New studies say "heading the ball" in a soccer game could cause concussions.
The European studies say doing it repeatedly can interfere with memory and concentration. The findings have caused controversy in the soccer world.
The statements have triggered soccer associations to issue counter-advisories. Critics say the studies were small and flawed.
The Canadian Soccer Association has sent out this statement:
"There is no conclusive scientific evidence that heading the soccer ball causes concussions. Further research is necessary...to separate fact from speculation."
Dr. Rudi Gittens, who wrote the statement, says players need to explore the proper way to head the ball.
"My instincts, having played soccer and having headed the ball many times, tell me that if it's properly done then the risk is minimal."
According to some coaches, this is the proper technique:
- attack the ball
- keep your eyes open
- head through the ball with the centre of the forehead
The problem is coaches tend to teach based on experience, not science. So FIFA, the world soccer governing body, has commissioned Canadian researchers to examine the mechanics of heading the ball.
"What we hope to be doing is actually providing better guidelines to train the technique of heading the ball," says Marc Busenberg of Biokinetics which is doing research for FIFA.
Scientists will use a computer model to simulate heading as it's now taught. It will measure the load on the head when the skull meets the ball.
The researchers will then test whether players can reduce the impact by changing their technique.
The research will help coaches teach kids how to play it safe.