## 1 Introduction  
Football is the most popular sport discipline with around 200,000 professional players and 240 million amateur players. It is responsible for almost 10% of sports injuries requiring medical attention in adolescents [1; 2]. This discipline requires players to have unprecedented coordination to cope with rapidly changing external conditions. With regular practice a player acquires precision in movement and more muscle mass. Frequent training helps the player acquire the ability to execute appropriate strategic movements to effectively target his/her opponent's goal and to prevent serious injuries. To evaluate motor coordination a test was adopted many years ago to measure maximum rotation to the left and right when jumping in the air with both feet [3]. In modern training it is necessary to constantly monitor the sportsperson's coordination and balance [4; 5]. Presently there are many different methods to assess training progress, physical activity, and body postural stability, but the most important conditions in which football players should be assessed are dynamic conditions. Postural stability in athletes has been reported widely in several sports disciplines [6; 7]. That suggest that the type of sport and repetitive training may affect the balance system control. Some researchers found that football players were better that other athletes [6; 8] and that the level of playing experience influences postural control performance and adopted motor strategies [9].  
The human body's static and dynamic balance is maintained by the posture control system, which coordinates the stimuli received by the vestibular system, the visual system, and proprioceptors, and also provides a selection of optimal postural responses aimed at preventing falls [10; 11]. The posture control system tracks the position of the center of gravity (COG) over an area defined by the outline of the human feet, thus guaranteeing a stable posture [12]. The body's multi-segment construction, the height of the COG above the base of support (BOS), and a relatively small BOS, results in the human body being unstable when in an upright position. The balance control system therefore needs to constantly analyze and counterbalance all the destabilizing factors through proper stimulation of the relevant muscle groups [12; 13]. The central nervous system watches over the appropriate choice of reaction and the stimulation of the appropriate muscle reflexes. To correct posture, it adapts a movement strategy based on its analysis of linear and angular accelerations of individual body segments. Stability control of body posture depends on many factors, which includes a range of movements in the joints, muscle strength, speed and precision of movement, and the ability to perceive body positioning in space (\"body sense\") [14].  
Computerized Dynamic Posturography (CDP) allows the individual components of the human balance system to be evaluated. During CDP, signals from appropriate senses involved in maintaining balance are evaluated. The postural response time and the reaction time to unexpected support platform changes, with an appropriate motor response, is also determined as well as the efficiency of adaptive mechanisms [15]. CDP is the gold standard to differentiate between sensory, motor, and central adaptive impairments to postural control [16]. In football it can be an opportunity to track the rehabilitation of postural control impairment after anterior cruciate ligament injury, which is one of the most common in this sport [17].  
The aim of this study was to compare the behavior of the balance system between two groups of young women and to determine the effect of regular practice. One group consisted of young female footballers who train regularly and the other, a group of peers who do not participate in any regular sporting activity. We hypothesize that football players would show better postural balance performance.