Injury characteristics in children's football and perspectives for prevention

Sport and physical activity for children is widely recommended to support a healthy lifestyle. Football is the most popular sport worldwide. Given its popularity, football is an excellent setting to fulfil sufficient physical activity levels. Football can induce considerable beneficial health effects. However, injuries may be an unfortunate consequence of participating in sport. In light of the large number of players football injuries relate to a public health issue. Therefore, the application of suitable injury prevention seems indicated. Epidemiological data are required as a basis for the development of a tailored injury prevention programme. Our topical review on football injuries in child and adolescent players revealed a clear paucity of such data relating to the youngest age groups (players under 13 years of age).
This PhD project envisaged four aims:
• to quantify the efficacy of exercise-based injury prevention programmes in child and adolescent sport in general and with respect to different characteristics of the target group, the injury prevention programme, and the outcome variables. Therefore, we conducted a systematic review with meta-analysis.
• to analyse the incidence and characteristics of football injuries in children aged 7 to 12 years in a large-scale prospective epidemiological study.
• to analyse injury risk factors based on our prospective data.
• to develop an age-specific injury prevention programme for children’s football and to test this programme regarding its feasibility and its effects on motor performance in a pilot study in 7 to 12 year old players.
Injury prevention meta-analysis
For our meta-analysis we conducted a systematic literature search in six databases and found 21 relevant studies. The original studies included a total of 27,561 athletes (median age 16.7 years; range 10.7 to 17.8). The overall injury rate ratio between intervention and control group was 0.54 (95%-confidence interval 0.45, 0.67), P < 0.001. Injury prevention programmes that included jumping/plyometric exercises showed a larger (P = 0.002) injury preventive effect than studies without such exercises.
The results provide good evidence and clearly demonstrate beneficial effects of exercise-based injury prevention in youth sports. A practically relevant overall injury reduction of 46% has been observed. Based on these findings, in particular multimodal programmes including jumping/plyometric exercises can be recommended. However, there is a considerable lack of data for children (under 14 years of age). We concluded that future research should focus on these age-groups.
Football injuries in children
We conducted a prospective epidemiological study on injuries in children’s football over two seasons in Switzerland and the Czech Republic. Exposure of players during training and match play (in hours) and injury data were reported by coaches via an internet-based registration system. Location, type, and severity of injuries were classified according to an established consensus. We calculated injury incidence rates (injuries per 1,000 hours of football exposure). An injury was defined as any physical complaint sustained during a scheduled training session or match play resulting in at least one of the following: (1) inability to complete the current match or training session, (2) absence from subsequent training sessions or matches, and/or (3) injury requiring medical attention.
We recorded 6,038 player-seasons with 395,295 hours of football exposure. The mean age of the players was 9.3 (SD 1.9) years, and 3.9% of the participants were girls. During the study period 417 injuries were reported. Most injuries (76%) were located in the lower limbs and 16% in the upper limbs. Joint and ligament injuries comprised 31%, contusions 23%, muscle and tendon injuries 19%, and fractures and bone injuries 15% of all injuries. About a quarter (24%) of all injuries led to more than 28 days of absence from sport participation and was therefore classified as “severe”. The overall injury incidence was 0.61 (95%-CI 0.53, 0.69) injuries per 1,000 hours of football exposure during training sessions and 4.57 (95%-CI 4.00, 5.23) during match play. Injury incidence rates increased with increasing age.
A comparison between the findings of our prospective study on injuries in children’s football and our topical review (that mostly included older players) showed differences in injury patterns. Children sustained a relatively high proportion of fractures and bone stress and injuries to the upper limbs. This clearly underlines the necessity of an age-specific injury prevention programme for children’s football.
Risk factors for football injuries
This project aimed at investigating risk factors for football injuries in children. We analysed time-to-injury data of our prospective epidemiological study using standard as well as extended Cox models accounting for correlations on team- and intra-person-level. We analysed injury risk in relation to age, sex, playing position, preferred foot, and with regard to age-independent body height, body mass, and BMI. Further, we analysed injury risk in relation to playing surface.
The overall injury risk was increased by 46% (P < 0.001) per year of life. Injury risk was higher in age-adjusted taller players (higher percentile-rank). Injury risk was increased on artificial turf (39%; P < 0.001) and lower during indoor sessions (32%; P < 0.001) compared to natural grass.
Age is known as a risk factor from older players and was confirmed to be a risk factor in children’s football. The playing surface has been discussed earlier as a risk factor. However, latest generation turfs did not show an increased injury risk compared to natural grass in different studies on older (mostly high-level) players. Injury risk in relation to sex should be further investigated in future studies.
Development of “FIFA 11+ Kids”
Based on the gathered knowledge, we developed a tailored injury prevention programme for children’s football called “FIFA 11+ Kids” which takes age-specific injury patterns of the youngest players into account. “FIFA 11+ Kids” is a 15-minute warm-up programme. In its first version it consisted of 7 different exercises each with 3 levels (with increasing difficulty). The programme focuses on (1) spatial orientation, anticipation, and attention especially while dual-tasking (to avoid unintended contact with players or objects) (2) neuromuscular performance, body stability, and movement coordination (to prepare the body for the physical demands of playing football and to reduce the number of falls) and (3) appropriate falling techniques (to minimise the injury risk when falling). We slightly modified “FIFA 11+ Kids” based on the practical experiences during the pilot study. The main changes were 2 additional levels for each of the 7 exercises.
“FIFA 11+ Kids” – motor performance (pilot study)
We conducted a cluster-RCT (pilot study) to evaluate the feasibility of “FIFA 11+ Kids” and to test potential effects on motor performance in 7 to 12 year old children. We were interested in effects on motor performance, as effective injury prevention programmes generally influence modifiable risk factors (e.g. lack in balance, power or strength). We stratified 12 football teams (players aged 7 to 12 years) into an intervention (N = 56 players) and a control group (N = 67). The intervention group conducted the 15-min warm-up programme “FIFA 11+ Kids” twice a week for 10 weeks. The control group followed a standard warm-up (sham treatment). During pre- and post-tests we assessed parameters to determine balance, agility, power/strength, and football-specific skill/technique of the children. We used magnitude-based inferences and linear mixed-effects models to analyse the performance test results. We observed beneficial effects favouring the intervention group in dynamic balance, agility, jumping performance, and football-specific skill/technique.
The observed improvements of motor performance indicate that “FIFA 11+ Kids” can positively influence intrinsic injury risk factors. Importantly, no negative side effects of the programme were observed. Coaches’ as well as players’ feedback regarding the feasibility of the programme were positive.
Outlook: “FIFA 11+ Kids” prevents injuries
In our subsequent large-scale cluster-RCT (that goes beyond the scope of the PhD project) “FIFA 11+ Kids” has proven to be efficacious in reducing injuries in children’s football. Considerable effects were found for overall, match, training, lower extremity, and specifically severe injuries. The observed overall injury reduction of 48% is comparable to studies in older youth football players (which we included in our meta-analysis). Based on these findings a broad implementation of “FIFA 11+ Kids” can be recommended to reduce injuries and to support the health benefits of playing football in the long term.