Considering that in the present study tried to describe the characteristics of static, dynamic and perceptive body balance in professional league youth soccer players from the city of Manizales - Colombia, through dynamic and static balance tests and the CAIT questionnaire, the respective discussion is presented below.
Static Balance (Static Stabilometry; Eyes Open and Eyes Closed)
For the soccer player during the development of the game, postural balance is required to maintain stability during the game and develop their different motor gestures (Olsen, Myklebust, Engebretsen, Holme, & Bahr, 2005), becoming a relevant skill to reduce risk of injury and its relapse (Gonell, Romero, & Soler, 2015). Accordingly, the ability to maintain postural stability and balance is based on multiple synergies of proprioceptive and exteroceptive messages, mediated by the articular system, where they are combined according to Freeman & Wyke (1966) with capsules and ligaments that coordinate all the systematic response; in which three modes of postural coordination have been found, the first was rest position coordination, identified as the ankle strategy, where the postural system is due to 3 neuromechanical elements with their interrelationships that include passive mechanical systems or non-contractile structures, and passive muscle tension that maintains stability against disturbances imposed by influences of passive stiffness, joint laxity, and range of motion; the active (or muscular), contractile elements that cross the ankle and provide control tension for the ankle, and finally, the neural, which influences postural stability (You, Granata, & Bunker, 2004). Also, there is the hip strategy, where hip movement regulates postural stability, and finally, the integrated hip-balance coordination strategy (Tropp, Odenrick, & Gillquist, 1985).
Likewise, Nashner (1971) proposed that, under normal conditions, the ankle joint provides a greater condition for the stabilization of body balance, constantly feeding back vestibular information complemented by other sensory-perceptual data.
However, under abnormal conditions, if injuries occur at the ankle level, the proprioceptive response tends to be altered, affecting not only the joint component, but also the muscular response, causing the symptoms of pain at the ankle and foot level and therefore, the appearance of functional instability (Freeman and Wyke, 1996); situation analyzed in the study carried out by Tropp et al., (1984), where soccer players with balance problems presented a four times greater risk than those who did not have alteration, measured on a baropodometric platform at 60 seconds, similar to the findings made by Watson, (1999). Conversely, the stabilometric results developed in the group of soccer players in this study did not show significant changes between the results of the tests with EO and EC. This indicates that there are no significant variations between body balance due to the elimination of a sensory system and there are no vestibular impairments, possibly because, when these players were evaluated, they did not present persistent functional instability, in the case of those who were affected by ankle sprain sequelae, and/or their regular training, which could increase the postural balance (Gribble, Hertel, & Plisky, 2012; González, et al., 2011).
Dynamic Balance (Limits of stability)
According to the results, it was related to the laterality of the soccer players. Accordingly, soccer players are expected to develop greater stability in the dominant segment, because the different positions on the playfield must ensure effectiveness and their bilateral foot coordination to develop the different passes to teammates or the goal as an objective proposed in the structure of the game: For this, the inclusion of specific exercises in coordination, static and dynamic balance and on different surfaces, stimulate the activation and conditioning of somatosensory, vestibular and visual systems, fundamental in postural control during the execution of the different motor gestures of the soccer player (Owoeye, Palacios & Emery, 2018).
In Junge & Dvorak (2004) and Bernal & Domínguez (2016) results, similar to the ones from the present study, indicated that the asymmetry in percentages of the center of gravity, as well as support surfaces, had a considerable impact on overuse injuries, associating the asymmetries to causes of dominance of lower extremity laterality and, in sports such as soccer, different gestures and feints, as well as kicking the ball, accentuate significant shortening of one lower limb compared to the other. From another point of view, lateral imbalance can also be related to an anatomical shortening of the femur or tibia on one side, or to a functional postural disorder of the feet. According to Gagey & Weber (2001), shortening of the lower limb is due to bilateral asymmetric calcaneal varus or bilateral asymmetric calcaneal valgus.
It should be noted that, during football practice and matches, passes and kicks are the most used game techniques, preferably with the dominant leg, while the non-dominant leg is used as a support limb, which could explain in the same way, why the left foot in the present study presents greater stability, and this can be due to the postural control generated on the lower limb that performs the support in relation to the leg that makes the kicking gesture, requiring greater postural control. This limb difference in single leg balance performance may be further enhanced based on football experience, i.e., years of soccer training, whereby postural control requires mastery of the body in space for the purposes of stability and orientation (McCann, Kosik, & Beard, 2015 ).
In this study, a significant decrease in anteroposterior oscillations with EC is observed compared to oscillations registered with EO, evidencing better vestibular and motor control during dynamic activities; since the vestibular, visual and proprioceptive system inform higher nervous centers, the changes in the position of the soccer player in relation to the playfield, registering position variations in the different body segments so that the soccer player performs compensatory reflex movements to maintain the position or make dynamic adaptations that favor the optimal execution of the sporting gesture. In this sense, the sensory systems in question modulate and allow to guide movements to maintain posture, balance, eye movement, displacement of the different segments of upper and lower limbs, through control of the motor system of the brain and spinal cord (Ortíz Corredor, Rincón & Mendoza, 2016).
Furthermore, the soccer player uses the ankle movement as a strategy to maintain balance within the base of support, generating displacements in an anteroposterior direction, which excursion will be greater or less depending on the movement of the center of gravity, how much moves away from the limits of stability, and in the case of the present study, the soccer players, as compensation for closing the visual system, make postural adjustments to maintain their stability by reducing the amplitude of the oscillations with their eyes closed. This being an adequate response from the study participants, since what is expected is that an individual without balance-related health conditions uses the ankle strategy during support on stable surfaces (De Moya, Baydal, & Vivas, 2005).
However, to the extent that this surface generates some instability or becomes less stable, the soccer player may tend to include the hip during his movement, in which the hip joint is used more, generating medial-lateral movements, where the center of gravity moves faster and moves closer to the limits of stability; as observed in the present study, since a greater mediolateral instability was found with respect to the anterior-posterior instability, identified with a greater number of oscillations during movements in this area and an even lower range of oscillation given by the amplitude of the sway (Gianoli, McWilliams, Soileau, & Belafsky, 2000).
According to the above, the perception of instability influences the appearance of functional insufficiency, but this aspect is controversial in terms of its assessment (Guzmán-Muñoz, Gatica-Rojas, & Méndez-Rebolledo, 2014). Possibly, it is due to the fact that the traditional clinical evaluation requires great skill, but currently, there are self-reported questionnaires, which have been used in order to identify symptoms and functional limitations such as those of the talocrural joint (Fujii, Luo, Kitaoka, & An, 2000).
In the case of the present study, it was observed that the sum of the scores of the CAIT test of the right and left feet did not present significant differences, which indicates that, in both feet, the group was not significantly different and when observing the anteroposterior oscillations with EC, a statistically significant decrease is observed compared to what was observed in the test with EO, which shows better vestibular and motor control during dynamic activities influencing the vestibular and visual system (Cisneros Perdomo, Sánchez Castillo, Hernández Chisholm, & Calzadilla Galainena, 2014). But there is greater medial-lateral instability with respect to the anteroposterior position, identified by the greater number of oscillations during movements in that area and a smaller range of oscillation given by the oscillation amplitude. It could be indicated according to what was recorded in this type of instrument, that they do not reach to indicate functional instabilities (Rozzi, Lephart, Sterner, & Kuligowski, 1999), though others affirm that athletes assessed with this type of questionnaire identify early potential affectations associated with the deficit in postural control that affects their stability (Wikstrom, Naik, Lodha, & Cauraugh, 2009) (McKeon & Hertel, 2008).