Intervention group (bodychecking not allowed): Mean 9.1 penalties per game in the regular season, 6.8 per game during tournaments

Comparison group (bodychecking allowed): Mean 12.4 penalties per game in the regular season, 8.2 per game during tournaments

Penalties for hostile aggressive behaviour were more frequent in games played with bodychecking than in those played without bodychecking (average increase 2.9 and 1.6 penalties per game for regular season and tournament play, respectively) (p < 0.05)

Intervention group: 7 injuries (1 fracture) in 263 games

Comparison group: 26 injuries (14 fractures) in 315 games; 1 fracture per 22.5 games; injury rate was 12 times greater than in intervention group (p value not reported)

88% of all fractures were related to bodychecking (p value not reported)

Peewee league: Mean 4.5 penalties per team per game, and 1.2 major penalties per team per season; 1 fewer penalty per game on average than in comparison group (p value not reported)

Bantam league: Mean 7.8 penalties per team per game; fewer penalties than in comparison group (p value not reported)

Bantam league: 30% fewer major penalties and 25% fewer game suspensions than in comparison group (p value not reported)

Peewee league: Mean 5.7 penalties per team per game, and 6.4 major penalties per team per season

Bantam league: Mean 8.4 penalties per team per game

Intervention group (Fair Play rules): 7.1 penalties per game

Comparison group (regular play): 13.0 penalties per game; there were 4 times more penalties related to rough play than in the intervention group (p value not reported)

Intervention group: 5.7 notable injuries (> 1 d of play lost, facial laceration or concussion) per 1000 player-exposures

Comparison group: 27.6 notable injuries per 1000 player- exposures

Ratio of notable injuries per 1000 player-exposures in regular games to such injuries in games following Fair Play rules was nearly 5:1 (p value not reported)

Intervention group: 669 body-contact penalties per game and 498 stick-related penalties per game after introduction of rule disallowing checking from behind

Comparison group: 762 body-contact penalties per game and 695 stick-related penalties per game before introduction of the rule

Significantly lower rates for body-contact and stick-related penalties after introduction of the rule (p < 0.001)

Intervention group: 16 head/neck injuries per 1000 player- games and 16 back injuries per 1000 player-games

Comparison group: 26 head/neck injuries per 1000 player-games and 21 back injuries per 1000 player-games

Rates of head/neck and back injuries decreased significantly after introduction of the rule (p < 0.001)

Intervention group (Fair Play rules): 3195 transgressions recorded

Comparison group (regular play): 8076 transgressions recorded

Significantly fewer penalties per game in the intervention group (p < 0.01)

Intervention group: 1730 (37%) of 4736 hockey-related injuries were in Quebec, where bodychecking was not allowed until Bantam level (14–15 yr)

Comparison group: 3006 (63%) of 4736 hockey-related injuries were in Ontario, where bodychecking was introduced at the Peewee level (12–13 yr), and at the Atom level in competitive leagues (10–11 yr) in certain jurisdictions

Most of the injuries (3618 [76.4%]) occurred in games where bodychecking was allowed

Players aged 10–13 yr in leagues that allowed bodychecking were at increased risk of a bodychecking-related injury (OR 2.65, 95% CI 2.21–3.18); they were also at increased risk of concussion (OR 1.53, 95% CI 0.93–2.52) or possibly a fracture (OR 1.20, 95% CI 1.00–1.47)

Intervention group (bodychecking not allowed): 40.6 injuries per 1000 players; 33 (40.2%) of players had severe injuries

Comparison group (bodychecking allowed): 85.5 per 1000 players; 77 (51.0%) of players had severe injuries

The overall injury rate was significantly greater in the comparison group than in the intervention group (rate ratio 1.9, 95% CI 1.4–2.6); the rate of severe injuries was more than 2 times greater in the comparison group (rate ratio 2.4, 95% CI 1.6–3.6)

Intervention group (after the Bertuzzi incident): Mean 5.2 aggressive infractions per game, 60 fighting infractions and 2 game-misconduct infractions

Comparison group (before the incident): Mean 6.5 aggressive infractions per game, 91 fighting infractions, and 22 game- misconduct infractions

Slight but nonsignificant reduction in the frequency of aggressive behaviours after the incident (p = 0.3)

When individual acts of aggression (e.g., slashing, fighting) were examined independently, infractions for fighting and game misconduct significantly decreased after the incident (p < 0.05)

Intervention group (bodychecking not allowed): 1.37 injuries per 100 players per season (95% CI 0.17–4.89); 0.43 injuries per 100 player-hours

Comparison group (bodychecking allowed): 24.64 injuries per 100 players per season (95% CI 17.71–32.69); 3.16 injuries per 100 player-hours

Relative risk of injury considering exposure-hours was 4.89 (95% CI 1.54–24.9) in the comparison group; however, attitudes toward bodychecking, empathy and aggression did not influence injury rates

Intervention group (bodychecking not allowed): 91 injuries (23 concussions) reported during 82 099 player exposure-hours

Comparison group (bodychecking allowed): 241 injuries (78 concussions) reported during 85 077 player exposure-hours

The risk of any game-related injury and of concussion or other severe injury was 3-fold greater (95% CI 2.31–4.60) in the comparison group than in the intervention group

Intervention group: Before the rule change (to lower the age when bodychecking is introduced), the overall injury rate was 59.9 injuries per 1000 player-years (95% CI 55.4–64.4)

Comparison group: After the rule change, the rate was 49.1 injuries per 1000 player-years (95% CI 44.8–53.3)

Contrary to hypothesis, the overall injury rate decreased after the rule change (p value not reported); the overall rate of injury and concomitant neurotraumatic events did not increase (p value not reported)

Intervention group: Before the rule change (to lower the age when bodychecking is introduced from the Peewee level to the Atom level), there were 1617 injuries overall (158 at the Atom level)

Comparison group: After the rule change, there were 2843 injuries overall (243 at the Atom level)

The odds of a bodychecking-related injury were significantly increased after the rule change in all divisions (OR 1.26, 95% CI 1.16–1.38) and at the Atom level (OR 2.20, 95% CI 1.70–2.84)

Rates of injuries involving the head and neck (OR 1.52, 95% CI 1.26–1.84) and shoulder and arm (OR 1.18, 95% CI 1.04–1.35) increased most substantially

Intervention group: 272 injuries (51 concussions) were reported during 96 907 player-hours among players with previous bodychecking experience

Comparison group: 244 injuries (49 concussions) were reported during 85 464 player-hours among players without previous bodychecking experience

The adjusted incidence rate ratio for game-related injury and concussion overall between players with previous bodychecking experience and those without it were as follows: injury overall 0.85 (95% CI 0.63–1.16), concussion overall 0.84 (95% CI 0.48–1.48) and injury resulting in more than 7 d of lost play 0.67 (95% CI 0.46–0.99)

The rate of injury resulting in loss of on-ice time was reduced by 33% among players who had 2 years of bodychecking experience compared with players who had no previous bodychecking experience

Intervention group: After use of the self-supervision strategy for coaches, only 1 of the 4 Quebec third-tier leagues showed a significant reduction in the number of penalties per game (mean 9.0 before v. 8.1 after strategy; p < 0.001). In terms of minor aggression penalties per game, this Quebec league showed a significant reduction (mean 5.9 before v. 5.4 after strategy; p = 0.02); however, the Ottawa top-tier league showed a significant increase (mean 4.7 before v. 5.2 after strategy; p = 0.02). The Quebec top-tier and Ottawa third-tier leagues showed no significant difference with the strategy

Comparison group: The Franc-Sud third-tier Quebec league showed a significant decrease in the number of penalties per game the next year without using the strategy (mean 8.4 per game in 1987/88 season v. 7.4 per game in 1988/89 season; p = 0.009); this team showed no significant change in the no. of minor aggression penalties per game

Significant decrease in no. of penalties only in the Quebec third-tier league (p < 0.001)

Significant decrease in no. of minor aggressive penalties in the Quebec third-tier league (p < 0.02), but significant increase in Ottawa top-tier league (p < 0.02)

Intervention group: Two leagues using the strategy experienced a mean decrease in the no. of minor injuries per game per team (Ottawa top tier: mean 0.6 before v. 0.5 after strategy; Ottawa third tier: mean 0.8 before v. 0.6 after strategy); the other 2 leagues using the strategy experienced a mean increase in minor injuries per game per team (Quebec top tier: mean 1.0 before v. 1.6 after strategy; Quebec third tier: mean 1.1 before v. 1.7 after strategy)

Comparison group: The Franc-Sud third-tier league had a mean of 1.4 minor injuries per game in the 1988/89 season

The proportion of major injuries related to bodychecking decreased from 75.0% to 68.7% after the strategy

The strategy had no significant effect on the no. of minor injuries in all leagues

Bodychecking was the main cause of all minor injuries during both seasons (in 46.2% of injuries in the 1987/88 season and 46.7% in the 1988/89 season)

Intervention group (Smart Hockey video): The total no. of penalties per game did not change significantly among players after they watched the video (p value not reported); however, the mean (± SEM) no. of penalties per 1000 player-hours decreased significantly (p < 0.05) for cross-checking penalties (from 23.7 ± 1.3 to 13.0 ± 3.4) and for penalties for checking from behind (from 38.4 ± 3.7 to 7.6 ± 0.7)

Comparison group (no video): The mean (± SEM) no. of penalties per 1000 player-hours significantly (p < 0.05) decreased for interference penalties (from 50.0 ± 5.0 to 28.4 ± 5.7) and increased for holding penalties (from 12.5 ± 2.5 to 22.7 ± 0.0)

Overall, the total no. of penalties did not change significantly after watching the video (p value not reported)

Intervention group: In the 2007/08 season, 4 yr after HEP was implemented, the mean no. of penalties per 100 games was 310 tactical penalties, 205 minor penalties, 15 major penalties and 40 other penalties

Comparison group: In the 2004/05 season, the first season after HEP was implemented, the mean no. of penalties per 100 games was 230 tactical penalties, 275 minor penalties, 80 major penalties and 140 other penalties

The penalty rate decreased across all 4 seasons in all 4 sectors (tactical, minor, major, other) (p value not reported)

The percentage of Fair Play points increased across all 4 seasons (p value not reported)

Intervention group: During the aggression-management training, the no. of penalty minutes per game was 1.67 for player 1, 0.00 for player 2 and 0.286 for player 3; after the intervention, the mean no. per game was 1.32 for player 1, 0.947 for player 2 and 1.0 for player 3

Comparison group: Before the training, the mean no. of penalty minutes per game was 2.00 for player 1, 1.4 for player 2 and 1.18 for player 3

Each player had a reduction in penalty minutes during and after the training; overall, the percentage of penalty minutes decreased after the training (p value not reported)

Intervention group: After the Playing Clean and Tough Hockey Program, the mean no. of aggressive acts per game was 3.92 for player 1, 3.90 for player 2 and 4.90 for player 3; for major aggressive acts, the mean no. per game was 1.00 for player 1, 1.70 for player 2 and 2.70 for player 3

Comparison group: At baseline, the mean no. of aggressive acts per game was 4.00 for player 1, 4.42 for player 2 and 6.75 for player 3; for major aggressive acts, the mean no. per game was 1.25 for player 1, 2.25 for player 2 and 4.58 for player 3

Overall, the ability to manage emotions increased and aggressive-behaviour variables decreased after the program for 2 of the 3 participants (p value not reported)