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Wednesday, June 16, 2010

Football 2010: Impact of altitude

Altitude and the 2010 World Cup

In our last few posts, we've looked at the physiology of football, the activity demands of a match, and also the fatigue component, which is vitally important, particularly in the final 15 minutes of matches. Incidentally, almost one-third of goals are scored in those final 15 minutes.  This is a function of many things (mental and strategic factors being among them - the impending whistle drives teams into action), but fatigue may be crucially important here too.

The stage has thus been set to discuss altitude and its effects on football performance.  In fact, it's the perfect time, because I was just reading in a local paper that both Denmark and the Netherlands have blamed the altitude on their lackluster performances in Johannesburg on Monday.  So clearly, a good topic to discuss!

Over the last three years, we've built up a readership that is primarily endurance-based (if you're new to us thanks to football, welcome!), and so most of you will appreciate the impact that altitude has on distance running or cycling.  It's obvious to you if you have ever traveled from sea-level to anything above 1,000m and tried to run 5km or 10km.  (If not, run Bolder-Boulder 10km and you'll find out in your experiment of one!)

Not quite as clear is the impact of altitude on football.  And this is why those posts on physiology were vital - they painted a picture of the physiology, and we saw how the key aspect for footballers is the ability to repeat sprints, lasting only seconds, but with short recoveries.  Let's now consider the impact of altitude on that performance.

South Africa - a unique elite sports challenge

First, South Africa is unique in that no other country I can think of demands that elite sportspeople perform at sea-level and then at altitude with such regularity and with such short turnaround times.  There are of course plenty of altitude venues, but few that I can think of are utilized as frequently and for the stature of event hosted here.  We host European PGA golf events where the transition happens three days later.  International rugby is played at sea-level with another match at 1,700m only a week later.  International cricket matches.  And now football.

Recently, there was much consternation because an ATP Tennis Masters Series event was played at the "altitude" of Madrid only a week before the French Open - players felt the altitude would hamper recovery.  Madrid is at 650m.  Johannesburg is double that, plus 400m.  Four weeks of high intensity play, plus training, adds up to a physiological challenge that 'scared' a lot of teams (and FIFA) ahead of this World Cup (more on that later).

In all these sports, altitude affects performance in various ways.  Broadly, there are two effects - one is on the physiology, which is the focus of this post.  The second is on the flight of the ball - reduced air density means faster, further and higher, as any golfer will tell you!  So let's consider the physiology, always drawing on what we already know of the activity demands of the game.

Impact of altitude on repeat sprints

For the clearest illustration of the effect of altitude on exercise, go back to 1968, and the Mexico City Olympic Games.  Remember Ron Clarke, a dominant runner heavily favoured to win gold at 10,000m, lying collapsed on the track after the race.  To this day, he blames the altitude for heart problems he experiences.  Mexico City's altitude of 2,200m imposed a significant challenge for distance runners, and it's no co-incidence that a) the times in those events were uncharacteristically slow in 1968, and b) all the middle- and long-distance events were won by African runners.  Those Africans, who all live and train at altitude, used the 1968 Mexico Olympics to announce themselves to the world as a distance running force.

At the other extreme, sprinters benefit from altitude.  Bob Beamon nearly jumped over the sand pit, setting a long-jump world record that would not be challenged for 27 years.  100m, 200m and 400m sprint times were faster than ever.  The reduced air density, punishment for distance athletes, was pleasure for sprinters.  It is this factor that may be affecting at least part of the ball-flight in the 2010 WC, but that's for a future post on altitude in football.

For football, the problem is that sprints are repeated over and over, with short recoveries.  It's therefore a hybrid of the two extremes, and we have to jump straight in and find studies that have replicated repeated sprints to find out the impact of altitude.

Below is a graph redrawn from a study by Brosnan et al (2000).  Elite cyclists were asked to repeat six 15 seconds sprints at an altitude of either 585 m or 2,100m.  This was done three times: Once with a rest period of 45 seconds (a 1:3 work-rest ratio), another time with 30 seconds rest (1:2) and finally with 15 seconds recovery (1:1).  The sea-level performance is shown in blue, altitude in red.

Quite clearly, there was an impact, which I would summarize as:
  • Altitude reduces sprint performance by between 5% and 10%, depending on the rest period
  • When rest is larger (the 1:3 trial, with 45 second rest), performance is 5% worse
  • Shorter rest amplifies the altitude effect, and performance is 10% slower
  • Very importantly, performance is reduced from the first sprint (circled in green).  The body is not so 'stupid' as to exercise blindly until the altitude 'catches up with it'.  Rather, there is anticipation and pacing, so that from the very first sprint, the cyclists produce 5% less power output in response to less oxygen. 

    The concept of a pacing strategy for football is not one that has been discussed or thought about a great deal.  It's difficult to measure, for one thing.  But I believe that the biggest impact made by acclimitazation is the improved ability to pace oneself. And the corollary is that teams not adapted will be compromised by this impaired ability to regulate effort over 90 minutes.
This finding was replicated in a study by Feriche et al (2007), where 400m sprints were performed.  When rest periods were between 1 and 2 minutes long, the 400m times were 10% slower at altitude than sea level.  However, if rest periods were increased to 5 minutes, then the difference in performance disappeared.

The point now is that work:rest ratio has a crucial impact on performance.  This is why I emphasized it in the previous posts - if the rest increases, the negative effect of altitude is negated.  So, in the World Cup, if teams play at a high intensity, with more off-the-ball movement, and more ball movement to force opposition into reduced rest periods, then the altitude is far more in play than if the tempo is reduced.  So far, I've been surprised at the relative lack of tempo, but that might be the effect the altitude is having on BOTH teams (though of course this is no excuse for France, Portugal, Ivory Coast, who have played at the coast). 

FIFA's approach:  What altitude?

These studies, plus my own experience of football, hockey and running convince me very strongly that  the altitudes of South Africa's inland venues have a significant effect on performance.  I learned this the hard way, when I first tried to compete at altitude after moving to Cape Town from Johannesburg for my studies.  I was minutes slower over 10km, and played football and hockey feeling like I'd developed asthma, emphysema and sinusitis all at once.  The studies suggest the same - the graph below, for example, shows how VO2max (a measure of exercise capacity) and time to exhaustion at high intensity are affected by altitude.

Quite obviously, there is an effect as soon as you head up from sea-level.  In fact, the impairment in maximal exercise (shown on the left) is 6% per 1,000m and sustained exercise is affected even larger (right side).  So it doesn't happen only at 2,000m.  Similarly, the studies I've just looked at above show a 5% to 10% impairment in performance when the altitude difference is 'only' 1500m'.

So imagine my surprise when a FIFA consensus statement appeared in the Scandinavian Journal of Medicine and Science in Sports in 2008.  In it, moderate altitude was defined as anything above 2000m.  Anything between 500m and 2000m was termed "low altitude".  And at low altitudes, it was said, "minor impairment of aerobic performance becomes detectable" (emphasis mine).

I have subsequently received an email from one of the scientists involved in crafting that statement, and he has explained that the categorizations were derived from three factors - the effect of the altitude on performance, the risk of altitude sickness, and the importance of and length of time required for adaptation to the altitude.  By these criteria, certainly, altitude sickness is hardly a risk in Johannesburg, and so it qualifies as "low altitude".  One would question whether this is relevant for football in South Africa, however.  He has also said that FIFA had little to do with the content and gave no direction to the panel.  I trust that this was the case. 

However, at the same time as this was happening, FIFA were clamping down on any talk about altitude in South Africa.  Scientists here (including yours truly) were told in no uncertain terms to refrain from speaking about it.  I spent two years working in sports business and that brought me into contact with the "unwritten rule", which as near as I can tell was created so that all cities in SA had equal chances of hosting teams during the tournament.  In fact, some of the work I did in the lead-up to the tournament was to consult to teams on our recommendations of base camps based on all factors, including altitude.

It was quite clear that altitude was to be scrapped off the list of factors, at least from the FIFA side.  We could extol the virtues of the candidate host city - its nightlife, its golf courses, its climate, its hotel facilities, its welcoming people.  But altitude - that was irrelevant. The economic "punishment" imposed on the sea-level hopeful hosts would not be allowed.  For this reason, the consensus statement supported the notion, because FIFA could then point to it and say "All matches in SA are at low altitude, which means minimal impact on performance, and minimal time required for adaptation.  Therefore, no potential host city/base camp is at a disadvantage with respect to its elevation".

And while I appreciate the other categories for the definition (particularly the likelihood of developing altitude sickness), the issue for elite footballers in the 2010 WC was not altitude sickness, it's the 1% difference in performance, and the negation of this through sufficiently early arrival.  As for not needing adaptation - the Dutch and Danes have had some adaptation.  Their comments suggest they'd have enjoyed more time to adapt!

The point of all this is that the altitude was downplayed - you didn't see it in the media, you didn't hear much about it.  By design.

Why altitude matters, despite the "minor impairment" of "low altitude" 1,700m venues

I must make three points here.  First, at the elite level, a 1% impairment in performance is significant.  And we know (as shown above) that endurance performance falls off by 14% per 1,000m altitude gain.  We know that a 1,500m difference produced a 7% impairment in repeat sprint performances.  That's not "minor" - it's massive.  But even if it were minor, it would be relevant to teams hoping to win a World Cup.

Second, no one would dare suggest that "high-altitude" training centers are in fact at low-altitude, and perhaps should not be bothered with.  I had the pleasure of being hosted by Prof Randy Wilber and my friend Bobby McGee in Colorado last year (altitude between 1,500m and 2,500m), where hundreds of athletes train, and millions of dollars have been spent on facilities at altitudes which are implied to impose little or no physiological or performance strain .  There is clearly something wrong with that picture, and so while there has been a lot of debate about the impact of altitude, I think the unequivocal answer is that altitude affects performance, even in Johannesburg.

Finally, I don't even think it matters in the larger picture, and I don't understand FIFA's desire to keep the issue away from the headlines.  The altitude will affect performance, but it won't be decisive.  If anything, it adds an interesting angle to the tournament.  Just as golfers, tennis players, marathon runners, cyclists must adapt to environment and geography, I see nothing wrong with altitude as a factor.

Altitude and the game - how does it change?

The short answer is that no one really knows, because it's never been studied.  However, these are the obvious changes I would hypothesize you'll see in a match (assuming you were able to measure it):
  • Players should cover less distance at altitude than at sea-level. We saw that players run anything between 10 and 15km in a match.  Altitude would reduce this.  By how much, we don't know. 5%? 10%?
  • The sprint distances will be reduced - remember how I posted about how a key difference between good and great players is that the great players sprint more and do more high-intensity running than the good players?  Well, there's a sense in which altitude will turn the great players into good players, at least in terms of their sprinting and running distance
  • The drop off in the second part of the match will be even more pronounced.  This is because even though pacing strategy is altered at the outset, the dynamics of the game force players into a strategy and so there will be a 'payback' at the end.  The fatigue related decline in sprint performance, which I looked at yesterday, will be more pronounced at altitude
  • Players will attempt fewer sprints in a match.  This is because they do not recover adequately, and will look at ways to increase the rest period (to decrease the work:rest ratio, in effect).  This means passing up opportunities to sprint
  • Decision-making will be compromised, as will skill execution as a result of fatigue and other sensations (breathlessness, for example)
  • Generally, the tempo of the match will drop as both teams attempt to conserve energy and delay fatigue
So what to do - acclimatization is key

The solution to prevent this is to allow maximal physiological adaptation.  As I've repeated, even a 1% impairment could be costly - we've seen in this World Cup that matches will be incredibly tight, and so every margin matters, however tiny.  And I cannot, in a high performance environment, see any option other than allowing full adaptation.  The German team doctor spoke on local television the other day, and he echoed these thoughts.  Basically, if a team is spending fifteen hours a week training, and if they are spending another 10 hours a week looking at video to analyse opposition to find an edge or weakness, taking supplements, stretching, massaging, doing everything they can, then they cannot simply set aside a factor that can affect them by even 1%, let alone 7%.

At this stage, I must also point out that there are other crucial components to pre-match preparation, which may even offset an altitude disadvantage.  For example, if a team feels that the base facilities, environment, support staff and extra-curricular activities are far superior at the coast, then they may well make an informed decision to base themselves at sea-level, and take the altitude knock.

However, to disregard it would be reckless at best.  It will thus come as no surprise to you to learn that all but a handful of the 2010 teams have chosen to go up to the altitudes to base themselves.  They may miss out on the sea and mountains, but they control the physiology!

There is much more to be said - for one thing, the timing of arrival is the crucial question.  If you are playing at altitude, when should you arrive?  But, this has already been a lengthy discussion, and I know you must be saturated with soccer right now.  So let's put that aside for next time!

Looking forward to the matches - batch 2 of Round 1 commences, hopefully with more inventiveness

On the field, the tournament is struggling to hit any great heights in terms of attacking play and inventiveness.  I've been very disappointed at the apparently negative mindsets of teams so far.  And while I can appreciate the gravity of the first match of the tournament, I do hope that the second batch of matches produces some more attacking football.  There is a stat, for example, that only 13% of the teams who lose their first match will qualify for the second round.  50% who draw will qualify, and 86% of teams who win go through.  By the time you reach the second match, those teams who have drawn game 1 find themselves in a far more precarious position and may be compelled to be more adventurous.  Those who lose are in a must-win, and so in theory, games should open up.

There is risk and reward, and my impression has been that risk has outweighed reward, leading to a generally dour spectacle and teams who sit back.  A simple exercise of counting numbers when teams attack will show that few are committing numbers forward.  Under those circumstances, errors allow goals, as we've seen.  And errors don't happen too frequently at this level.  Some of the finishing has also been particularly poor.  Some have blamed the ball, some the pitch, some the vuvuzela.  I don't have an answer, I just hope that the creativity improves.

And I don't necessarily want to see 5-3 victories or 7 goal thrillers, but even chances have been in short supply.  So far, 14 matches have produced 23 goals, 1.6 per match.  We're only 20% of the way through the tournament, but the average in previous World Cups is 2.4 goals per match.  So we're well down - 11 goals down, in fact, according to averages.

Also, six of the 14 matches have been drawn, and 11 of 28 teams have failed to score.  In the second batch, because the stakes, teams will have to be more attacking - another draw becomes very costly, and so I expect we'll see more inventiveness.

That second round of group matches starts tonight, when South Africa meets Uruguay in Pretoria.  The expectation is once again massive, and the optimism even greater after SA's start against Mexico.  Let's hope it is the catalyst for the tournament to erupt.  Before that, a tournament favourite Spain takes on Switzerland, and Honduras play Chile in the first match today.

All eyes on Loftus tonight though, to see how the hosts go.  As usual, we'll do our best to follow on Twitter for those without access to TV!



Alan Ruddock said...

Dear Ross and Jonathan,

Great series on the physiology of football. Not only does the altitude affect the physiology of players but also the referee's. It would be interesting to observe the interaction between fatigue caused by altitude and the decision making performance of referee's. Here at the Centre for Sport and Exercise Science, Sheffield Hallam University, UK we prepared referee English referee Howard Webb for the world cup by conducting a mix of intermittent hypoxic treatment at a simulated altitude of 2000 - 3000m and high intensity interval training at 1500 - 2000m. The training period lasted 4 weeks (12 sessions) and was conducted prior to a 7 day acclimatisation camp in Pretoria. Please find a link to the BBC sport World Cup website highlighting the work we have done with Howard.


Also please find a link to an article and video detailing the possible effects of altitude during the world cup featuring Professor Steve Haake on the new scientist website.


Really enjoying this series, keep up the good work!

Alan Ruddock
Centre for Sport and Exercise Science, Sheffield Hallam University

Mark said...

The lack of attacking play, the paucity of goals and the defensive mindset of the teams may be disappointing, but they are certainly not surprising. The effects of altitude, the new lighter ball and the vuvuzelas are all contributory factors. My contention (as per my post under the vuvuzela topic) is that the players, being the best in the world, can and will adapt to the altitude and the characteristics of the ball. Sportsmen and women in other sports do it all the time. What they will find a lot harder to adapt to and will prevent them from playing to the maximum of their abilities is the fact that they are effectively hearing impaired. The vuvuzelas are not only detracting from the viewing experience, they are hampering the players in a way that I am surprised is not being discussed in more detail as I am sure there must be studies that have looked at the effect of hearing loss on sporting performance.

Not only can’t they hear their coach or their team mates, meaning that they are effectively playing in a vacuum, but more importantly, their inability to hear the ball strike of their team mates and opponents mean that they are deprived of the vital cues they need to determine the speed and flight of the ball. This is not something that they will adapt to easily, if at all. Those who are hearing impaired are more attuned to extra visual cues to make up for what they cannot hear. The soccer players are not going to reach this level of visual awareness, and even if they did, the lack of hearing still means that their performance will be sub-maximal because there are certain things that the eye just can’t tell you but the ears can.

As I said in my vuvuzela post, this does not necessarily mean that we won’t see good contests or exciting soccer. But it does mean that we won’t be seeing soccer skills at their best and it does mean that the less skilful teams and those lower on the soccer rankings (such as the hosts) will be advantaged because handicapping such as this tends to level the playing fields. Not unexpected then that the host captain in his last interview expressed his wish for the noise of the vuvuzelas to continue.

Ross Tucker and Jonathan Dugas said...

Hi Alan

THis is great, thank you so much for the information. It's definitely going to be the subject of post, thanks to you.

Your research sounds tremendous and I'm looking forward to going through it. If you have any other contributions, please don't refrain, I love to hear this kind of thing.

Right now, have to dash off - I'm heading to Johannesburg (altitude!) to watch a couple of games on the weekend. I'll be back later!


Ross Tucker and Jonathan Dugas said...

Hi Mark

I think you have a point, yes. The reason I haven't discussed it is that I don't know of any studies that have looked at the impacts. I'll try to find these studies, but I haven't found them so far.

I think it's certainly possible that the absence of sensory feedback impairs skill levels. It's definitely impairing communication on the field, as we've heard many people say.

I will say that I've experienced Twickenham rugby stadium with "only" 40,000 fans screaming and we couldn't hear each other then. No vuvuzelas, just human voice and it was still impossible to communicate over 20 m. I can only imagine what 80,000 COULD be like.

So I think the communication issue is one that these players will minimize. Your point about motor control is well taken. I'll follow up on it and see if anything interesting comes up.


Anonymous said...

"First, South Africa is unique in that no other country I can think of demands that elite sportspeople perform at sea-level and then at altitude with such regularity and with such short turnaround times. "

"I had the pleasure of being hosted by Prof Randy Wilber and my friend Bobby McGee in Colorado last year (altitude between 1,500m and 2,500m)..."

Denver (at ~1,600m) has all four major American professional sports. Say what you will about American football and baseball ( and I have), but hockey and basketball are fairly aerobic sports where players compete in Denver and at sea level within a few days.

I grew up in Canada (~75m) and moved to Boulder, CO. My first hockey game, it felt like someone had shrunk my lungs. I could barely skate from one end of the rink to the other without a rest. Last year's Bolder Boulder was nothing to write home about either.

Other than my minor quibble, I did enjoy the post (as I do with all of them). Thanks, and keep up the good work.

Ross Tucker and Jonathan Dugas said...

Hi Anonymous

Thanks for the post. and for reading and supporting the posts!

You're quite right about the pro-teams in Denver. But I'll say why I think it's different:

In the NFL, for example, a team will visit Denver perhaps once a year (possibly two if there is a play-off, or none, depending on conferences), and perhaps half a dozen times in baseball and basketball.

So the gaps between those trips are enormous. In a 72-match regular season for basketball, 6 matches is so tiny, and it's usually a batch of matches in a series, then back to sea-level.

In SA sport, the altitude alternates with sea-level on a weekly basis. So a coastal team would play one match at home (sea-level), then a match away (usually altitude - we have 5 altitude teams, 3 sea-level in rugby, for example). Then back to altitude.

So in a rugby season, our pro sports teams might play 16 matches, 7 of which are at altitude (counting playoffs). One week up, one week down, with only one or two exceptions where they go away to another sea-level team.

The demand is of course the same - any time you arrival at altitude, you feel it (as you did yourself!). But the logistics, and the cumulative demand sets SA apart, and that's because we have a) a small league, and b) more teams at altitude than at sea level.

Perhaps there is another place where this happens - South American football is probably worse in terms of altitude (Bolivia is 3,400m high!), but the frequency is again low!