PARIS (AFP) - Statistics have now confirmed anecdote as fact: South American teams used to playing at high altitude have a major advantage over lowland opponents, according to a study published on Friday by the British Medical Journal (BMJ).
Oxford University researcher Patrick McSharry trawled through the scores of 1,460 international matches played at different altitudes in 10 countries in South America spanning more than a century.
The lowland countries were Brazil, Argentina, Uruguay and Paraguay, all of whose national stadia are at height of 60 metres (195 feet) or less, followed by Peru (90 metres, 292 feet) and Chile, whose stadium is at 520 metres (1,690 feet).
The four highland nations were Venezuela (1,000 metres, 3,250 feet), Colombia (2,600 metres, 8450 feet), Ecuador (2,800 metres, 9100 feet) and Bolivia (3,700 metres. 12,025 feet).
Altitude difference had a major impact on performance, McSharry found.
Teams that were used to playing at altitude scored more and conceded fewer goals as the height progressively increased.
Each additional 1,000 metres (3,250 feet) increased the goal difference by half a goal.
McSharry found that in the case of two teams from the same altitude, the probability of the home side winning averages 53 percent.
But this rose to an astonishing 82 percent for an altitude difference of 3,695 metres (12,008 feet), such as when Bolivia played sea-level opponent Brazil.
But it fell to just 21 percent when the altitude difference was minus 3,695 metres (minus 12,000 feet), i.e. when Brazil played at home to Bolivia.
High altitude is known to cause lack of oxygen, cold and dehydration, leading to breathlessness, nausea, dizziness and fatigue, and strenuous sport such as football can make the symptoms worse.
Coaches can help their side by factoring in a player's individual susceptibility to altitude sickness when making their selection, says McSharry.
World football governing body FIFA on Saturday relaxed their previous ban on international matches at altitude to 2,750 metres (9,022 feet) "without acclimatisation" a move that still blows the final whistle for games at La Paz in Bolivia and in the Ecuadorean capital Quito.
In May, FIFA originally slapped an unconditional ban on matches at 2,500 metres (8,125 feet) or higher after its medical committee advised that playing at such a height was neither healthy nor fair.
It also cited home-field advantage of high-altitude teams over visiting teams from lower altitudes.
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