W4 - Exercise at Altitude Flashcards
In Olympic Games - Mexico City(1968):
* The Olympic games were held at an altitude of 2,240 m
How were performances affected for various disciplines?
– Marathon? - worse, less O2 in the air, takes longer to complete the marathon
– Long jump? - better performance, less molecules stopping movement, higher take off velocity, reaching higher height
– 200m run? - better performance, less resistance from the air
Explain Boyle’s law
- At a constant temperature, the volume of a gas is inversely proportional to its pressure
- Sea level - average pressure of air
- High pressure - air molecules more densely compressed
- Low pressure (altitude) - molecules more spread out - more air volume needs to be breathed in to get the same amount of o2
Ambient pressure & ambient temperature has a small effect on how air molecules are spaced out
Low pressure and temp = more spaced out molecules in the Douglas bag
Describe the oxygen transport cascade
- Difference between:
○ arterial PO2 and the tissue PO2 at sea level is about 60 mmHg at sea level
○ arterial PO2 decreases to about 42 mmHg and the tissue PO2 drops to 27 mmHg at elevation of 4,300 m (14,108 ft)- The diffusion gradient is responsible for driving the oxygen from the haemoglobin in the blood into the tissues
- Change in arterial PO2 at altitude is a much greater consideration for exercise performance than the small reduction in haemoglobin saturation that occurs in the lungs.
How does the ventilatory system respond to exercise at altitude?
- Increased ventilatory drive at altitude (increased breathing rate)
- Decreased maximum capacity at altitude (oxygen uptake, power output)
- Ventilatory drive is quicker
How is Vo2Max effected in altitude?
What is the minimum Vo2Max a person must have in order to survive at high altitude
If sea level 𝐕O2max is below 50 ml/kg/min, it would be impossible to climb without supplemental oxygen
- At summit Vo2max is 15ml/kg/min - to be able to function at mount Everest, the person must have a very good Vo2max at sea-level
What are some drawbacks of being exposed to high altitude for long time periods?
Name a benefit of being exposed to high altitude for a long time period
- Less sleep at altitude so there is less recovery
- Altitude sickness
- Cardiovascular system & aerobic performance is increased, strengthened
What is Erythropoietin?
What does it do?
- A hormone
- Mainly secreted from the kidney cells in response to reduced O2 delivery - when there is hypoxia
- Stimulates erythropoiesis (erythrocyte, or red blood cell production) in the bone marrow(builds more red blood cells)
- Results in increased number of red blood cells - takes a few weeks to do this
○ Greater total blood volume to allows the person to partially compensate for the lower PO2 experienced at altitude
○ Takes weeks to months to fully restore red cell mass. - Polycythaemia - increased red blood cells
Explain respiratory alkalosis
Co2 is in equilibrium with bicarbonate & protons
- This is done when there is a reduced amount of free protons available in the system = a rise in pH
- Reduce pH = Alkalosis
- Respiratory alkalosis - Kidneys excrete more bicarbonate ion to buffer the carbonic acid formed from carbon dioxide.
- Alkalosis is not effective at high altitude
What are acute adaptations to altitude in the blood and plasma?
- Acute: plasma volume ↓ within few hours
– Respiratory water loss, urine production ↑ - Anti-diuretic hormone ↓, renin/aldosterone ↓
→ Lose up to 25% plasma volume
→ Short-term increase in haematocrit 17
What are chronic adaptations to altitude in the blood and plasma?
- Chronic: EPO release from kidneys
→ Red blood cell production in bone marrow ↑
→ Long-term increase in haematocrit
Name the acute adaptations to exercise by the cardiac system
- Acute
– Submaximal heart rate ↑
– Submaximal cardiac output ↑
Name the chronic adaptations to exercise by the cardiac system
- Chronic
– Submaximal heart rate ↑
→ volume loading of heart ↓ (lower volume of blood)
→ stroke volume ↓
– Maximal heart rate ↓ (due to increased parasympathetic tone)
→ can decrease maximal cardiac output - Reduction in β-receptors (in the heart that respond to sympathetic nerve activation, to increase HR
- The lower diffusion gradient to move oxygen from the blood into the muscles
What are the chronic adaptations that muscles undergo to altitude?
- Muscle function and structure changes
– Capillary density ↑ (VEGF)
– Muscle mass loss, possibly protein wasting
→ Cross-sectional area ↓ - Muscle metabolic potential can be affected
– Mitochondrial function and glycolytic enzymes ↓ (some report this, other studies report the opposite)
→ Oxidative capacity ↓
How long does it take to acclimatise to an high altitude environment?
- Acclimation improves performance, but performance may never match that at sea level
- Takes 3-6 weeks at moderate altitude (2,000-3,000 m)
– Add 1 week for every additional 600 m
– Lost within 1 month at sea level
Describe the 2 strategies that athletes can undergo when the live at sea level by compete at high altitude
- Compete ASAP after arriving at altitude
* Does not confer benefits of acclimation
* Adverse effects of altitude not yet kicked in - Train high for 2 weeks before competing
* Worst adverse effects of altitude over
* Aerobic training at altitude not as effective
* Many studies show that many highly trained athletes show no major cardiovascular adaptations and improvements in sea level performance after living and training at altitude
