Balance control near to the limit of stability in young soccer players

Abstract

Introduction. To compare postural performance and strategies in young soccer players between quiet standing and standing close to the limits of stability. Methods. The study included sixteen boys aged 13 years, who have trained soccer for about 5 years. Their body balance was assessed using the Kistler force platform. All participants performed 6 trials, lasting 20 seconds each: three with eyes open and three with eyes closed. The trials included quiet stance, the maximum foreward tilt and maximum backward tilt. Based on the center of pressure (CoP) recorded at sampling rate of 100 Hz the following sway parameters were evaluated: variability, range and mean velocity as well frequency, entropy and fractal dimension. Results. in frontal and sagittal plane, the CoP variability, range and velocity during stances near the limits of stability were higher than in quiet stance. These increases were independent of the direction of body tilt. Body tilts decreased entropy and frequency in the frontal plane and increased fractality in the sagittal plane regardless the tilting direction. There was also a decrease in fractality in the frontal plane that took place during forward tilt only. Conclusions. Forward and backward tilt deteriorated postural performance in a similar way. However their effects on postural strategies were direction dependent. The strategies in the frontal plane indicated increased investment of attention, lower automaticity and more stable control. in contrast, the sagittal strategies displayed decreased stability with no changes in automaticity. Such inter-plane differences suggest specific allocation of the critical postural tasks in response to the threat of fall. it is plausible that, due to complexity of these reciprocal relationships, testing postural control near to stability limits may better differentiate specific groups and experimental manipulations than testing the limits of stability only.