Ziel

This study was designed to assess the effectiveness of a newly developed prevention programme (FIFA 11+ Kids), particularly tailored for the youngest players (7 to 12 years old), in reducing the rate of football injuries.

Planung

The study was designed as a two-armed cluster-randomized controlled trial (level of evidence 1) according to the CONSORT statement guidelines. It was conducted as a large-scale multi-centre study in four countries (Switzerland, Germany, Netherlands, Czech Republic). With regard to injury characteristics and football exposure we followed established guidelines for football injury research. An injury was defined as any physical complaint sustained by a child during a scheduled training session or match play resulting in (a) the inability to complete the current match or training session, (b) the absence from subsequent training sessions or matches and/or (c) the injury requiring medical attention.
Observation period: One complete football season was observed. A typical youth football season in the participating countries lasts from late summer (August or September) to early summer the next year (June or July). This corresponds to a single school year, typically with breaks (no training and match play) during school holidays.
Study population and recruitment: 7 to 12 years old children (boys and girls, born 2002 to 2007) participating in regular training and match play in an officially registered football club in Switzerland, Germany, the Netherlands and the Czech Republic were recruited. The selected age categories play on small pitches from 5 vs. 5 to 9 vs. 9. Boys and girls are not separated in these age categories. Recruitment of clubs took place via the national and regional football associations. Inclusion criteria were: the clubs must be officially registered in the regional football association, children must be between 7 and 12 years old at the start of the study and regular training must take place at least twice per week. Teams were excluded, if the coaches already performed a structured warm-up focusing on neuromuscular control or an existing injury prevention programme. Randomization All participating clubs were randomized into an intervention or a control group. All teams of the same club were randomized in the same group (clustered allocation with the club serving as cluster). Computer-generated cluster randomization was conducted by one researcher who had no direct contact to the clubs or team officials and who was not involved in the intervention. Age group, country and number of participating teams per club will serve as strata for randomization. Intervention The intervention and follow-up period lasted a full season. The preventive program was implemented at the beginning of a usual training session and replaced the traditional warm-up. The programme was implemented by the coaches at the start of at least two weekly training sessions. The prevention programme contains seven exercises and lasts about 10 to 15 min after familiarisation. The first three exercises focus on unilateral, dynamic stability of the lower extremities (hopping, jumping and landing). Further, three exercises emphasize whole body and trunk stability. The last exercise contains rolling movements to improve fall technique. The difficulty of each exercise can be progressively increased in three steps. Players started at the level of difficulty which corresponds to their current performance level. They proceeded to the next level when they performed the exercises with good control. The coaches of the control group received the instruction to regularly perform a common warm-up consisting of running and ball-based exercises (sham treatment, no neuromuscular and stability exercises). All control teams were provided with the same instructions to the prevention program after the study has been finished. Statistics and sample size estimation The primary outcome in this study was the overall injury rate. Secondary outcomes were the rate of severe injuries (> 4 weeks of absence from training and/or match play) as well as of acute joint and ligament injuries of the lower extremities. All statistical analyses were performed as intention-to-treat analysis. Time-to-injury data were analysed using extended Cox models. The models contained mixed (random and fixed) effects while assuming a Gaussian distribution for the random effects. These models account for clustering effects on team level and allow to analyse multiple injuries of players while accounting for potential correlations on intra-person-level. We estimated sample size based on data from our own epidemiological study on injuries in children´s football. In the first year we documented 218 injuries per 2522 player-years, corresponding to a yearly incidence of 8.6% injured players. A risk reduction of one third has been recently acknowledged as a relevant effect size for the difference between injuries on grass and artificial turf. Thus, a comparable effect, corresponding to a reduction of the yearly incidence to 5.8% injured players, will be considered relevant in this study. In order to achieve a statistical power of 80% and assuming an allocation ratio of 1:1 for the intervention and the control group, respectively, as well as a cluster-inflation factor of 1.7 (based on intra-cluster-correlation data from another study), about 4´000 players (2´000 players per group) were needed for statistical analysis. Finally, 3895 players remained for analyses.

(Zwischen)Ergebnisse

Erste Ergebnisse zeigen eine deutliche Verletzungsreduktion durch das Aufwärmprogramm von insgesamt rund 50%.