12. Environmental Physiology - Altitude Physiology

Question 1

What is Moderate Altitude?

Answer 1

Moderate altitude –
1500m-3000m (5000 - 10,000 feet) - in relation to athletics, we are concerned with this altitude range.
Whistler Mountain and Mexico City ~ 2200m.

Question 2

What is High Altitude?

Answer 2

High altitude -
greater than 3000m (10,000 ft.). More than 40 million people live and work between 3000m and 5500m (10000 and 18,000 ft.).
Pikes Peak Colorado 4300m.

Question 3

What is Extreme Altitude?

Answer 3

Extreme Altitude –
over 5500m (18000ft)
Mt Everest 8848 m

Question 4

How does Barometric Pressure change as altitude increases?
How does the Chemical Composition Change?

Answer 4

Barometric (air) pressure decreases as altitude increases (ie) as the weight of the column of air above the point of measurement decreases.

However, the chemical composition of the atmosphere is uniform up to 20,000 meters.

Question 5

How does PO2 change at different altitudes?

Answer 5

PO2 in dry ambient air at sea level =
.209 X 760 mm Hg = 160 mmHg

PO2 in dry ambient air at 3048 meters (10,000 ft.) =
.209 X 510 mm Hg = 107 mm Hg.

PO2 in dry ambient air at summit of Mt Everest - 8848 meters (29,028 ft.) =
.209 X 250 mm Hg = 52 mm Hg.

Question 6

Oxyhemoglobin dissociation curve

Answer 6

Oxyhemoglobin dissociation curve - only a small change in percent saturation of hemoglobin is observed with decreasing PO2 until an altitude of about 3000m (10,000 ft).
Measurable negative effects on VO2 max. have been noted at altitudes as low as 1200m
(4000 ft.)

Question 7

How does Air Temperature, Air moisture and Solar Radiation change with altitude?

Answer 7

Air temperature decreases linearly by 6.5o C per 1000 meters of altitude or 2oC (3o F) per
1000 ft.

Air becomes increasingly dry with increasing altitude –> water loss via the respiratory tract is higher at high altitudes.

Solar radiation - UV radiation is more intense at high altitudes –> sunburn, snow blindness

Question 8

How do Density and Gravity change as Altitude changes?

Answer 8

• Decreased density of air
  – Decreased external air resistance and work
• Force of gravity is decreased with distance from the earth’s center
• higher altitudes have a favourable effect on sprinting, jumping and throwing events.

Question 9

How is VO2 max affected by altitude?

Answer 9

• Measurable negative effects on VO2max. have been noted at altitudes as low as 1200m.
  – SFU is approximately 300 m
  – Mt Seymour is 1450 m
• Endurance Athletes may experience declines in VO2 max and effects on performance as low as 580 m.
• The critical alveolar PO2 at which an unacclimatized person loses consciousness within a few minutes during acute exposure to hypoxia occurs at an altitude of 7000m.
  – Airplanes cruising altitude 10000 m