# Effects of Agility Training on Skill-Related Physical Capabilities in Young Volleyball Players
## 1 Introduction  
With the advances in technology, sports are being scientifically tested and trained to enhance athletic performance, and any measurement is an assessment tool for physical exercise and science [1]. Having good explosive power and agility positively affect short sprinting or various physical activities, and the assessment of athletic performance usually includes the evaluation of straight sprinting, change-of-direction (agility), jumping, and aerobic metabolism [2, 3]. For most athletes, agility is an important athletic ability and is often the key to victory or defeat [4]. In many sports settings, athletes must react to the ball's direction, the opponent's attacking movement, or the teammate's pass by moving quickly [5], for example, by stealing bases in baseball, passing in basketball, dodging in boxing, and six-point footwork in badminton. Agility is inextricably linked to muscle strength, reaction time, speed, explosive power, and coordination [6, 7, 8], and can even be said to be a combination of these basic athletic abilities. In competitive sports, agility is often used to define the defensive ability of athletes [9], and for volleyball players, agility training can improve their defensive ability and performance in volleyball [5, 10, 11]. The defensive ability in volleyball (including serving-receiving and spiking) is the mainline of defense that prevents the opposing team from scoring on offense; if one cannot defend, one cannot disrupt the opponent's offense and one cannot build an organizational offense. According to [PERSON] et al. [12], the importance of ball handling, serving-receiving,and defense is higher for good women's volleyball teams, which is a difference between men's and women's volleyball because each round trip takes longer in women's volleyball. Previous studies indicate that elite teams are significantly better at serving and receiving than non-elite teams and that the quality of offense depends on the quality of handling, which, in turn, depends on the quality of serving-receiving or defense [13]. Thus, defense is a significant skill. Defensive techniques are highly associated with muscle strength, flexibility, coordination, and rapid reaction, and movement is effectively generated through the hip, knee, ankle, and foot muscles [14], which is related to the speed and space limitations of volleyball. In a fast and fluid game, the defender is often forced to make short and fast shifts; therefore, the faster the attack, the higher the efficiency [15; 16]. With the offensive and defensive systems, teams at different levels present varying contents. This variation relies on the maturity and stability of the athletes, and continuous adjustments in the daily training process can improve the overall performance of the team. Effective training methods help increase the player's reaction speed, which in turn shortens the overall reaction time and makes the shift speed of receiving the ball faster. However, the regular training routines are not sufficient stimulation for the improvement of agility and must be trained specifically. [PERSON] and [PERSON] [17] reported the specific adaptations needed to impose the demands' principle, 3-4 times a week, more on 1 day and less on the next. The main goal of training is to adapt the body to movement and improve agility through repetitive practice [18], which means the training variations will differ according to the length of the program, and the ability, skill, or personality of the individual. Commonly used training methods for agility include back-and-forth jumps, side jumps, multipurpose ladders for training, step hurdles, and wooden box training [19], which, for young volleyball players, are safe and effective training methods that can enhance agility, coordination, and quickness. For volleyball training, agility training is a good way for volleyball players to use their physical stamina and skills better to perform better. The subjects of this study were middle-school girls aged 12-15.