New research has discovered that heading a football is far more dangerous than you may suspect.
Scientists at the University of Stirling detected direct and "significant" changes to a player's brain function immediately after heading a ball, following calls to address the impact of repeated head trauma during routine training.
World Cup winner George Cohen has called for the game to tackle the issue of head injuries, and described old-style leather footballs as "nasty".
A history of trauma
Former England and West Bromwich Albion striker Jeff Astle died in 2002 at the age of 59 having suffered from early on-set dementia, which a coroner found was caused by heading footballs and who gave the cause of death as "industrial disease".
A subsequent re-examination of Astle's brain found he was suffering from the neuro-degenerative brain disease chronic traumatic encephalopathy (CTE).
CTE can only be established following death and it has also been found in deceased American footballers, boxers and rugby players.
Researchers gathered evidence using 19 footballers, at whom they fired footballs from a machine designed to recreate the speed and force of a corner kick.
The players were tested on their brain function and memory before and immediately after the kick, and found that increased inhibition in the brain was detected after just a single session of heading.
Memory test performance was also reduced between 41% and 67%, with effects normalising within 24 hours.
Cognitive neuroscientist Dr Magdalena Ietswaart said: "In light of growing concern about the effects of contact sport on brain health, we wanted to see if our brain reacts instantly to heading a football.
"With large numbers of people around the world participating in this sport, it is important that they are aware of what is happening inside the brain and the lasting effect this may have."
Calls for change
Astle's daughter Dawn has been campaigning for more research into the matter and was told by the Football Association and the Professional Footballers' Association in late 2014 that they were talking to Fifa.
She has previously called brain injury as a result of heading a "silent scandal" and warned there is little evidence to suggest the newer, synthetic version of the once-leather football is better for players' health.
Cohen told The Daily Telegraph in June: "You felt sick sometimes when it hit you. They started out at 14 to 16 ounces but, with rain, they were two or three pounds.
"Even if it hit you on the side of the head, a graze, it was really uncomfortable. Those early balls were really rather nasty."