# Biomechanical Characteristics for Identifying the Cutting Direction of Professional Soccer Players
## 1 Introduction  
Soccer biomechanical analysis includes instep shots [1, 2], side-foot kicking [3], and curveball kicks [4], which have been widely investigated in related studies. Soccer is a group confrontation sport. Players need both attack skills and defensive ability. If the attack and defense skills and the interaction between the two sides of the attack and defense can be quantified, the competition can be mastered more comprehensively [5]. The actions in a competition are categorized into attack, defense, switching from attack to defense, and switching from defense to attack. The first task of the attacker with the ball is to score and breakthrough; that of the defender is to challenge for the ball, block or delay, and try to switch from defense to attack. There is a lot of information processing and decision-making in the movement processes between the attacker and defender. The attacker and defender form a closed system, in which the elements affect each other and are in balance when the two are in confrontation [6]. In this mode, the attacker cannot breakthrough easily, and the defender cannot steal the ball easily. In a balanced state, the defender can delay and wait for teammate support. When the defender adds pressure, the distance between the attacker and defender will change. At this point, the attacker may choose to pass the ball, cut, protect the ball, or re-establish balance. When under pressure, the reaction time and space will be limited, and the mode of attack may also change [7]. Therefore, if the defender can understandthe favorable position distance, the defender can affect the attack mode of the attacker. In this linked system, there is stable symmetry and destabilization between attack and defense situations. If the defender can understand the influence of distance on the attacker, the defender can affect the attacker's action through the defense distance. Further understanding of the kinematic characteristics of the human body in the cutting direction can reduce the possibility of a breakthrough. [PERSON], [PERSON], and [PERSON] [8] proposed a theory of the coordination view. When a player is dexterous with their motor skills, the body can increase the degree of freedom and range of motion of the joints to improve athletic performance. When describing the cutting action in different directions from this point of view, the body should be able to use relatively large body movements and the full range of motion of the joints to cut in the direction in which the player is customary Related studies have found that the foot version angle is relatively large when cutting in the customary direction [9]. There is a significant change in the knee joint angle during the initial landing period of the cutting action [10]. Previous research on the defenders' visual search strategy found that excellent players pay attention to their opponents' hip and knee areas. Therefore, the hip and knee may be the main areas used to predict the ball handler's attack action [11]. The application of distance perception enables players to master the attack and defense positions. In the attack and defense system, whether one party breaking the distance balance is also an opportunity for the other party, whether the balance can be rebuilt after breaking, and whether the distance between the attacker and defender and the time of confrontation after the balance is broken will influence factors that are yet to be investigated. The distance perception between the attacker and defender can be trained. If the action taken by the attacker can be further predicted and applied during competition, it can help the player control the rhythm of the competition [12]. Previous studies seldom used the biomechanics method to identify the cutting direction or intention in soccer games. Therefore, to better understand the movement of attackers from two different cutting directions, this study measured the differences of biomechanical characteristics, which can be applied to identify the cutting direction.