Postural control in girls practicing volleyball is different than in non-playing peers: comparison of data on the center of pressure and ground reaction forces

A comprehensive explanation of the relationship between postural control and athletic performance requires evaluating body balance in athletes of different performance levels. To fill this gap in relation to volleyball, the aim of this study was to compare the balance of intermediate adolescent female players (VOL, n=61) with inactive peers (CON, n=57). The participants were investigated in normal quiet stance during 30 s trials on a Kistler force plate. The traditional spatial (amplitude and mean speed) and temporal (frequency, fractality and entropy) indices were computed for ground reaction forces (GRF) and center-of-pressure (COP) time-series. The spatial parameters of the both time-series did not discriminate the two groups. However, the temporal GRF parameters revealed much lower values in VOL than in CON (p<.0001). This leads to three important conclusions regarding posturography applications. First, GRF and COP provide different information regarding postural control. Second, measures based on GRF are more sensitive to changes in balance (at least those related to volleyball training and perhaps to similar training and sports activity regimens). And third, the indicators calculated on the basis of these two time series can complement each other and thus enrich the insight into the relationship between balance and sports performance level.