Most people acclimate to high-altitude training in about 10 days.
When training at high altitudes, the human body must adapt to the lower air pressure available, which makes it hard for oxygen to enter the blood and be used by muscles. The body initially responds by increasing its heart rate to get more oxygen throughout the body. Over time, the body will create more red blood cells and capillaries to help produce and carry more oxygen. According to National Outdoor Leadership School Wilderness First Aid Guide, about 80 percent of people are able to adjust after 10 days, and 95 percent are able to acclimatize by six weeks at altitude.
Monitor Nutrition
Higher altitudes will affect the body's appetite and metabolism. Individuals usually experience a decrease in appetite but an increase in metabolism because of the extra work the body must do to carry oxygen throughout the body. Barry Braun of the University of Massachusetts estimates that an individual's metabolism can increase by 100 to 200 calories per day. A loss of appetite and an increase in metabolism can result in insufficient energy, vitamin deficiencies and muscle loss. Individuals should adjust nutrition to maintain sufficient energy when training at altitude. Because of a decrease in the body's ability to use fat as an energy source, a high-carbohydrate diet is suggested. Janet Pidcock of Peak Performance recommends that diets composed of 70 percent carbohydrates are appropriate for high-altitude training.
Hydration Recommendations
Dehydration is common when training at altitude. Cooler air temperatures can lead to less thirst and less sweat levels, resulting in individuals drinking less water. More water vapor is exhaled at altitude because of the increased heart rate and rapid breathing. Drink two to three times more fluid than when training at lower elevations. Minimize alcohol and caffeine during the first few days, as altitude increases the body's sensitivity to alcohol and sedatives.
Sun Protection
Sun rays are much stronger at altitude than at sea level because of the thinner air. Sunburns and skin damage occur easier and more often. When training outside, use sunscreen with both UVA and UVB protection, especially during 11 a.m. and 2 p.m. when the rays are the strongest.
Training Recommendations
Individuals will notice a decrease in their ability to exercise when training at altitude. Dr. Robert Girandola at the University of Southern California estimates that above 5,000 feet, cardiovascular fitness decreases 10 percent to 11 percent for every increase of 3,000 feet. If running an eight-minute mile pace at sea level was 70 percent intensity, then at 8,000 feet it would be an intensity of 80 percent. Reduce your exercise intensity by 10 percent when adjusting to altitude.
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