By Eric Heiden, M.D.
Training and racing at altitude can be better handled if certain dietary concerns are addressed. This article will focus on the requirements for athletes exposed to altitudes between 1500 and 3500 meters, what most would consider moderate altitude. These moderately high altitudes are probably much more frequently encountered by athletes in the U.S. and Europe.
The three main nutritional areas of focus for athletes at altitude are: optimal hydration, caloric requirements, and antioxidant balance.
Hydration – Exposure to altitude increases loss of water through increased respiration . This occurs because at altitude ventilation increases in response to the hypobaric environment, which also results in increased heart rate, even at rest . Although the percentage of oxygen remains the same at higher altitudes, the atmospheric pressure decreases, and the result is that for a given volume of air there are less total oxygen molecules present. Since body water is expired with each breath and the rate of breathing increases at altitude, more fluid intake is needed to maintain fluid balance during altitude exposure. With the heart rate already increased, even a slight drop in hydration can begin to affect riders since the HR would need to increase even further to pump oxygenating blood. Another factor that may impact fluid balance during exposure to altitude is increased urination [3,4]. Because of the wide range of altitude, temperature, exercise duration, intensity and athlete mass it is difficult to provide specific recommendations for fluid replacement while at altitude. However, weighing yourself pre, and post exercise will give you guidance for your fluid replacement needs. The volume of fluid consumed should be greater than the volume of sweat lost to provide for the ongoing urine losses . Fluids should contain water, electrolytes and at altitude carbohydrates may be advised .
Caloric Requirements – High altitude exposure can result in increased RMR (resting metabolic rate) and as discussed above results in increased heart rate [7,8). Also, high altitude exposure can cause a decrease in appetite [9,10]. This combination can lead to unwanted loss of body mass and/or an athlete who isn’t properly fueled for upcoming training sessions or races. Another factor that could influence caloric replenishment protocols is the shift towards carbohydrate metabolism that occurs at altitude . At altitude, the respiratory exchange ratio increases (meaning more carbohydrates are burned) at a given exercise intensity compared to sea level and is elevated even during recovery. So, efforts to maintain energy balance can also impact hydration status at altitude. For this reason and because of potential decrease in appetite that can occur at altitude it may be prudent to include a higher percentage of carbohydrates in pre, post and peri workout fluids than normal as calories in fluids are more easily consumed than those in solids. Pay attention to your normal caloric intake at sea level and make sure to maintain that level at altitude.
Oxidative Stress – Oxidative stress and the role of antioxidants are a hot topic today in exercise nutrition. The reason for this is that the proper amount of oxidative stress appears to be necessary for optimal adaptations to exercise. As a result, consumption of antioxidants falls into the “more isn’t always better” category. Oxidative stress can be increased at altitude which can upset the balance between it and antioxidants [12,13]. This can lead to increased levels of inflammation and slow recovery. So, increased consumption of antioxidants may be warranted at altitude. To insure adequate amounts of antioxidants, athletes at altitude should consume a variety of berries, grapes and vegetables. If these sources aren’t available to the athlete, supplementation may be advised.
In summary, the nutritional guidelines for training and racing at altitude aren’t radically different from those at sea level. In short;
- hydrate properly: Include an adequate dose of electrolytes along with fluids to assure optimal hydration
- Calories: Consume drinks at a 6-8% solution to assure adequate calories along with proper hydration during exercise and maintain a healthy diet during down times at altitude.
- Antioxidant support: Consume a variety of fruits and vegetables to ensure proper antioxidants levels.
The difference at altitude is that deficiencies in any of these areas can more quickly lead to problems for the athlete than they might at sea level so high altitude can be a less forgiving environment of nutritional mistakes. Even a slight drop in glycogen or hydration can cause poor recovery and a sleepless night. Additionally, the potential for a decrease in appetite at altitude can compound these issues. In conclusion, prepare appropriately for high altitude training camps and races by bringing extra fluids, carbohydrates, and antioxidant rich foods. Also, make sure you have a reliable scale to keep track of your body weight during your stay at altitude.
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