###### Abstract  
This study aimed to identify football players at high risk (HR) for anterior cruciate ligament (ACL) injury via a four-test battery and assess possible factors affecting classification. Ninety-one professional and semi-professional male athletes participated in a field-based pre-season screening. The cut-off points of the test battery were 10% acknowledged inter-limb asymmetry limit for quadriceps and hamstring isometric strength and single-leg triple hop for distance, in addition to the upper limit of 6 errors in the landing error scoring system (LESS). Additional assessment of hip adductors and core stability completed the global functional profile of the players. Sixty-one players were identified as HR and thirty as low-risk (LR) for ACL injury. Discriminant analysis showed that the proposed test battery classified accurately 78.0% of them, with 91.8 sensitivity and 61.9% specificity. Only four misclassified players in the LR group were at risk of inadequate treatment. All participants were considered healthy, and history of a previously rehabilitated injury did not interfere with the results. LESS seems to be the best predictor for injury-risk grouping. Prone bridge time was also a whole-body variable discriminating between groups. The proposed test battery provides a promising option for field-based pre-season ACL risk assessment of football players and needs to be studied prospectively. ACL; screening; injury risk; prevention; LESS; asymmetry; soccer +
Footnote †: journal: Applied Sciences  
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Footnote 1: email: [EMAIL_ADDRESS]  
Footnote †: journal: Applied Sciences  
Pre-seasonal assessment (PA) has been recognized as mandatory for injury prevention; however, no clear guidelines are available at the moment [16]. Recently, regarding return to sport (RTS) after ACL reconstruction, the use of a battery of tests has been proposed that evaluate knee function in order to determine safe participation in pivoting sports [17]. An efficient RTS battery should include a combination of muscle strength tests, hop tests, and measures of quality of movement [18]. The main focus of researchers for the optimal PA is to avoid costly and time-consuming laboratory testing, enabling trainers and medical teams to apply low-cost, field-based screening tests, even in low-budget teams, without compromising the training plan. PA for injury risk-profiling with portable equipment such as push dynamometers, in combination with field tests, could be useful for quick assessment of high numbers of athletes, easily repeatable throughout the season [16]. Correct biomechanics during high-impact landing is acknowledged as a key element for load management and injury prevention. Assessment of quality of movement is important to be included in PA, and the landing error scoring system (LESS) is considered a valid and reliable tool for the assessment of the athlete's landing pattern during a drop-jump task [19; 20]. Regarding strength testing, hand-held dynamometry (HHD) is an appropriate method for use in clinical and field-based settings, with moderate to good reliability and validity [21]. The criteria used to discriminate between high and low-risk athletes are subjected to ongoing research, which aims to provide objective information, easily understood and applied to support the decision-making process. For muscle strength and hop tests, a common limb symmetry index > 90% is the most common acceptable criterion [17]. For the quality of movement when using the test landing error scoring system, various cutoff scores have been suggested, with up to six errors indicating acceptable landing mechanics [20; 22; 23]. Apart from the one-dimensional open-kinetic chain tests for muscle strength, hop performance and landing technique represent a global body function, connected to core stability [24; 25; 26; 27].