CAPE TOWN, South Africa -- The goalkeepers at next year's World Cup should consider their geography before getting on the field.
A study by Adidas shows altitude will have an impact of up to 5 percent on a ball's speed. That means a 20-yard free kick during the final at Soccer City in high-altitude Johannesburg will reach the goal line 5 percent faster than it would at Moses Mabhida stadium in Durban, which is at sea level, according to the study seen by The Associated Press.
That translates into a free kick traveling at an average of 78 mph at high altitude and 74 mph at sea level, the study says.
But if playing at high altitude has some drawbacks for goalkeepers, it also has its advantages. A goal clearance that travels 60 yards in Durban would travel 63 yards in Johannesburg. And free kick specialists will not be able to put as much spin on the ball because the thin air offers less grip to change course.
Among the 10 host stadiums, Soccer City stands at 5,558 feet. The beach-side Moses Mabhida stadium is at only 26 feet.
Other stadiums at altitude include Bloemfontein at 4,432, Pretoria at 4,364, Polokwane at 4,035 and Rustenburg at 3,783. In addition to Durban, Cape Town and Port Elizabeth are also coastal.
Many teams already have decided to establish their training camps at altitude, mostly in and around Johannesburg. It is easier for players to adapt coming down to sea level rather than moving up to altitude.
Adidas traditionally produces new balls for each World Cup and they invariably cause controversy since new technology almost always makes for a speedier ball that puts goalkeepers at a disadvantage. Keepers have complained that some balls also wobbled on long-distance drives, making them look foolish on some goals.
This time, Adidas is convinced the Jabulani, which means "to celebrate" in isiZulu, will sail true because small dots on the surface improve reliability in the air for "an exceptionally stable flight and perfect grip under all conditions."
For the fans, the new ball is a splash of color compared to the black-and-white Teamgeist ball used at the 2006 World Cup in Germany.
Adidas said the 11 colors not only represent the players in a starting lineup but also the 11 official languages and the 11 communities of the host country.
"This ball will unify us in this country," World Cup organizing chief executive Danny Jordaan said. "It carries a lot of hope for the future of this country."
Former Germany captain and coach Franz Beckenbauer remembers the days when the ball was made from leather and soaked up rain.
"You pulled a muscle because the ball was so heavy," he said.