does not produce lactate as a by-product.
  • Therefore, the change of the main metabolic fuel from carbohydrate to fat results in reduced level of lactate production.
• Impact of Adaptation on Sport and Exercise Performance:

  Aerobic Performance:

  • The body’s adaptation to high altitude helps significantly, but does not fully compensate for the lack of oxygen in the air.
  • There is a drop in VO2 max by 2% for every 300 m elevation above 1500 m, even after full acclimatisation.
• Impact of Adaptation on Sport and Exercise Performance:

  Anaerobic Performance

  • As the impact of high altitude is mainly due to the reduced amount of oxygen available, and anaerobic performance does not require oxygen, there is limited effect on anaerobic performance at altitude.
  • In fact, due to the reduced partial pressure of air, there is less resistance to movement.
  • This means that some anaerobic performances may be increased if performed at altitude, such as throwing or jumping events.
• Promoting Equivalent Adaptations to High Altitude to Enhance Sport and Exercise Performance at Sea Level:

  • The effects of altitude training will all contribute to higher levels of performance in aerobic endurance events which take place at sea level due to the increased oxygen carrying capacity of the blood and increased ability to deliver the oxygen to the working muscles.
  • This has resulted in types of altitude training being included in elite athletes’ training programmes before significant competitions.
• Promoting Equivalent Adaptations to High Altitude to Enhance Sport and Exercise Performance at Sea Level:

  • However, as living at altitude prevents an athlete from being able to train to such a high intensity as when they are at sea level, because of the reduction in oxygen molecules in the air which results in a reduced VO2 max, altitude training can take different forms.
  • Some athletes acclimatise by training at a low altitude and then sleeping in simulated high altitude in a high altitude chamber.
• Promoting Equivalent Adaptations to High Altitude to Enhance Sport and Exercise Performance at Sea Level:

  • A high altitude chamber replicates the same conditions as being at high altitude with lower partial pressures of gases.
  • This allows the athlete to train at maximal levels when they are at low altitude, and then be exposed to hypoxic stress while sleeping, thus increasing the production of red blood cells and other physiological adaptations.
• Promoting Equivalent Adaptations to High Altitude to Enhance Sport and Exercise Performance at Sea Level:

  • If the person is competing at high altitude, then they may live at high altitude for a number of weeks before the competition, in order for their body to adapt appropriately prior to the competition.
  • They may also sleep and train in a hypoxic chamber before they go to live at high altitude to speed up the process of adaptation.