Introduction
The risk of injury in a professional football player has been estimated to be 1000 times higher than for typical industrial occupations generally regarded as high-risk,1 with the most frequent injuries occurring in the lower limbs.2 As lower limb injuries are so common, prevention of these injuries is important when considering personal grief, disabling consequences and the high cost due of injuries3 in terms of treatment and absence from competitive play.
Professional footballers suffer 710 injuries per 100 000 hours of training/match time, while 47% of players retire due to an injury-related problem.4
Teams that avoid injures tend to achieve better final league standings.5 A professional football club can expect around 50 injuries resulting in time lost from play each season.6 Both injury prevention strategies and rehabilitation after injury are complex, requiring specialist knowledge and experience of professional coaches and trainers.7
Though the effects of mobility, proprioception, strength asymmetry and Functional Movement Score (anthropometric variables) on injury have been studied previously, no study to date has incorporated all of these variables.
It has previously been found that mobility is related to injury in male athletes and that preseason mobility programmes could reduce injuries.8 These studies suggest that preseason and day-to-day mobility training could be beneficial in preventing injury. Modifications in flexibility training protocols have been found to reduce hamstring injuries in professional footballers,9 though the findings of this study were not fully conclusive due to variations in training patterns and not all clubs returning their survey. There has been some support that general joint laxity is predictive of leg injuries.3
Proprioception is defined as the sense of body motion—the ability to feel the body moving in space.10 It has been shown that an implementation of a proprioceptive-coordinative training programme increased all measured fitness indicators and resulted in a reduced injury incidence by 400%.11
The effectiveness of neuromuscular training in reducing the rate of knee injuries has also been evaluated:12 a 15 min neuromuscular warm-up programme reduced the overall rate of anterior cruciate ligament (ACL) injury in adolescent female football players by 64%.
The effect of knee injury primary prevention programmes on ACL injury in female athletes in various sports has proven to be effective.13 This study found a 70% decrease in non-contact ACL injuries in the intervention group versus control group, attributable to prepractice warm-up type training protocols.
Strength asymmetry is considered a musculoskeletal abnormality, defined as a bilateral strength imbalance.14 It is important to understand that skills in football are unilateral and consist of patterns of asymmetrical movement15 as the majority of football players favour either their left or right leg, and that it is this preference that may cause asymmetry in strength in the lower limb.14
As the strength asymmetry score indicates differences in exerted force on an isometric hold, the lower the asymmetry scores the more balanced a player is, in terms of the left and right limb exerting equal force.
Strength asymmetry has previously been proposed as a possible identifier of injury risk16 and has been found to be negatively associated with injury in the lower extremities.7
Functional Movement Screen (FMS) is a seven-item (deep squat, hurdle step, in-line lunge, shoulder mobility, active straight-leg raise, trunk stability push-up and rotary stability) screen that assesses basic movement patterns17 and an athlete's mobility and stability. FMS was developed as a functional movement and dynamic balance assessment to capture the complex construct of motor control. Each item is scored from 0 to 3 for a total possible sum score of 21 points. Higher scores represent better functional movement.18 For this study, a modified version of FMS (mFMS) was used which better reflected the basic lower limb movement patterns, mobility and stability of a professional footballer.
Preparticipation data can be used to identify those whom may be at risk of injury. It can also be used to discover talent, advance skills and provide baseline data for return to sport after injury and to develop a profile which reflects the characteristics held by those participating in the sport.18–21
Currently functional movement tests and in particular the FMS as a screening tool is commonly used in sport.22 However, there is little conclusive evidence supporting the reliability and validity of the FMS. Furthermore, there is a lack of evidence to support the inclusion of the functional movement tests selected for the FMS and their relevance to screening tools for specific client groups.
Assessing basic fundamental movements through a more functional approach has the potential to focus on modifying sporting movement patterns rather than just concentrating on specific muscles or joints,20 ,23 further support this by suggesting performance tests need to be designed to closely replicate the players' normal activities. In particular for football, this means including flexibility, movement patterns of main joints, specific football skills, power, speed and endurance.20 ,24 Specific testing programmes should identify a player's physical profile revealing their strengths and weaknesses and thereby their injury susceptibility.25
FMS score has previously been shown to predict injury risk, even outside of a sporting setting26 and standardised intervention programmes have been shown to improve FMS scores.27
Studies have explicitly shown that players with low scores on the FMS scoring system were more likely to be injured than those with high scores.28
The aim of this study was to determine if mobility, proprioception, strength asymmetry and mFMS could be used as predictors of lower limb injury in professional footballers.