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A prospective cohort study of the incidence of injuries among junior Australian football players: evidence for an effect of playing-age level
  1. M Romiti1,
  2. C F Finch2,
  3. B Gabbe3
  1. 1
    NSW Injury Risk Management Research Centre, University of New South Wales, Sydney, Australia
  2. 2
    School of Human Movement and Sport Sciences, University of Ballarat, Ballarat, Australia
  3. 3
    Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, Australia
  1. Professor C Finch, School of Human Movement and Sport Sciences, University of Ballarat, PO Box 663, Ballarat Victoria 3353, Australia; c.finch{at}ballarat.edu.au

Abstract

Objective: To determine the rate of injury in junior Australian football, and to describe the patterns and severity of these injuries across nine levels of play (U9 to U18).

Design: Prospective cohort study.

Setting: Junior Australian football games and training sessions were observed for 54 teams from New South Wales and Victoria over the 2004 playing season.

Participants: Six teams from each level of play were invited to participate in the study. Overall, data were collected for 51 teams over 40 208 hours of player exposure.

Independent variables: Participation and injury data were collected prospectively.

Main outcome measures: Injury was defined as “any trauma that causes some disability or pain”. Injury severity was identified by the action of players immediately after the injury event.

Results: The overall injury rate was 18.0 (95% CI 16.6 to 19.3) injuries per 1000 player hours. The main cause of injury was body contact (67.3%). There was an increased frequency of sprains and strains, and injury severity with increasing level of play. The rates of injury for players who stayed off the field (6.4 injuries per 1000 hours, 95% CI 5.6 to 7.2) or were advised to seek off-field medical advice (5.0 injuries per 1000 hours, 95% CI 4.3 to 5.7) were low.

Conclusion: Compared with the adult game, junior Australian football is relatively safe. However, injury rates increase as children progress across age-determined levels of play towards the more adult form of the game.

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A major hindrance to the promotion of sporting activity among children for improved health is the risk of injury, prompting widespread comment in the literature.14 Injury prevention and safety policies are essential for attracting and maintaining participation of juniors in sport,5 particularly in contact sports such as football6 7 where parental perception of injury risk has been identified as a barrier to children’s participation.8

Australian football is one of the most popular participation sports among Australian children.9 The sport involves a high degree of “intentional” and “incidental” body contact, through the tackling of players and contesting the ball in flight or on the ground. Modified versions of Australian football have been developed to cater for the lower skill level of young participants and are used widely in junior competitions. These modifications include reduced field size, fewer players on the field, smaller and softer ball design, restriction of body contact and shorter game duration.10 11 Game modifications are progressively eliminated as the age group (level of play), increases.

In contrast to extensive research in adult Australian football players, particularly at the elite level,12 13 there has been limited research in juniors. To date, only two studies have investigated the injury patterns of community-level junior players.14 15 The earliest study15 was important for its demonstration of the effectiveness of rule modification, but only involved three levels of play and the study was performed over a decade ago. The more recent study14 included more levels of play, but exposure estimates and injury rates were not reported in the general standardised manner (per 1000 hours exposure).

Investigation of injury rates and patterns in junior Australian football is important for the identification of emerging issues and evaluation of injury prevention strategies, such as modified rules and development programmes. The purpose of the Junior Australian Football Safety Study (JAFSS) was to quantify injury risk and identify injury trends across all levels of junior players over a competitive season, and to identify opportunities to improve safety through targeted skill-development programmes.

METHODS

Ethics approval was granted from the University of New South Wales and Monash University. Participant information sheets were distributed to players and parents. Informed consent from players was not obtained as data were collected on an observed-game basis, without individual player follow-up.

Participants

Three football associations (two in Sydney, New South Wales (NSW) and one from Melbourne, Victoria), were asked to nominate potential clubs/teams to participate in the study over the 2004 football season. Six teams from each level of play: Under 9 (U9), U10, U11, U12, U13, U14, U15, U16 and U18, evenly divided across states, were recruited. Owing to the late withdrawal of two NSW teams, additional teams were recruited from Victoria.

Data collection procedures

Each team nominated a primary data collector (PDC) who attended all team training sessions and games for the season. Most PDCs were coaches, parents, team managers or sports trainers. A training seminar was provided to instruct PDCs on data collection methods and procedure manuals, including standardised data collection forms, were issued. Data collection commenced at the season’s first game and concluded at the final game for each team.

The PDCs recorded information on two forms: a participation form and an injury incident report form, adopted from a previous community-based Australian football study.16 Forms were completed at the time of injury and at the training session or game, to avoid the potential for recall bias.

Exposure data

The participation form indicated the number of players actively participating in each game and training session. Training sessions which involved activities of a non-football nature, eg swimming pool sessions, were excluded. The PDCs indicated the length of each training session. Game duration was obtained from the association’s game laws. The number of participants in any given session, along with game or training duration, formed the basis for the calculation of exposure:

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Total exposure (time) = game exposure + training exposure

Injury data

The definition of injury used in this study was “any trauma causing disability and/or pain”, adopted from McMahon et al.15 Documented injury data included the injury region, nature, cause and severity, and a text narrative of the injury event. Overuse and recurrent injuries associated with football were included only when first reported. Non-football injuries, insect stings, “breathing difficulty”, and fatigue-related exhaustion cases were excluded. Where multiple injuries were sustained in a single event, all injuries were documented. Injury causes were grouped into broader categories with similar injury mechanisms.

As players were not identified, common methods used to determine injury severity, such as missed participation and medical confirmation of injury diagnoses, were not possible. Therefore, the immediate action of, and advice offered to injured players were used to rank injury severity. These severity measures were the player: leaving the field, staying off the field, being advised to seek off-field medical advice, and being taken to hospital. Each of these post-injury events were recorded by the PDC at the time of the injury, or soon thereafter. These injury severity measures were used to determine the significance of injuries sustained, combined with the rate of injury.

Analysis

Each team’s game and training participation data were checked, coded and entered into a Microsoft Excel spreadsheet. Games and training injury incidence were calculated per 1000 hours of player exposure. Injury rates and injury rate ratios (IRR) were calculated in Microsoft Excel with 95% CI.

All injury details were entered into a Microsoft Access database. Data were verified by cross-checking the consistency of each injury variable with narrative descriptions for each injury report. Injury records with incomplete or conflicting information were identified and discussed between investigators before data entry proceeded.

RESULTS

Of the 54 teams recruited, 3 failed to record any exposure or injury data (94.4% study compliance). In total, 741 games and 1015 training sessions were recorded, resulting in a total of 40 208 hours of player exposure. Overall, 722 injuries were observed, of which 637 (88.2%) occurred during games. Information was provided on the injury incident report form for 715 injuries (99.0%). In 19 injury events, 2 injuries were sustained, and 1 event resulted in 3 injuries.

The overall rate of injury was 18.0 (95% CI 16.6 to 19.3) injuries per 1000 hours of exposure. The injury rate for NSW teams was 18.8 (95% CI 16.5 to 21.1) injuries per 1000 hours compared with 17.5 (95% CI 15.9 to 19.1) injuries per 1000 hours in Victoria. As there was no significant difference in the injury rates between states, all data were combined.

Injury rate ratios indicated that there was a significantly lower injury rate in U10, U12, U14, U15 and U16 levels, compared with the U18 group (table 1). Overall, there was a twelve-fold increased risk of injury in games compared with training.

Table 1 Injury rates in junior Australian football players per 1000 hours of exposure for all injuries causing disability and/or pain

Figure 1 illustrates the game and training injury rates across all levels of play. There was a trend towards increasing injury incidence with level of play, particularly from game injuries. The U18 level of play had a significantly higher rate of game injuries than all other levels, with 76.6 (95% CI 65.6, 87.7) injuries per 1000 hours. All levels of play had significantly lower training injury rates compared with games.

Figure 1 Game and training injury rates according to age-determined level of play in junior Australian football players (for injuries defined as “any trauma causing disability and/or pain”).

Figure 2 illustrates the injury rate according to the injury severity indicators for the 688 injuries with specified outcomes (yes/no) for all four severity measures. Significant differences were apparent between various severity indicators, except between players who stayed off the field and those advised to seek off-field medical advice. This suggests that most of the players who did not return to play were likely to require medical assistance.

Figure 2 Severity of injuries reported in junior Australian football (game and training combined) reported as rates per 1000 hours.

Injured region

Injuries to the leg (41.5% of all injuries) were almost twice as common as injuries to the arm (22.8%) or head, face and neck (22.1%). More specifically, the knee was the most common region of injury (12.9% of all injuries), followed by the ankle and hand/fingers (both 11.2%). Injuries to the face (10.3%), upper leg (10.2%) and head (9.2%) were also common.

The three most common regions of injury by level of play are shown in table 2. Injuries to the knee and hand/fingers were most common, and among the top three injured regions for seven of the nine levels of play. Other commonly injured sites among younger players were the face (U9, U10, U11, U12, U13, and U14) and head (U9, U11 and U12), whereas the upper leg was more commonly injured in older age players (U15, U16 and U18).

Table 2 Injuries sustained by junior Australian football players across age-determined levels of play

Injury nature

Almost a third of all injuries were haematomas/bruises (30.2%) followed by joint sprains (23.8%) and muscle/tendon strains (10.0%). Several minor injuries were reported, such as abrasions (7.9%), cuts/lacerations (6.7%) and epistaxis (4.0%). There were 17 (0.02%) fractures (excluding stress fractures).

The most commonly injured regions were assessed for predominant injury nature. Most knee injuries were sprains (31.5% of knee injuries), haematomas/bruising (26.1%) and abrasions (22.8%). Hand/finger injuries were most often reported as sprains (58.8% of hand/finger injuries) and haematomas/bruises (18.8%). Joint sprains were the most common ankle injury (78.8% of ankle injuries). Concussion (21.2% of head injuries) and bruising (19.7%) occurred with similar frequency for head injuries.

Across all levels of play, haematomas/bruises and joint sprains were most common (table 2). Minor injuries such as cuts/lacerations (U10 and U14) and abrasions (U9, U11 and U12) were more common in lower levels of play. Conversely, muscle/tendon strains were common in higher levels of play (U13, U15, U16 and U18). Over a third of all fractures reported (35%) were sustained by players at the U18 level.

Causes of injury

Over two-thirds (67.3%) of injuries were caused by body contact (table 3). A higher frequency of injury occurred to players in attacking play, such as being tackled (23.6%) and struck/hit while attacking (12.7%). Other contact (eg, ball/ground/goalposts) contributed to 11.7% of injuries, and 10.5% of injuries were associated with game movements, such as twisting, accelerating/decelerating and landing from a jump.

Table 3 The distribution of specific injury causes in injured junior Australian football players

Being tackled was the first or second most common cause of injury for all levels of play (table 2), and being struck/hit while attacking was also common among most levels of competition. Injuries due to collisions with another player/umpire, featured in the U10, U11, U13, U15 and U18 levels of play.

DISCUSSION

This study is the first to quantify fully the injury risk across all levels of play of junior Australian football, using collection of standardised exposure and injury data at games and training sessions. Although injury rates among some junior Australian football players have been previously described,15 these were determined over a decade ago across limited levels of competition.

Notwithstanding injury definition discrepancies, our results indicate that participation in junior Australian football is relatively safe compared with recent studies of community-level adults17 18 and elite adult players.12 The injury rate was significantly higher than that reported by McMahon et al,15 but our study involved a broader range of competition levels and older players. Our description of injury trends is inclusive of all injuries, using a broad definition indicating a more accurate rate of injury occurrence.19

The risk of injury at the U10, U12, U14, U15 and U16 levels of play was significantly lower than that of the U18 competition, as determined by IRRs. These lower injury rates are likely to reflect the effectiveness of gradual game development for skill progression among young players. Our stratified cohort approach permitted the investigation of possible injury differences with the gradual phasing-out of modified rules, although a larger sample of teams at each competition level might have indicated clearer age-related trends. The fact that U9 players had an injury rate not significantly different to the U18 players reflects the general nature of our broad injury definition and not injury risk.

The significantly higher game injury rate among players at U18 level identifies them as a priority group to reduce injury risk. This finding is particularly concerning, as players at this level are participating in the adult form of the sport, for which they may not be adequately prepared. Other factors such as risk-taking behaviours20 21 and physical maturity22 may also contribute to their increased risk, although playing experience and injury history have been shown to be better predictors of injury.23

Severity indicators showed that the rate of injuries where the player could not continue play or return to participation shortly after the injury incident were substantially lower than the overall injury rate. Fewer than a third of all injuries were advised to seek off-field medical advice, whereas previous research reported that approximately half of all injured adult community-level Australian football players sought treatment from a health professional.18

The most commonly injured sites in this study, especially the leg, are consistent with injury patterns among adult players.12 17 24 Proximal leg injuries, such as hamstring and groin strains, were more common among players in the U15–U18 levels of play, consistent with adult football studies.12 17 24 The increased frequency of lower limb injuries with level of play may be explained by a number of factors including higher impact forces with increased physical development and skill,25 26 increased game speed,27 and increased exposure time,23 28 although further investigation is recommended.

Poor gross motor and spatial awareness skills may explain the high incidence of facial, head and hand/finger injuries in lower levels of play, also reported previously.14 15 Head and facial injuries may support the use of personal protective equipment, although the effectiveness of head protection among Australian football players has not yet been shown.29 Although modifications to ball design have been implemented,30 further skill development to decrease hand and finger injuries is warranted.

The high incidence of injury from body contact, particularly through the tackle, indicates this as a priority area for injury prevention. Enforcing tackle regulation, and encouraging additional skill and technique development, should be considered. Even though intentional body contact is regulated through rule modifications, incidental contact such as player collisions can still lead to contact injuries. Although the injury rate during training was significantly lower than that during games, specific skill development at training sessions, such as bracing, proprioceptive, co-ordination and perturbation drills and safe falling techniques, designed to prevent injury, may translate to a decreased rate of game injuries.3133

Unfortunately, methodological and ethical constraints regarding the identification of players limited the ways in which we could determine injury severity, as we were also unable to confirm the medical diagnoses or treatment of injuries. The subjective nature of our injury definition is likely to have resulted in some reporting disparity particularly concerning minor injuries where pain and disability are not often evident. Our definition, however, is consistent with the study of McMahon et al,15 deeming injury rate comparisons with the earlier study valid.

Although the reliability of PDCs to accurately report injury data has not been fully reported,34 their collection of exposure and personal protective data has been validated.35 Our methods, which required PDCs to record injury data based solely on their observations of injury events without player contact, limited the certainty with which the true injury nature could be identified.34 Nevertheless, we believe that our injury severity markers provided adequate indication of the seriousness of reported injuries.

Future suggestions

Despite rule modifications in junior Australian football competitions, body contact was the most common cause of injury across all levels of play. Efforts should be made to improve junior players’ ability to cope with both intentional and incidental contact. Education and awareness of risk taking behaviour and safe use of contact may also assist in reducing the high game injury rate at U18 level.36 Additionally, coaches should be informed about the benefits of training methods for injury prevention and development of players to more effectively handle the demands of body contact.

What is already known on this topic

  • Although modified rules are commonly used in junior Australian football, few studies have investigated the epidemiology of injuries among young players.

  • There is a general increase in injury rate as players progress to higher age groups (or level of play).

  • However, previous investigations have had used limited age groups or non-standardised rate calculations.

What this study adds

  • This study demonstrates that the rate of injury among junior Australian footballers is substantially lower than that in adults.

  • This suggests that modified rules and junior game development strategies have been effective in reducing the risk of injury in young players.

  • Injury incidence, particularly during games, increases with age-determined level of play.

  • Injuries sustained at the higher levels of play (U18) are more serious in nature than those in younger players, and have a similar profile to those in adults.

  • Although rule modifications decrease the risk of injury through intentional body contact, it is recommended that junior game development includes training to improve the ability to handle incidental body contact.

CONCLUSION

Junior Australian football, particularly among the lower levels of play, is relatively safe compared with the adult game. Low injury rates suggest that modified game rules and regulations are an effective method of reducing injury rates among children. The higher rate of injury demonstrated among players at the U18 level where adult rules apply, is comparable to injury rates reported among adult cohorts. Injuries as a result of incidental body contact, particularly at the knee and ankle, should be targeted for injury prevention by developing appropriate interventions. Similarly, increased bracing and falling skills, and development of hand–eye coordination, are likely to result in fewer hand, head and facial injuries among young players. These injury trends should be used to foster the development and implementation of effective injury prevention practices in junior Australian football, ultimately leading to safer sports participation for young participants.

Acknowledgments

We thank the Australian Football League Research Board, the New South Wales Sporting Injuries Committee and Sport and Recreation Victoria for project funding, and the Eastern Football League, Northside Junior Australian Football League and the Sydney Australian Football League and their associated clubs for their support and participation. CF was supported by an NHMRC Principal Research Fellowship, and BG by an NHMRC Population Health Career Development Award.

REFERENCES

Footnotes

  • Competing interests: None.

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