Altitude in football: When to arrive
In the last few posts, I've been looking at the impact of altitude on football. It's an impact that extends beyond the simple "less oxygen" argument, because there are effects on the flight of the ball. However, we've looked primarily at how the player's physiology may be affected, and how this might impact on their performance.
The logical question that arises out of this discussion is "when should teams plan to arrive at altitude in order to minimize the possible negative effects?". And it is this question that is the focus of today's first post.
Two models: The Smash and Grab vs Patience pays
There is not too much research on this question. That may be surprising, but remember that for most professional athletes, across all sports, the issue of when to arrive at altitude is one that they rarely even contemplate. In Europe, sport is rarely played at even these moderate altitudes. In the USA, it happens so infrequently as to be an inefficient way to investigate physiology. And for individual endurance athletes, like cyclists and runners, altitude training is part of the package, with a majority now spending time at some altitude before racing, even at sea-level.
However, a couple of approaches have emerged, most of them from Super Rugby (a competition involving professional teams from New Zealand, Australia and South Africa), and from the Tri-Nations, an international competition between SA, Australia and New Zealand. In these tournaments, the Australian and New Zealand teams will travel to South Africa and spend either two or three weeks here, during which time they would play one or two matches at altitude (1,500m or higher).
So they consider this question all the time - do they stay at sea-level and travel up only for matches? Or do they base themselves at altitude and go down? This is the same question faced by World Cup teams in 2010.
What has emerged are two models, which I've called:
- The Smash and Grab
- The Patience pays
- In the "Smash and Grab", teams believe that there are two optimal windows for performance, and that if you play very soon after arriving, or much later, you'll achieve best performance. In this approach, performances will get worse before they get better, so you are better off arriving very late and thus playing almost immediately, or you arrive very early and allow for adaptation. This is what most of the New Zealand and Australian teams do - the idea is "get in, play, get out, and the altitude won't affect us too badly."
- In the patience pays theory, teams will perform worst on arrival, and then improve. In contrast to the late arrival, smash and grab theory, your performance doesn't get worse before it gets better. It starts badly, and then improves steadily. Therefore, your best chance is to get in as early as possible and play only after allow full adaptation. This, incidentally, is what most of the 2010 World Cup teams have chosen to do.
So, let's have a look at some evidence to see which of the above models has scientific support. Remember, what we're looking for is whether performance gets worse before it gets better (which confirms the "smash and grab" theory on the left, as opposed to a finding that you get better and better (confirming the model on the right).
Scientific studies: Physiology can't be tricked
First up, a study by Lundby in 2007. In this study, elite cyclists were taken up to 2,340m and tested weekly for three weeks. This is a big jump in altitude, so expect big impacts on their performance. But the principle is the same - we're looking for timing of performance impairments.
Below is a diagram showing the results of this study. In the top panel, you are looking at the peak power output achieved by the cyclists at 7-day intervals. The performance at sea-level is converted to 100%, and then each altitude performance is shown compared to that sea-level performance.
The bottom panel shows how time-to-exhaustion is affected. Again, the time from the sea-level trial is 100%, and the drop relative to this is shown by each bar.
The size of these drop-offs is probably larger than what you would expect in football, because of the nature of the game (intermittent vs sustained), and because 2,340m is a big change. At 1,600m, you'd be looking at smaller effects, but nonetheless, the finding is that you don't get better before you get worse.
However, what you're no doubt thinking now is that one week intervals is not enough to rule out that perhaps your best performances happen after say 12 hours, or even two days. Lundby might have measured performance during the worst phases. So we need a study with better "resolution"
For that, we look at a study by Weston (2007). Here, she took a group of rugby players from sea-level to 1,600m (Johannesburg, actually) and did a number of tests on them over the course of two days. Testing was done after 6 hours, 18 hours and 47 hours.
Below is a graph showing how shuttle run (the "bleep" test) performance was affected. Once again, sea-level performance is 100%, and altitude performances show the drop-off compared to sea-level.
So once again, you can see that performance only gets better. Worst performances happen 6 hours after arrival, and then slowly improve from that point onwards.
The combination of these studies thus suggests that the early arrival model is the best for performance, because there is no dip before the performance starts to improve. So when teams play in South Africa and stay at sea-level and fly up the day before a match, they play 24 hours after arriving (at least, sometimes more). It would seem that at this moment, performance is worse than it would be after 72 hours, and certainly after one week.
Therefore, the approach used by rugby teams to South Africa (New Zealand and Australia, and the British & Irish Lions last year) is without any scientific merit, at least as far as altitude is concerned. I have no idea where this theory originates, but I don't know of evidence that supports it. Two studies refute it outright, showing that the more time you have at altitude, the better your physiological performance capacity.
Note that this does not necessarily translate directly to football. I was at pains last week to emphasize that you can't simply apply endurance research to football, because of the nature of football (see last week's posts on physiological profile). The impact is likely much lower in football.
However, the principle remains - physiological capacity is lowest on arrival. And it is for this reason that most of the teams in the FIFA 2010 World Cup have chosen to base themselves in the altitude centres of South Africa. France are the one big name team to choose sea-level (though we've seen how France's tournament has gone - this is not the fault of altitude, I must point out!). All the others are in Johannesburg, Rustenburg, Pretoria, Potchefstroom, and that's because they recognize what the science seems to show - the longer, the better. Patience pays.
It's not just altitude: the holistic view
One final point is that one can become a little pre-occupied with altitude. And I must point out that there are other factors that impact as much on performance. A team's state of mind is incredibly important, and in a four-week tournament, plus two weeks build-up, to be based in a sub-par facility at altitude is probably worse than being in a world-class facility at sea-level!
So the point is, we've spoken about selection of an altitude base as being important, but this does not factor in that the team and its players may choose to be at sea-level simply because the facilities, the environment, the extra-curricular activities and the general experience is much better there. In that case, a 5% negative effect might be offset by a benefit. Traveling to altitude late can thus be justified if it is understood that one is doing so for reasons other than physiology!
But, if a team says they're staying at sea-level and traveling up the day before to "avoid the impact of altitude', well, they're in disagreement with what the research shows!
P.S. I was fortunate enough to attend two matches over the past weekend - Cameroon v Denmark at Loftus and Brazil v Ivory Coast at Soccer City on Sunday. Both were fantastic experiences, vuvuzelas and all. Some thoughts on that will come in a short post later on!