Exercise In Extreme Conditions

Question 1

What happens on acute exposure to high altitude?

Answer 1

Lower atmospheric PaO2 causew hypoxaemia. This stimulates the peripheral chemosensors in the carotid bodies to increase ventilation. This response increases over weeks, leading to higher alveolar PaO2 and lower PCO2.

Question 2

What Respiratory factor limits exercise at very high altitudes ?

Answer 2

Work of breathing

Question 3

What effect does altitude have on our cardiovascular system?

Answer 3

Hypoxia causes catecholamines release which increases cardiac output and BP. With acclimatisation this response returns to sea level values after 10 days to 3 weeks.

Question 4

Why should people with pulmonary hypertension not ascend to altitude ?

Answer 4

Hypoxic pulmonary vasoconstriction can make the hypertension worse.

Question 5

What happens to our blood at altitude?

Answer 5

There is an increase in EPO which takes 10- 14 days to have an effect
Levels of haemoglobin above 180 can lead to increased viscosity, impaired microvascular perfusion and impaired oxygen delivery to cells. It can also leas to increased pulmonary vascular resistance leading to pHTN

Question 6

What affect does altitude have on our peripheral vasculature ?

Answer 6

At moderate altitudes there is an increase in capillary density and mitochondria. With prolonged exposure to very high altitudes there is a decrease in muscle fibre size which leads to a relative increase in capillary density and reduced diffusion distance.

Question 7

How do our bodies respond to exercise in heat?

Answer 7

Over a few days there is an increased sweating response and increased blood flow to the skin. After 7-10 days there is a compensatory increase in plasma volume to compensate for the expanded blood flow. This means that exercise capacity increases as there is more blood to go to the muscles, resting HR Decreases and stroke volume increases.

Question 8

How do our bodies react to exercise in the cold?

Answer 8

The first response is to shiver, heavy shivering can increase the metabolic rate up to 5 times the restingvalue and increase heat production for a couple of hours.
Shivering will continue until body temperature drops to 33.3 degrees.

With prolonged cold exposure the shivering response Decreases.