A potentially explosive study is expected to reignite the safety debate around heading footballs if evidence is found that players' brains are damaged by repeated head impacts.
The study, undertaken by researchers at Stirling University and set to be published on Sunday, is expected to claim changes to brain function can be caused by the everyday head impacts - also referred to as sub-concussive blows - associated with heading footballs.
The research team, led by cognitive neuroscientist Dr Magdalena Ietswaart, monitored a group of 19 players undertaking routine heading drills under laboratory conditions, before monitoring how they performed in memory tests.
It is believed evidence of temporary memory decline of about 60 per cent was found in some players. Although the effects returned to normal within 24 hours, the research team believe it could point to more significant lasting damage to players' brains.
The results of the study are set to reignite a debate in football and beyond about the long-term damage to players' brains caused by concussive and sub-concussive blows.
In 2002 former England and West Bromwich Albion striker Jeff Astle died aged 59 suffering from early on-set dementia which a coroner found was caused by heading footballs and gave the cause of death as 'industrial disease'.
A subsequent re-examination of Astle's brain found he was suffering from the neurodegenerative brain disease Chronic Traumatic Encephalopathy (CTE) that is also found in diseased former American foot-ballers, boxers and rugby players.
Dawn Astle, Jeff's daughter, told The Mail on Sunday: 'Would I be surprised if damaging effects of heading are found? No. The question is: what are they going to do about it? What are the authorities going to do to protect our children?
'These people are paid an awful lot of money to protect players and children playing football at any level. If they find damage is caused by heading the ball - which we as a family believed even before the coroner found dad's brain was damaged in the same way as a boxer's - then what are the long-term implications?
'Is this why, especially with ex-professionals who head the ball more, there are so many former players suffering from dementia?'
In 2014 The Mail on Sunday discovered a 10-year study promised by the Football Association and the players' union, the PFA, into the long-term effects of head injuries was never completed, leading to former FA chairman Greg Dyke issuing a public apology for his organisation's conduct and the promise to fund further research.
Astle's family - who set up the Justice for Jeff campaign after being alerted to the FA's failure to deliver their promised research - have subsequently established the Jeff Astle Foundation which helps support the hugely disproportionate number of former professional footballers suffering early on-set dementia in their 50s and 60s.
At least four of England's 1966 World Cup-winning team are known to suffer from dementia, while the Astle Foundation has been contacted by 'countless' families of former professional footballers who are suffering early on-set dementia they believe has been caused by head injuries sustained during their playing careers.
'The brain as an organ is the most fragile and complex organ in the body but if it's being pounded all the time and rocking backwards and forwards inside the skull you can only imagine the damage that is being done,' added Dawn Astle.
'Why did my dad die of boxer's brain when he wasn't a boxer? Sports governing bodies should not be protecting the product, they should be protecting the players.'
Last year US Soccer - the country's governing body - banned heading for children younger than 10, with juvenile brains known to be more susceptible to damage than adults. Practising headers between 11 and 13 is also monitored and the latest Stirling University study will reignite the debate about whether young children should be allowed to head the ball in the UK.
Football's governing bodies and some clubs in England have been heavily criticised for their treatment of concussion and head injuries in the sport, with guidelines over concussion often ignored, while some managers appear willing to over-rule medics in their desire to keep players on the field.
Liverpool team doctors are known to want to introduce the Myplay-Xplay real-time video technology used by rugby clubs in the Aviva Premiership to assess head injuries on the touchline but have been banned by the Premier League and FIFA under anti-competition rules.
A Liverpool source said: 'We are making the best of a bad situation when treating on-field injuries. We have the technology now to improve player care and safety, but it is being stifled by rules. From my perspective, if a rule puts a player's health at risk, then it is wrong.'
The FA published guidelines on concussion last year and insist they are working hard on the issue.
'The FA's medical work on head injuries in football has been ongoing for some time and we are focused on better understanding and implementing preventative measures for the safety of players, across all levels of the game,' said a spokesperson.
'We welcome any medical research in this area and this study gives an interesting insight into the short-term effects of heading the ball, which is important because this occurs uniquely in our sport.
'The FA is committed to researching and examining all areas of head injuries in football, in particular the long-term effects.
'We are currently assessing research projects in this area, in collaboration with the Drake Foundation and the PFA, and this will help us to fully understand the health benefits and any risks associated with playing football.'