The research is published July 17 in the open access journal PLOS ONE by Michael Cusimano and colleagues from the Injury Prevention Research Office at St. Michael's Hospital, Canada.

The authors compared reports hockey players suffering concussions in the National Hockey League (NHL) before and after rules regulating head contact were changed in 2010-11 and 2011-12. Based on official game records and team injury reports, the authors found that the number of NHL concussions or concussion-like head injuries in 2009-10 were lower than in the 2010-11 and later seasons. Sixty-four percent of the concussions were caused by body-checking, while only 28% were caused by illegal incidents.

The authors conclude that rules regulating body-checking to the head did not reduce the number of players suffering concussions, so additional changes or stricter enforcement of existing rules may be required to reduce the risk of these injuries further.