The stage has been set to discuss altitude and its effects on football performance., Dr Ross Tucker weighs in.
I was just reading in a local paper that both Denmark and the Netherlands have blamed the altitude for their lacklustre performances in Johannesburg.
The impact of altitude on football is not as clear as its impact on running and cycling. My article on physiology painted a picture of 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 utilised as frequently and for the stature of event hosted here. We host European PGA golf events where the transition happens within three days. International rugby is played at sea-level with another match at 1,700m within a week. International cricket matches follow the same pattern. And now so does 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.
Altitude affects performance in various ways. Broadly, there are two effects. One is on the physiology, which is my focus here. The second is on the flight of the ball - reduced air density means faster, further and higher, as any golfer will tell you.
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 coincidence 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.,.
For football, the problem is that sprints are repeated over and over, with short recoveries. It's therefore a hybrid of the two extremes.
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.
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.