A new study by Adidas has found altitude could have up to five percent impact on the ball's speed at the 2010 FIFA World Cup.

According to the study, a free kick from 20 yards at the Soccer City stadium, in high-altitude Johannesburg, will reach the goal line five percent faster than it would at the Nelson Mandela Bay Stadium in sea-level Port Elizabeth.

David Beckham once smashed home a 97.9mph effort against Chelsea in the Premier League in February 1997. If he managed a repeat at one of South Africa's high altitude venues the ball would be pushing 103mph.

However it's not all bad news for goalkeepers, as a goal clearance that travels 60m in Port Elizabeth will go 63m in Johannesburg. Interestingly, free-kick specialists will lose out as spin on the ball will reduce as the thin air offers lesser grip to change course.

South Africa has five stadiums above 1000m, including Johannesburg at 1694m, Bloemfontein at 1351m, Pretoria at 1330m, Polokwane at 1230m and Rustenburg at 1153m. The remaining three stadiums are in Durban, Port Elizabeth and Cape Town which are all at sea level.

The effects of altitude have always been a long standing bone for contention in world sport. The 42,000-seater stadium, Estadio Hernando Siles, in Bolivia stands at 3637m above sea level and has regularly courted controversy.

In May 2007, FIFA declared a ban on World Cup Qualifying matches at stadiums above 2500m above sea level. However after a month long Bolivian dispute, FIFA raised the limit to 3000m and granted the Estadio Hernando Siles stadium a special exemption.

Since then, Bolivia have further exposed the effects of altitude, inflicting Argentina's worst defeat in 60 years, thrashing them 6-1 in April 2009 and more recently beating Brazil 2-1.

Posted on 11/12/2009