Altitude riding: "The Effects"
by Ted Nider

 There are several things that you need to think about when you are cycling at high altitudes.

     First, you have to take into consideration the barometric pressure changes due to the increase in altitude. When you increase in altitude there is less pressure in the air that you are breathing.

     Most people think that there is less Oxygen, but the reality is that the Oxygen percentage levels are the same at any altitude in our atmosphere. Why all this talk about pressure? Well, pressure is what makes the oxygen in the air we breath get through membranes in our lungs and into our blood. If there was no pressure in the air we would die instantly. That is exactly what makes climbing Mt. Everest so hard is the lack of pressure in the ambient air that surrounds the climbers that attempt the giant. There is just as much Oxygen at 24,000 feet as there is at sea-level - approximately 20.93%. It is just that the pressure is so low at 24,000 feet that your lungs are just unable to absorb oxygen.

     So when you are cycling at 8000 feet or higher you are experiencing a decrease in the ability to absorb Oxygen. Your power output is sacrificed because your muscles require oxygen to burn carbohydrates and fat for energy. Your body is forced to work harder for similar workloads than it would at sea-level. Respiration is increased due to lower levels of Oxygen in your blood so breathing harder is very common. The body tends to burn more carbohydrates at altitude. Since fat requires more Oxygen to burn than Carbohydrates, the body will primarily burn Carbs at high altitude than fat.

     Some symptoms that exist from altitude sickness are headaches, nausea, dizziness, fatigue, shortness of breath, loss of appetite, or extremely low energy levels. These are all a result of pressure changes and Oxygen absorption. Though they cannot be completely prevented they can be treated.

     Always plan to take it easier when you arrive to altitude. Unless you plan on staying for a long time, you will not completely adapt to the new changes in pressure. In order to adapt to changes in altitude, you must plan to stay for at least a couple of weeks. Your body will sense the lowered ability to absorb and process Oxygen and begin to produce more red blood cells. Red blood cells are what transports Oxygen throughout your body. People who live at altitude tend to have higher concentrations of these cells. This allows them to capture more Oxygen when it is passing through their lung membranes. Drink plenty of water and eat more than you normally consume. Avoid alcohol and tobacco and get plenty of rest. Remember your body is in a constant state of Oxygen debt.

     Another thing that you must take into consideration when you are at high altitudes is that the weather can change rather quickly. If it looks like a fine sunny day on one side of the mountain, it does not necessarily mean that the other side of the hill is just as pleasurable. Always take extra clothing, food, matches, lots of water, and even a cell phone if you have one. You can never be too prepared when traveling into the high country. Be safe and have fun!

References:

Marieb, Elaine N., Human Anatomy and Physiology; Third Edition, Benjamin/Cummings Publishing, 1995