# Evolution of Core Stability, Athletic Performance, and ACL Injury Risk across a Soccer Season
###### Abstract  
Soccer athletic performance varies across a soccer season due to training and fatigue. In addition, it is known that core stability is linked with anterior cruciate ligament (ACL) injury risk but their variations over a season are unknown. The aim of the study was to determine the evolution of core stability, athletic performance, and ACL injury risk among young high-level soccer players at four key moments of a season: pre-season (PRE), start of season (START), mid-season (MID), and the end of the season (END). Core stability scores increased until mid-season, while ACL injury risk scores (measured during sidestep cuttings and single-leg landing) decreased thanks to an injury prevention program between START and MID. These results are in line with the literature, which demonstrates that a high level of core stability is linked to a low injury risk. Evolution of athletic performance was not consistent throughout the season, being dependent on the specific phases of training performed by the athletes. Therefore, assessing core stability, athletic performance, and ACL injury risk multiple times across a soccer season could help coaches to adapt their training programs properly.  
trunk control; longitudinal study; field testing; training; soccer +
Footnote †: journal: Medical  
stability exercises) have successfully helped to reduce ACL injury for male and female soccer players [20; 21; 22]. The impact of core stability on soccer performance has also been demonstrated in the literature, as core stability training has been associated with improved shooting speed [23], sprinting time [23], cutting time [24], and jump performance [25; 26; 27] in soccer.  
Meanwhile, these physical parameters evolve during the competitive season in various sports (e.g., handball, softball, or soccer) [25; 28; 29; 30; 31]. For instance, it has been reported that during the pre-season period, soccer players mainly train using low-intensity aerobic exercises to develop endurance capacity, with force and speed exercises to improve sprint and jump capacities [25; 29; 30; 31]. Then, soccer players raise their athletic level throughout midesaon, as evidenced by improvements in jump height, sprint times, and agility level [25; 29; 30; 31]. Finally, in the second part of the season, semiprofessional soccer players are used to maintaining their athletic level, e.g., countermovement jump height, 15 m sprinting, and Illinois testing [25], after reducing high-intensity training and focusing on aerobic at low intensity in order to prevent fatigue. However, the evolution of the estimated ACL injury risk and core stability throughout the season is still unknown. Thus, investigating core stability evolution in comparison with performance and ACL injury risk over a full soccer season could bring new insights on the effect of regular training on these major aspects of soccer practice and lead to better physical and sport-specific conditioning programs and evaluation recommendations. Therefore, the aims of this study were (i) to understand the evolution of core stability, performance, and ACL injury risk across a soccer season and (ii) to determine the relationship between the evolution of core stability, performance, and ACL injury risk, respectively. Firstly, we hypothesized that core stability and performance would evolve in the same way and in opposition to ACL injury risk factors. Secondly, we hypothesized a positive correlation between the evolution of core stability and performance and a negative correlation between core stability and ACL injury risk factors.