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Altitude - KINESIOLOGY 142 Craig Asmundson ALTITUDE AND...

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KINESIOLOGY 142 Craig Asmundson ALTITUDE AND PERFORMANCE I. PHYSICS OF ALTITUDE Medium altitude - 5000 - 10,000 feet - in relation to athletics, we are concerned with this altitude range High altitude - greater than 10,000 feet. More than 40 million people live and work between 10,000 ft. (3048 meters) and 18,000 ft. (5486 meters). 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. PO 2 in dry ambient air at sea level = .209 X 760 mm Hg = 160 mmHg PO 2 in dry ambient air at 3048 meters (10,000 ft.) = .209 X 510 mm Hg = 107 mm Hg. PO 2 in dry ambient air at summit of Mt Everest - 8848 meters (29,028 ft.) = .209 X 250 mm Hg = 52 mm Hg. Oxyhemoglobin dissociation curve - only a small change in percent saturation of hemoglobin is observed with decreasing PO 2 until an altitude of about 10,000 ft. Measurable negative effects on VO 2 max. have been noted at altitudes as low as 4000 ft. The critical alveolar PO 2 at which an unacclimatized person loses consciousness within a few minutes during acute exposure to hypoxia occurs at an altitude of 23,000 ft. Decreased density of air --> decreased external air resistance --> external work is decreased at altitude in sprint type activities where high velocities are involved. There will also be less air resistance encountered by projectiles. Air temperature decreases linearly by 6.5 o C per 1000 meters of altitude or 2 o C (3 o F) per 1000 ft. Air becomes increasingly dry with increasing altitude --> water loss via respiratory tract is higher at high altitude. Solar radiation - UV radiation is more intense at high altitude --> sunburn, snow blindness Force of gravity is decreased with distance from the earth's center --> higher altitudes should have a favourable effect on jumping and throwing events.
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2 II. IMMEDIATE AND LONGER ADJUSTMENTS TO ALTITUDE HYPOXIA A. Cardiovascular System VO 2 = (HR X SV) X (C a O 2 - C v O 2 ) With increasing altitude, C a O 2 progressively decreases. To compensate, cardiac output initially increases during rest and submaximum exercise due to an increase in heart rate. Over the first week at altitude, cardiac output falls to or below sea level values for the same VO 2 and there is a progressive increase in O 2 extraction --> more efficient method of delivering O 2. The most important long-term adaptation to altitude is an increase in the blood's oxygen carrying capacity. Hemoglobin concentration starts to increase during the first two days at altitude due to a decrease in plasma volume and an increase in RBC production by bone marrow. These hematological changes during acclimatization are dependent on an adequate iron intake In some high altitude natives and well-acclimatized sojourners, hemoglobin concentration may be increased 40 - 50% above normal.
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