Heading a soccer ball results in head accelerations of less than 10g whereas the minimum values for the development of sport-related concussion are 40-60g, writes Dr Paul McCrory. In contrast, head to head contact can generate enough of the forces required to cause brain injury as in any conventional head injury.
This has led for calls for the use of protective headgear for soccer players, but research has found that commercially available soft helmets have only a limited protective role in this setting.
It seems unlikely that subconcussive impacts such as seen in head to ball contact will cause chronic neurological injury, he says. Although head to head contact may cause concussive injury, it is both uncommon and unlikely to result in cumulative brain injury.
Most head to head contact is inadvertent, and coaching techniques and visual perception training may help in a few cases but is unlikely to eliminate this problem entirely. Soft shell helmets or head protectors currently do not have the capability to prevent concussive trauma and hence cannot be recommended, he concludes.