Chapter 24

Copyright © 2007 Lippincott Williams & Wilkins.

McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth

Edition

Chapter 24

Exercise at Medium and

High Altitude

Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

The Stress of Altitude

• Reduced PO2 creates a metabolic challenge.

• Oxygen transport cascade– Progressive change in environment’s oxygen

pressure and in various body areas

• Oxygen loading at altitude– Saturation of hemoglobin is not influenced

until altitudes of ~ 3,048.


Acclimatization

• Immediate responses to altitude– Hyperventilation– Increased cardiovascular response– Catecholamine response– Fluid loss

• Sensory functions

• Myocardial function


Acclimatization

• Longer term adjustments to altitude– Acid–base readjustment

• Reduced buffering capacity and the “lactate paradox”

– Hematologic changes• Plasma volume decrease

• Polycythemia


Acclimatization

• Longer term adjustments to altitude– Cellular adaptations

• Capillary adjustments

• Increased myoglobin

• Increased mitochondrial density

• Increased 2,3-DPG levels

– Changes in body mass and body composition• Reductions in both lean and fat mass


Acclimatization

• Time required for acclimatization– Depends upon altitude– Acclimatization to a specific altitude doesn’t

ensure acclimatization to a higher altitude.– 2 to 3 weeks after return to sea level,

acclimatization adaptations dissipate.


Metabolic, Physiologic, and Exercise Capacities at Altitude

• Maximal oxygen consumption– Decreases become noticeable at 589 m.– Decreases as altitude increases

• Rate of decrease ~ 7 to 9% per 1,000 m



• Circulatory factors– Lowered max HR and SV are not offset by

higher hemoglobin levels after acclimatization.– Submaximal exercise

• Increased HR offsets decreased SV.

– Maximal exercise• Decreased max HR and SV reduce max cardiac

output.



• Performance measures– Altitude doesn’t influence events lasting less

than 2 minutes.– Events longer than 2 minutes see reduced

performance around 1600 m.– Events longer than 20 minutes see reduced

performance around 600 – 700 m.


Aerobic Capacity on Return to Sea Level

• Possible negative effects– Residual effects of lost muscle mass– Reductions in max HR and SV


Altitude Training and Sea-Level Performance

• Performance upon return is not improved if using

O2max as the criteria

• Altitude acclimatization improves ability to perform at altitude.

• Decrement in absolute training level at altitude– Athletes cannot train as intensely while at altitude.

V


Combine Altitude Stay with Low-Altitude Training

• Live high–train low appears to be the best scenario for improving performance.– Capitalize on stress of altitude and

acclimatization– Train lower so intensity can be maintained


At-Home Acclimatization

• Methods of simulating hypobaric conditions– Cause altitude-induced physiologic adaptations

• Gamow hypobaric chamber

• Wallace altitude tent

Chapter 24

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