Football players are among some of the best conditioned athletes in the world. During a match in the EPL, a player will regularly run around 10 kilometers while making runs that will shoot his heart rate and fatigue way up.
Study after study shows that recovery rate is one of the best predictors of performance and that the elite players do it best. With the conditioning and sports science staffs at most of the top clubs constantly working on this issue, it's no surprise.
Yet there's one factor that is beyond anyone's control that can fell even the mightiest of players. Watching the U.S.-Mexico match slow down until the frantic ending gives us an idea of just how fatigued some of the players were, but there was no more clear sign of how tough it is to play at altitude than when Lionel Messi, the world's best player, was left heaving up fluids.
(Then again, Messi has done this before and at much lower altitude, as this video from last week's game against Venezuela shows.)
At nearly 12,000 feet above sea level, the Estadio Hernando Siles is one of the highest stadiums in the world, more than double the altitude of Denver's famous Mile High Stadium, where players in the NFL often struggle.
With just a few days to get ready, the normal acclimatization simply is impossible, leaving national teams to struggle with getting their teams together as well as trying to fight off the effects of altitude.
Altitude causes problems for players due to changes in oxygen at that altitude, but contrary to popular belief, it is not because there is less oxygen. Atmospheric oxygen stays stable at about a 21 percent mix up to nearly 70,000 feet.
Instead, it is the air density that reduces, which also reduces the saturation of oxygen and the arterial pressure inside the body. At what is called "very high altitude" by Dr. Paul Auerbech, the oxygen saturation in the body can get below 90 percent, causing problems during activity and sleep, often leading to true altitude sickness.
This "very high altitude" is from 11,500 feet to 18,000, or exactly where Hernando Siles is placed.
The symptoms are rather universal: headache, nausea and fatigue. For people that quickly go to altitude and have not gotten used to the air over a period of time, either naturally or assisted, these symptoms are common. It can get worse, even deadly, but well-conditioned athletes seldom show even the slightest signs of further damage, such as High Altitude Edema, which can be deadly.
Over a relatively short period of time, most healthy adults can adjust to the change in oxygen availability. Athletes don't often have this amount of time and are forced to use other methods. Runners and other endurance athletes will often use altitude to their advantage, training there for a time to force their bodies to adjust and then returning to a lower altitude for competition.
One of the most popular is the use of a hypobaric chamber, which simulates the altitude by removing oxygen from inside a closed environment, such as a room or more commonly, a tent.
Hypobaric treatment is often confused with the more popular hyperbaric treatments, but by definition, it is the reduction in pressure and oxygen availability (hypo- means "reduced below normal") that helps an athlete adjust to altitude conditions.
There are also devices that look like masks that make it more difficult for an athlete to breathe, reducing the oxygen and simulating the conditions. The efficacy of these is in question and wearing one is often uncomfortable.
For a time, these kinds of treatments were considered an unfair advantage and were banned by WADA, but since 2006, both hypobaric and hyperbaric treatments have been considered clear.
Of course, there are techniques and substances that can help with altitude sickness that are banned. The commonly used medication Diamox is a banned substance under WADA guidelines despite its wide use, due in large part to its diuretic properties.
Other substances that can increase oxygen transport range from EPO and CERA, the red blood cell activator widely used by cyclists, to simple blood doping. This procedure, where blood is taken from a person and then re-introduced a few days later after the body has replenished itself, is seeing a surge in popularity after EPO became detectable.
Once on the field, there is not much that can be done for athletes. Oxygen supplementation is widely used and can have some mild and short-term effect, but it does not help the body adjust to the actual conditions.
Players who are playing one big game at altitude usually don't care about the adjustment and just want to feel better now. Seeing the cans of oxygen littering the sidelines at games in places like Bolivia and Peru, or even in Colorado, is not uncommon or ineffective.
The last question then is why teams would schedule these games? For a smaller country like Bolivia, they'll take any advantage they can get when playing a powerhouse like Argentina or Brazil. If having players that are acclimatized gives them the advantage over players that are not, so be it.
Lionel Messi normally plays at an altitude of 35 feet above sea level, so it's no surprise that shooting across the Atlantic and up the Andes would take something out of even a player like him. Contrast that to Di Maria, another Argentinian star who plays in Spain.
However, Di Maria plays for Real Madrid, who's home city is at 2,000 feet. Di Maria's normal long winding runs up the line might show that he was a bit more acclimatized, though he too was left gasping for oxygen at times.
Even Sergio Aguero was left struggling, putting out this tweet:
A tie up on that altitude is worth a win. What a brilliant effort from the team! C'mon, Argentina!
— Sergio Aguero (@aguerosergiokun) March 26, 2013
Home field advantage is more than just passionate fans, but sports science and medical staffs around the world struggle with preparing their players for games played at altitudes like what we saw in the Argentina vs. Bolivia matchup. There is no easy solution and we are likely to see more heaving stars the next time the game is played at such great heights.