Thursday, August 13, 2009

ATH: At Altitude

This is a bit after the fact, but interesting reading

Limiting Exposure At Altitude The Right Move

U.S. National Team Players Association

On Wednesday, we spoke with Dr. James Stray-Gundersen, one of the experts on altitude training for athletes. Dr. Stray-Gundersen has served as physician/physiologist for the US Cross-Country Ski Team and was a team physician for Norway’s Olympic Team in 2002. He is the co-author of “Live Hi/Train Low” now considered the defining study on altitude training for sea level performance. He was one of the experts attending and presenting at a FIFA symposium on altitude.

USSoccerPlayers: First, off, explain what effect altitude has on an athlete’s body without sufficient acclimation.

The pertinent difference at altitude compared to sea level is that the air is “thinner”, meaning that as one increases altitude in the atmosphere, the air pressure decreases. When air pressure decreases, the molecules in the air spread out such that a given volume of air contains fewer molecules of oxygen.

Our bodies rely on a certain amount of oxygen coming in to do things like sleep, study, run marathons, or play soccer. Interestingly, brief, single, athletic performances (less than 60 seconds like the long jump or the 400m run) are improved at altitude as we witnessed in the 1968 Olympic Games in Mexico City. That's because the air is less dense and easier to move through and the athletes do not require a sustained oxygen delivery for their event.

When we go to altitude where there are substantially fewer oxygen molecules in a given volume of gas (~2/3rds), we breathe harder, faster and deeper during rest and exercise, but we still can’t make up for the difference in oxygen delivery. As we breathe in more oxygen, we also exhale more carbon dioxide than at sea level. Greater loss of CO2 causes the acid balance in the body (pH) to increase.

One of our primary homeostatic mechanisms is to keep pH normal. To do this we start to secrete bicarbonate (HCO3-) into the urine. When we do that, we also need to send water (H2O) along with it. That water comes from our body stores. Also because we are moving more air in and out as we breathe harder, we are losing more water in each breath to the environment.

In addition, because our red cells are less than full of oxygen, a hormonal response occurs that concentrates the red cells by removing some of the liquid part of the blood (plasma), again leading to a dehydrated state.

This process starts immediately on exposure to altitude and the body continues to lose water for three to four days. It is substantially eliminated by breathing supplemental oxygen.

Athletes do not perform well when they are dehydrated and they fatigue quicker. Further, the days they are dehydrated take their toll in “wearing out” the player, so for each successive day at altitude the players become less capable of good physiologic/athletic performances.

Around the 3rd or 4th day, the body starts responding to these acclimatization changes and starts to come back towards normal.

By 10 days to two weeks, players are close (but not completely back) to sea level status. In studies on running performance, runners initially (~ day 5) ran 6% slower at an altitude of 5900 ft and steadily improved over 4 weeks to run only 3% slower (day 26) than they did at sea level.
In an attempt to keep blood pH normal, the body starts putting bicarbonate (HCO3-) in the urine and that causes a diuresis. In addition, the body loses plasma volume. Both these processes lead to a dehydrated and under-performing player.

USSoccerPlayers: What is the best way to acclimate an athlete to altitude?

The best preparation for performing in an altitude environment is living in an altitude environment. One could live in Aspen, Colorado or Park City, Utah or Flagstaff, Arizona, or one could live at “artificial altitude” by converting their bedroom or sleeping in a hypoxic tent. If those things are not an option, the next best thing is a 2-4 week camp at altitude prior to the match.

USSoccerPlayers: In a situation like the United States, where they only had a couple of days to train prior to Wednesday’s Qualifier against Mexico in Mexico City, what were their options?

The best option is to play before the physiologic processes of acclimatization have taken their toll. The idea is to avoid the process of acclimatization as much as possible.

That could mean flying in the morning of a late afternoon match or the evening before. One can further reduce the acclimatization response by supplying oxygen to the player once they are exposed to altitude. Essentially, then the players are not at altitude if they are supplied (during the days and hours before the match) with oxygen.

The worst preparation is to arrive a few days (3-5) prior to the match.

USSoccerPlayers: Why is that?

Because the players have been “worn out” by having to deal with the process of acclimatization and the associated dehydration, while they have yet not received the positive changes that will eventually come.

USSoccerPlayers: With only a couple of days to train, is there a benefit from doing that in a place like Miami where the highest point is less than forty feet above sea level?

Any place suitable to hold a camp would do.

USSoccerPlayers: Is smog a separate issue in preparation?

Yes, but one can’t “acclimatize” to smog. Exposure ahead of time just inflames airways and makes it hard on the players. The best approach is to spend time before the game in an environment with clean air.

USSoccerPlayers: Following the game, players are released back to their clubs and make the return trip to Europe or teams in Major League Soccer for games over the weekend. What is the recovery time after playing in a place like Mexico City?

Recovery from strenuous, stressful exercise at altitude takes longer than at sea level. Recovery from jet lag is another consideration, but if the total time away from Europe has been minimized and brief (around three days), the players can avoid most of this. The air pollution and the stress of an important competition also take their toll and the players must use some of their energy reserves to come back and play well for their club teams.

USSoccerPlayers: Major League Soccer has teams and stadiums in Sandy, UT and Commerce City, CO. Does playing at altitude as part of a regular schedule or being based at a club at altitude increase a player’s ability to cope with extreme altitudes like Mexico City?

Playing a game or two in Sandy, UT (4,450 ft) and Commerce City, CO (5,164 ft) are generally insufficient exposure to altitude to have much of an effect on a subsequent match in Mexico City (~7,500 ft), although they will know how the ball behaves at altitude. There would be an advantage for players on the Real Salt Lake and Rapids squads in coping with altitude conditions.

I would like to add that football (soccer) is a complicated, exciting game that is, in part, a function of fitness and physiologic capabilities, but also very much dependent on the players’ (and coaches) brain functioning optimally.

Acute exposure to hypoxia or altitude impairs many aspects of brain function... cognitive function, memory, what the player thinks they may be capable of and overall feelings of well being. These are additional considerations in the approach to altitude competition.

Again these issues are minimized by longer term residence at altitude or by avoiding altitude as much as possible by arriving shortly before the match and by the use of supplemental oxygen.

In summary, there are additional stressors faced when sea level players are playing at altitude. They can be minimized either by living at altitude for a substantial period of time or by avoiding altitude by coming up close to the time of the match and using supplemental oxygen to blunt the changes occurring from acclimatization. Logistics of busy professional players usually make the latter the course of action.

For the 2010 World Cup where the US may have a series of matches at these altitudes (Johannesburg is at 5,751 ft), taking the time to acclimatize would give the United States an advantage.

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1 Comments:

At 12:11 AM, Anonymous Anonymous said...

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