This is an excellent excerpt reprinted from Burke's book with permission with permission from Human Kinetics, High-Tech Cycling-2nd Edition.

"Human physiology is affected in different ways at high altitude. In general, the various systems of the human body—pulmonary, cardiovascular, endocrine, skeletal muscles—respond and adjust in an effort to provide enough oxygen to survive in the hypoxic environment of high altitude. Some of these life-supporting physiological responses may also enhance athletic performance, particularly in endurance sports.

Hematological
The scientific rationale for using altitude training for the enhancement of aerobic performance is based on the body’s response to changes in the partial pressure of inspired oxygen (PIO2) and the partial pressure of oxygen in the arterial blood (PaO2). PIO2 at sea level is equal to 149 mmHg. At Mexico City (2300 m, 7544 ft), PIO2 drops to approximately 123 mmHg. At the summit of Mt. Everest (8852 m, 29,035 ft), PIO2 is approximately 50 mmHg or only about 30% of sea level PIO2.

If you're planning a triathlon this year in the summer, or in a different location than you are used to, please read this excerpt to plan for the adjustment your body will make. It's an excellent excerpt from John Mora's Triathlon Workout Planner. This excerpt is reprinted with permission.

"Once you know your target zones, you must still do a little tweaking of the range numbers in order to further individualize your training for improved accuracy and efficiency. All training has to be individualized, and these adjustments take into account the different characteristics of each sport, outside conditions, and any illness or overtraining symptoms that