Altitude: Training and Racing
Just about everyone that we come into contact with speaks in a near mythical fashion about training at altitude and how athletes who do so have a huge advantage over those who do not. What does the science have to say and what can we do as athletes to increase our performance by including altitude?
As an athlete goes higher in elevation, the atmospheric pressure decreases, the air is less dense and there are fewer molecules of gas in that environment, leading to the partial pressure of the gasses oxygen (O2), nitrogen (N2) and carbon dioxide (CO2) to decrease. This has a direct impact on the saturation of hemoglobin, therefore O2 transport to working muscles. This lower partial pressure is referred to as hypoxia (sea level partial pressure is “normoxia”).
Long-Term Aerobic (with oxygen) Performance
Long-term or endurance events such as triathlon are without a doubt aerobic events, which are primarily dependent upon oxygen delivery to the working muscles. At high altitudes, hypoxia will have a direct impact on performance.
If we take a look at the performances at the 1964 Olympic games (Tokyo at sea level) and contrast them to the 1968 Olympic games (Mexico City at 2300 meters/7400 feet), we would expect to see a decrease in performance in 1968. Here are the results:
Maximal Aerobic Power at Altitude
The decrease we saw when looking at the winning times in 1964 v. 1968 is very similar to what we would see with detraining. If you look at the graph below, you’ll see the corresponding decrease in VO2max that accompanies an increase in altitude.
The decreases in VO2max is 12% at Mexico City, 20% at Leadville and 27% at Nunoa, which equates to roughly an 11% decrease for every 1000 meters above 1500 meters (3281 feet).
The main reason for this decrease in VO2max is NOT the decrease in cardiac output (Q), which is the product of heart rate (HR) and stroke volume, but instead the decreased saturation O2 of hemoglobin (the protein that carries O2 in your blood) due to the decrease in partial pressure. At sea level, hemoglobin is 96-98% saturated, where at 2,300 meters (1968 games), hemoglobin is only 71-88% saturated!
If you take a look at the ventilatory (breathing) response at altitude. It is clear to see the amount of oxygen uptake (VO2max) is corresponding to an increase in breathing rate (pulmonary ventilation). The end result is an increased heart rate and ventilation rate due to the lower oxygen content at altitude, which has the ability to lead to increased fatigue when compared the same intensity at sea level.
Adaptation to Altitude
So that being said, what happens when we spend time training at altitude? It increases the amount of red blood cells in the body to compensate for the decreased saturation of hemoglobin.
Training at Altitude
What happens when we ascend to altitude? Upon arrival, athletes will experience a decrease in VO2max (8-22% at 2,300 meters) due to the degree of saturation of hemoglobin. If an athlete stays for 10+ days, they will see their VO2max increase, some less than their VO2max at sea level, some back to their VO2max at sea level and some with an overall increase of VO2max!
The way around this, for serious athletes, is the “live high, train low” theory. That is, to train at a high altitude (around 2,300 meters) and train at a lower altitude (<1,400 meters). The main reason for this is the quality of high-intensity training. At altitude, it is far more difficult for an athlete to maintain the velocity and/or power output for a given interval.
The physiological impact of living at altitude leads to an increase in red blood cells and plasma erythropoietin (EPO), which leads to an increased VO2max!
Take Home Message
The take home message is, that if you live at altitude, you will see an increase in VO2max due to the increase in red blood cells and EPO. If you do not live at altitude and take a trip to altitude in order to train, it on average, takes at least 10 days to see any real changes in red blood cell count, EPO concentration and VO2max. Therefore, if you are going to a race at altitude and want to ensure you are as acclimated as possible, it is recommended to arrive at altitude at least 10-14 days ahead of the race, if not more.