By Joel Provano

The Atlanta Journal-Constitution

Heat-related deaths among football players have tripled since 1994, with Georgia recording more than any other state, University of Georgia researchers say.

In the 15-year period before 1994, there was an average of one death per year nationwide; between 1994 and 2009 the number was almost three per year, according to the study, published in the International Journal of Biometeorology. Georgia had the most deaths of any state, with six.

Researchers found evidence that elevated morning temperatures and humidity may have contributed to the trend.

"In general, on days the deaths occurred, the temperature was hotter and the air more humid than normal local conditions," said Andrew Grundstein, a UGA climatologist and senior author of the study.

But Grundstein cautioned against assigning blame only to warmer temperatures and higher humidity, noting that players are much larger now than they were 30 years ago. Linemen, who are typically the largest players, accounted for 86 percent of heat-related deaths.

"We all want a single magic number to indicate the heat threshold," he said. "But so many factors contribute to heat stress that it's impossible to draw the line at a single temperature."

Other findings from the study:

• During the 30-year period from 1980 to 2009 there were a total of 58 deaths.
• More than half of the players became ill on days when practice ended before noon.
• Most of the deaths occurred in the eastern half of the U.S.
• The majority of deaths occurred in August.

In conducting the study, researchers built a database that included the temperature, humidity and time of day of each death, along with the height and weight of the players who died during practice sessions of heat-related illness. The study did not provide participation numbers for football, but a study by the Sporting Goods Manufacturers Association showed that participation in football  declined 16 percent between 2000 and 2010.