(Reuters) - Football needs more data on the links between heading the ball and dementia before restrictions on training are imposed, the chief medical officer of the global players' union FIFPRO said.
The issue of dementia in the professional game was sparked by the death of England's Nobby Stiles, who along with many of his 1966 World Cup-winning team mates, including Jack and Bobby Charlton, had been diagnosed with the condition.
Premier League managers have called for a ban on heading in training if research shows it leads to dementia, while the Professional Footballers' Association (PFA) has urged clubs, leagues and the FA to come up with techniques to monitor training and protect players.
"In the UK there is this call to reduce heading in training," Vincent Gouttebarge said during a webinar hosted by Morgan Sports Law. "From a scientific point of view, I am missing a lot of information.
"We do not know a lot about heading exposure in games and we know nothing about it in training. What is the safe threshold? Who is going to monitor headers?
"If you don't know how much it has to decrease, you don't give tools to players to know what they must do in training. If we know a player is allowed 500 headers per season for 10 years, that could provide guidance. But we do not have this data."
Neuroscientist Michael Grey, who is conducting a project to monitor ex-footballers for early signs of dementia, said guidelines needed to be put in place immediately.
"It's important we start somewhere," he said. "I agree we don't have scientific data to say where the threshold should be. But I think what we're doing now, where it's just a free for all, is not the way forward."
(Reporting by Arvind Sriram in Bengaluru; Editing by Peter Rutherford)