Objective Based on the assumption that professional hockey is violent and that this influences the behaviour of children viewing it on TV, we investigated whether the absence of televised National Hockey League ice hockey games during a 1-year lockout reduced the rate of injuries of minor league hockey players in Canada.

Methods This natural experiment enabled us to use a quasi-experimental design to compare injuries suffered during the NHL lockout year with those in the seasons before and after. Data regarding the injuries came from a Canadian injury surveillance program (CHIRPP) while denominators, total numbers of registered players, came from Hockey Canada.

Results During the prelockout year the number and rates of injuries were as follows: 2153 (7.1, 95% CI 6.8 to 7.4, per 1000); during the lockout season they were 2215 (7.4, 95% CI 7.1 to 7.7, per 1000); and during the following year they were 2262 (7.0, 95% CI 6.7 to 7.3, per 1000). There were more severe injuries (concussions or fractures of long bones) and more injuries due to penalised acts during the NHL lockout year but the differences were not statistically significant.

Conclusions These findings suggest that children are not influenced by viewing professional hockey. It may even be the case that when young players are not exposed to the consequences of aggressive play resulting in severe injuries etc. they become less fearful and more aggressive.