| Study (first author, year and location) | Sport/activity | Study design and duration | Participant population | Injury definition and method of measurement | Outcome measure | Results (95% CI) |
| A: Prospective studies | ||||||
| Bjorkenheim, 1993, Finland39 | Ice hockey | Prospective cohort; one season | Competitors aged 9–18 years participating in a junior league (n = 1437) | Definition: any injury that prevented participation in at least one training session or game. Measurement: a questionnaire was completed by all team coaches and players at the end of each season | Injuries per 100 participants | <12 years, 0.9 (0.4 to 1.9); 12–15 years, 12.4 (9.8 to 15.4) |
| Brust, 1992, Minnesota, USA40 | Ice hockey | Prospective cohort; one season | Male competitors aged 9–15 years in a community-organised hockey program; results reported for age/weight divisions | Definition: any incident that resulted in a player not being able to continue to participate in a game or practice or that kept a player from participating in physical activities the following day. Measurement: injury forms were collected for each injured player by a number of means: team managers and coaches, players and parents and trained observers; telephone contact was made with a parent of each injured player 1 week after injury | Injuries per 100 player seasons | 9–11 years, 70 (54 to 82); 11–13 years, 32 (20 to 47); 13–15 years, 25 (14 to 40) |
| Goldberg, 1988, New England, USA41 | American football | Prospective cohort; one season | Competitors aged 8–15 years in Pop Wamer Leagues in 71 New England towns (n = 5128). Results extracted for age/weight divisions: jr peewee (8–11 years); peewee (9–12 years); jr midget (10–13 years); midget (11–14 years); jr bantam (12–15 years) | Definition: any incident causing over 7 days of missed activity; moderate, 8–21 days missed; major, >21 days missed. Measurement: coaches were responsible for keeping records of injuries; in addition, players were randomly contacted at end of season | All injuries per 100 player seasons; major injuries per 100 player seasons | All injuries: jr peewee, 1.9 (1.1 to 3.2); peewee, 2.7 (2.0 to 3.6); jr midget, 5.8 (4.7 to 7.1); midget, 8.4 (6.9 to 10.1); jr bantam, 9.6 (6.1 to 14.9). Major injuries: jr peewee, 0.7 (0.3 to 1.7); peewee, 0.9 (0.6 to 1.5); jr midget, 2.4 (1.8 to 3.3); midget, 3.3 (2.4 to 4.4); jr bantam,3.4 (1.6 to 7.2) |
| Gutgesell, 1991, USA42 | Basketball | Prospective cohort | Competitors aged 5–12 years competing in a YMCA program (n = 510 (406 boys, 104 girls)) | Definition: any injury; significant, unable to play for at least one session. Measurement: observers recorded all injury occurrences during games and practices | Injuries per 100 athlete exposures (games and practices); injuries per 100 participants; significant injuries per 100 participants | Injuries per 100 athlete exposures: 4.86 (3.58 to 6.58). Injuries per 100 participants: boys: 6.16 (4.22 to 8.93); girls: 13.46 (8.22 to 2.14). Significant injuries per 100 participants: 2.35 (1.36 to 4.07) |
| Kopjar, 1995, Stavanger, Norway43 | Bicycle riding | Prospective injury surveillance; 4 years | All children in Stavanger aged 10–15 years (n = 7256 ) | Definition: all bicycle-related injuries treated by Central hospital and emergency clinic. Measurement: bicycle use in population estimated from proportion of children who ride bicycles at least once a week | Per 1000 bicycle rides (to and from school); per 1000 bicycle users (other travel) | Per 1000 bicycle rides: boys: 10–12 years, 2.9 (1.9 to 4.4); 13–15 years, 6.8 (5.1 to 8.9); girls: 10–12 years, 3.3 (2.2 to 5.0); 13–15 years, 2.5 (1.6 to 4.0). Per 1000 bicycle users: boys: 10–12 years, 9.0 (7.1 to 11.5); 13–15 years, 14.6 (12.0 to 17.6); girls: 10–12 years, 6.4 (4.8 to 8.6); 13–15 years, 4.9 (3.5 to 6.8) |
| Kucera, 2005, North Carolina, USA44 | Soccer | Prospective cohort; four seasons | Competitors aged 18 years and younger registered with the North Carolina Youth Soccer Association (n = 7000) | Definition: any injury that resulted in a player being removed for part or all of a game and/or miss subsequent practices or games. Measurement: injuries were reported by team coaches by mailing injury cards detailing details of all injuries to the study investigators each week | Injuries per 1000 athlete exposures | U12–14 years, 3.6 (3.1 to 4.1) |
| Lee, 1996, Edinburgh, Scotland45 | Rugby | Prospective cohort | Competitors in schoolboy rugby (n = 1705) | Definition: any incident sustained on the field during match or training that prevented player from further participation. Measurement: an adult link-person at each school collected all relevant injury details; each injured player was then contacted directly by study personnel. | Injuries per 100 player seasons | 11 years, 1.53 (0.57 to 3.63); 12 years, 4.20 (1.87 to 6.52); 13 years, 4.64 (2.42 to 6.86); 14 years, 6.43 (3.76 to 9.08); 15 years, 8.89 (5.17 to 12.61) |
| Linder, 1995, USA46 | American football | Prospective cohort; two seasons | Competitors aged 11–15 years in junior high football (n = 340) | Definition: any sports-related mishap occurring during practice, drills, scrimmages or games resulting in removal from a practice or game and/or missing a subsequent game or practice. Measurement: injuries were recorded by each team coach, and then forwarded to study personnel on a weekly basis | Injuries per 100 player seasons | 8 (6.3 to 10.2) |
| Radelet, 2002, USA47 | Baseball, soccer, softball, American football | Prospective cohort; two seasons | Competitors aged 7–13 years in organised community sports (n = 1659) | Definition: any incident requiring on-field evaluation by coaching staff, first aid or that prevented further participation. Measurement: coaches collected data using a survey tool designed for study | Injuries per 100 athlete exposures (including games and practice) | Soccer, 2.1 (1.7 to 2.5); baseball, 1.7 (1.4 to 2.0); football, 1.5 (1.3 to 1.8); softball, 1.0 (0.7 to 1.3) |
| Roser, 1970, Seattle, USA48 | American football | Prospective observational cohort; one season | Competitors aged 9–15 years in Seattle Junior Football Program (n = 2079). Results extracted for league divisions: bee (9–11 years); midget (9–11 years); peewee (10–12 years); gil dobie (13–14 years); bantam (up to 15 years) | Definition: any incident causing no participation in either game or practice. Measurement: coaches completed injury questionnaires; parents were contacted for additional information | Injuries per 100 player seasons | Bee, 3.1 (1.8 to 5.7); midget, 2.3 (1.3 to 3.9); peewee, 2.3 (1.4 to 3.8); gil dobie, 1.4 (0.6 to 2.9); bantam, 3.3 (2.4 to 10.7) |
| Stuart, 2002, USA49 | American Football | Prospective cohort; one season | Competitors aged 9–13 years registered with community youth football (n = 42 teams) | Definition: any incident that either kept the player out of the remainder of the game or required doctor attention; all concussion, dental, and eye cases were included. Measurement: all injuries were reported by coaches; all injured players were examined by a doctor and details were taken during this examination | Injuries per 1000 player games; injuries per 1000 player plays | Injuries per 1000 player games: 8.47 (6.52 to 11.01). Injuries per 1000 player plays:0.17 (0.13 to 0.22) |
| Sullivan, 1980 Oklahoma, USA50 | Soccer | Prospective cohort; one season | Competitors aged 7–18 years registered with 2 clubs (80 teams) of the Frontier Country Soccer Association (n = 1272) | Definition: any medical problem occurring during games or practice that prevented further participation; major injuries, more than 7 days play or practice missed. Measurement: coaches reported which players had been injured, parents contacted for details; coaches were contacted weekly by study researchers | Per 100 player seasons | <8 years, 0.30 (0.08 to 1.67); 8–9 years, 1.23 (0.50 to 3.13); 10–11 years, 1.40 (0.62 to 3.23); 12–13 years, 5.11 (2.54 to 10.17); 14–15 years, 17.28 (10.62 to 26.98) |
| Turbeville, 2003, Oklahoma, USA51 | American football | Prospective cohort; two seasons | Competitors aged 10–15 years participating in middle school football (n = 646) | Definition: any injury that prevented further participation in game or practice or any head injury resulting in impaired consciousness. Measurement: coaches or athletic trainers recorded details of all injuries | Injuries per 1000 games; injuries per 1000 practices | Injuries per 1000 games: 8.8 (6.3 to 12.2). Injuries per 1000 practices 1.0 (0.7 to 1.4) |
| Yde, 1990, Denmark52 | Soccer, handball, basketball | Prospective cohort; one season | Competitors aged 6–18 years participating in a Danish sports club (n = 302) | Definition: an incident occurring during match or training in the club causing the player to miss at least one match or one training session. Measurement: all injured players were interviewed by the study investigators who visited the club weekly and registered all injuries | Injuries per 100 player seasons | Soccer: <10 years, 13.8 (7.5 to 24.3); <14 years, 51.2 (36.7 to 65.4). Handball: <10 years, 0; <14 years, 12.5 (4.5 to 31.2). Basketball: <10 years, 0; <14 years, 0 |
| B: Retrospective studies | ||||||
| Berger-Vachon, 1986, Rhone-Alpes, France53 | Soccer | Retrospective analysis of insurance claims data; one season | Competitors of all ages in Rhone-Alpes Soccer League | Definition: any incident reported to Rhone-Alpes Soccer Association insurance company. Measurement: all reports including doctor examination | Risk of injury per season; risk of injury per player per match | Risk of injury per season: 10–11 years, 0.6%*; 12–13 years, 0.9%; 14–15 years, 2.2%. Risk of injury per player per match: 10–11 years, 0.23%; 12–13 years, 0.33%; 14–15 years, 0.9% |
| Gugenheim, 1976, Houston, USA54 | Baseball | Examination of players for pitching elbow | Pitchers aged 9–13 years in the Little League Metropolitan – Houston area (n = 595 ) | Definition: any elbow discomfort during pitching career; minor, did not exclude player from game; major, player excluded from game. Measurement: injuries were retrospectively reported by players; each player reporting an injury was examined by a doctor | Risk of elbow injury per lifetime (1–8 years) | Minor, 17% (14 to 20%); major, 1% (0.5 to 2.2%) |
| Hale, 1961, USA55 | Baseball | Analysis of insurance reports; 5 years | Little League baseball players aged 8–12 years (n = 771 810) | Definition: any incident requiring medical attention and reported by doctor to insurance company. Measurement: medical reports submitted by doctors to a single insurance company | Injuries per 10000 balls pitched | 1.04* |
| Kujala, 1995, Finland56 | Soccer, ice hockey, volleyball, judo, karate | Analysis of insurance registry data; 5 years | All competitors in Finland with license from a sporting association (n = 621 691 person years) | Definition: acute sports injuries requiring medical treatment reported to the insurance company. Measurement: analysis of all national sports injury insurance forms | Injuries per 1000 participants per year | Soccer: 25 (24 to 26). Ice hockey: 36 (34 to 38). Volleyball: 12 (9 to 14). Judo: 30 (21 to 41). Karate: 31 (16 to 55) |
| Larson, 1976, Eugene, USA57 | Baseball | Analysis of players; one season | Competitors aged 10–12 years in Eugene Sports Association Little League (n = 120) | Definition: any elbow discomfort during pitching career; minor, did not exclude player from game; major, player excluded from game. Measurement: retrospective reporting by players; each player examined by a doctor | Rate of minor injury per 100 players per lifetime; rate of major injury per 100 players per lifetime | Rate of minor injury per 100 players per lifetime: 20 (14.5 to 29.0). Rate of major injury per 100 players per lifetime: 0 |
| Marshall, 2003, USA58 | Baseball, T-ball | Analysis of compensated injury claims; 3 years | T-ball (aged 5–8 years) and baseball (aged 7–12 years) competitors participating in Little League Baseball. | Definition: ball-related and facial injuries for which compensation claims were lodged with an insurance company. Measurement: analysis of insurance claims | Ball related injuries per 100 000 player seasons; facial injuries per 100 000 player seasons | Ball related injuries per 100 000 player seasons: T-ball, 2.1 (1.4 to 3.0); baseball, 44.6 (42.4 to 46.9). Facial injuries per 100 000 player seasons: T-ball, 0.07 (0.02 to 0.41); baseball, 4.5 (3.8 to 5.3) |
| Molsa, 2003, Finland59 | Ice hockey | Analysis of insurance claims; 1 year | Competitors aged under 20 years participating in club competition (13706 <12 years, 13363 12–14 years) | Definition: upper extremity injuries requiring medical treatment reported to the insurance company. Measurement: analysis of insurance claims | Upper extremity injuries per 1000 player years | <12 years, 1.5 (0.9 to 2.3); 12–14 years, 9.4 (7.9 to 11.2) |
*95% CI could not be calculated.