Footballers who head the ball are more likely to have balance problems, according to a study.
The impact of a ball bouncing off the skull is enough to affect the brain works, and repeated impacts could have lasting effects.
So, although England fans will be happy players Harry Kane and Dele Alli have scored with their heads in this World Cup – and wing-back Kieran Trippier often crosses the ball into the penalty box – it may not be such good news for the players' brains.
Players who head the ball more often are at risk of damaging the white matter in their brains, which can affect memory and thinking skills.
The researchers from the University of Delaware now say more studies need to be done to back up their findings.
England defender Kieran Trippier, who often crosses the ball into the penalty area for other players to head it towards the goal
A study on a group of 20 footballers with an average age of 22 tested their ability to walk in a straight line with their eyes closed.
In one part of the test the players wore equipment which simulated the feeling of falling sideways to see how well they corrected their balance.
Scientists compared the players' ability to walk straight with how often they each reported heading the ball during practice or matches.
'Headers can change the structure of the brain'
Players who head the ball more often are less able to correct their balance during the test, which the researchers put down to damage to the brain caused by headers.
The author of the study, John Jeka said: 'Soccer headers are repetitive subconcussive head impacts that may be associated with problems with thinking and memory skills and structural changes in the white matter of the brain.
'But the effect of headers on balance control has not been studied.'
The number of headers the players did in a year ranged from 16 to 2,100, with an average of 451 – players were asked to remember how often, on average, they headed the ball and how often they played.
Head impacts can cause brain damage in later life
Heading is common practice in football and is often used to score goals from corner kicks, but more concerns are being raised about minor head impacts in sport.
Studies have suggested repeated impacts – even if they don't cause concussion – can lead to brain damage and even Alzheimer's disease in later life.
Former England footballer