The Side Effects of Exercise in High Altitudes

Couple mountain biking

The terrain and scenery at high altitudes can be incredibly beautiful and peaceful. It can also be tough on your body if you're not acclimated to it. The low levels of oxygen that high altitudes subject you to can make you feel tired, weak and can lead to severe altitude sickness in extreme cases. If you're venturing to the mountains for some exercise, it's important to understand the risks of altitude sickness and the things you can do to make your acclimatization as comfortable as possible.

Physiological Response to High Altitudes

There are several things that happen to your body when exercising at high elevations. Blood oxygen, blood plasma, blood volume and stroke volume are all reduced, while fluid loss, heart rate and metabolic rate increase. Your breathing rate increases as your body attempts to get adequate oxygen. Increased respiration then raises the acidity of your blood. Because your oxygen intake is decreased, your VO2 max -- the maximum amount of oxygen your body is capable of utilizing -- is decreased. All of these things combine to create a sensation of sluggishness and fatigue at high altitudes that you wouldn't experience at sea level.

Dangers of Altitude Sickness

Whenever possible, you should slowly increase altitude to avoid acute mountain sickness, or altitude sickness. Basic symptoms are common and include headache, nausea, dizziness, loss of appetite, shortness of breath and difficulty sleeping. Symptoms are often worse at night, but will usually begin to subside within 48 hours. Moderate altitude sickness symptoms include severe headache, vomiting and lack of coordination. Curing the symptoms of moderate altitude sickness requires descending to lower altitudes or medication. In severe cases, persistent coughing, bubbling sounds in the chest, convulsions and double vision can occur. Medical attention must be sought immediately if any severe symptoms become present.

Recommendations for High-Altitude Exercise

The IDEA Health & Fitness Association offers several suggestions for high-altitude exercise. At elevations over 3,000 feet, your VO2 max will decrease about 2.6 percent for every 1,000 feet. Because your VO2 max is reduced, you won't be able to exercise with the same intensity that you can maintain at sea level. Instead of performing long, endurance exercises, practice short, intense training sessions until your body adapts.

Other Tips

Nutrition and hydration are two other important considerations to make during high-altitude exercise. Your resting metabolic rate increases and your body experiences an elevated demand for carbohydrates at high elevations, so calorie consumption should be increased. Up your fluid consumption before and during exercise to combat rapid dehydration, which can be caused by the dry air and increased respiration. Be sure to wear sunscreen when exercising outside, since UV exposure is increased at higher altitudes. Your body produces more free radicals when you exercise at higher elevations, so taking a daily antioxidant is also a good idea.