Overcoming Altitude

Most physiologists identify 3,000 meters (10, 000 feet) as being high altitude, though considerable effects on performance occur at elevations as low as 5,000 feet. Lake Tahoe sits at 6,200 feet above sea level.

As a physiologist and professional athlete, I am often asked the question “Does altitude training improve endurance performance?” The jury is still out on this question, and neither scientific studies nor individual experiences give definitive proof about the effectiveness of high altitude training.

High altitude effects physiology by decreasing the external pressure of oxygen. However, the relative concentration of oxygen remains the same at sea level and at high altitude, even on Mount Everest. When an athlete is exposed to high altitude, several adaptations allow us to compensate for the lower pressure of oxygen. The first and probably most important adaptation is that respiration rate increases. Increased respiration leads to dehydration. Another adaptation to altitude is a change in the blood, which allows oxygen to be delivered more easily to the working muscles to do aerobic work.

 These two adaptations occur in the 7-10 days of exposure to high altitude.

One of the long-term benefits of altitude exposure is an increase in the percentage of red blood cells in your blood. Red blood cells contain hemoglobin, which carry oxygen. More red blood cells helps improve your body's oxygen carrying capacity. It takes about 30-60 days for this to happen, so short-term won’t help. The downside of more red blood cells is an increase in the viscosity (or thickness) of the blood, which can put excessive strain on the heart – potentially causing life threatening conditions. Intense exercise is limited at high altitudes because of the decrease in pressure.

In fact, VO2 max – or your maximum aerobic capacity – decreases about 2.3% at 5,000 feet, and continues to decrease another 2.3% for every 1,000 feet. For someone living and training at 9,000 feet (such as Vail, CO) this decrease amounts to more than a 10% lower VO2 max value at high altitude versus sea level. As VO2 max is reduced, the ability to perform is reduced. Many athletes who live at high altitude and compete at sea level complain of a lack of foot speed in running, or power in cycling. It is easy to see how this happens, since they are unable to train at race pace because of altitude.

 For athletes who will be competing at high altitude, being acclimatized to that altitude is a benefit. Even residents in Boulder (5,400 feet) who travel to the Nissan Xterra Central Championship in Keystone, CO need to adapt to this higher altitude (9,000-11,600 feet). For the Nissan Xterra USA Championship in Lake Tahoe (6,200 feet), high altitude adaptation will be a benefit for those who are lucky enough to live at altitude. For most people, this is not possible, so some alternative strategies are suggested.

1. Your arrival can help improve your performance at altitude – even if you aren’t adapted. Optimally, you should arrive a week before the race. For most people, the third day at altitude tends to be the worst.
2. Nutritional Strategies:

• You need to stay hydrated. Since you will be losing significantly more fluid that you do at sea level, be sure to drink more than usual. Avoid alcohol and caffeine for the first few days at altitude, because both are diuretics that cause you to lose additional fluid. Also, most altitude environments are very dry. Sweat evaporates so quickly that athletes don't know they're sweating. Be extra careful to maintain fluid intake when competing at altitude.
• Eat more carbohydrates. Since your body is undergoing some stress at high altitudes, your body begins to burn more carbohydrates than usual. Since carbohydrate is the primary fuel that you use during high intensity training and racing, make sure that the tanks are full!
• Avoid acute mountain sickness (AMS) when exposed to altitude. Common complaints include headache, nausea, and lack of appetite. In most individuals, sleep is disturbed at high altitudes. To help alleviate symptoms of AMS, be sure to stay hydrated, get plenty of rest, and be sure to eat enough – even if you are not hungry. These strategies should help you perform your best – though don’t expect to beat your sea level times at altitude!

 Neal Henderson is a PowerBar sponsored XTERRA PRO, and is the Coordinator of Sport Science at the Boulder Center for Sports Medicine.