(CN) – With finalists for the 2018 World Cup ready to face off this weekend, a new study released Wednesday sheds light on the cumulative impacts “heading” the soccer ball has on the neurological functions of players.
John Jeka, a neurologist at the University of Delaware, said his research reveals soccer players who head the ball more often are more likely to develop balance problems when compared with players who use their head less during games.
"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," Jeka said. "But the effect of headers on balance control has not been studied."
For the study, Jeka pulled 20 soccer players from the community in Newark, Delaware, where the University of Delaware is based.
The participants volunteered to take a balance test, walking along a foam pad under two conditions – one with a stimulator that makes participants feel as though they are falling sideways and one without.
The galvanic vestibular stimulation used places electrodes behind the ear of each participant and stimulates nerves that send messages from the balance system in the inner ear to the brain, making people feel like they are moving when they are in fact still.
The 20 participants had an average age of 22 and answered questionnaires regarding how many times they headed the ball while playing soccer over the course of the previous year.
Jeka acknowledged relying on the memory of a given participant is a limitation of the study but asserted the data is valuable. He determined how many times each participant headed the ball over the year by asking them to estimate the number of headers taken in practice and a game and then multiplying those numbers by the amount of practices and games.
The amount of head balls ranged from 16 to 2,100, with participants averaging about 451 headers per year.
Jeka found those with the most of headers had the biggest problem with both foot placement and hip abduction during the walking test. These results indicate those who headed the ball most often had problems vestibular and balance recovery problems.
Foot placement problems increased by 9 millimeters for every 500 headers on average, according to the study.
"Soccer players must have good balance to play the game well, yet our research suggests that headers may be undermining balance, which is key to all movement, and yet another problem now linked to headers," said study co-author Fernando V. Santos. "It is important that additional research be done to look more closely at this possible link with balance and to confirm our findings in larger groups of people."
The results were presented Wednesday at the American Academy of Neurology's Sports Concussion Conference.
Jeka received support for the study from the National Institutes of Health.
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