Changes in the Level of Dynamic Balance Among Winter Sports Competitors, Candidates for ZSMS (School of Winter Sports Championship) in Zakopane over the Years 2007-2016

Research aim. The aim of the study is to determine changes in the level of the ability to maintain balance in dynamic conditions over the last decade among winter sports competitors, candidates for junior high and high school of the Winter Sports Championship School Complex in Zakopane (ZSMS). The following research questions were formulated: 1. Have there been any significant changes in the level of dynamic balance among candidates for practicing winter sports at ZSMS Zakopane over the last 10 years? 2. Did the possible changes in the examined subjects have a similar range in both the analysed directions of deflection (anterior-posterior and lateral)? 3. Have the differences in the level of dynamic balance between 13 and 16-year-old candidates remained at a similar level in the analysed time period? Materials and methods. The study comprised a group of 133 boys, candidates for junior high school (age 13.32 ± 0.77), and a group of 198 candidates for high school (age 16.02 ± 0.48). The Libra balance platform from the Italian company EasyTech was used to determine the level of balance on unstable an unstable surface. A sinusoid with an amplitude of 5° and a frequency of 10 cycles /min were used as the trajectory pattern. The balance curvature of r = 40 cm and the 6th degree of difficulty (5° deviation from the reference line in each direction) were used. The results of the following trials were used for the analysis: stability index (SI), total area (TA) and index of balancing precision (IBP). The tests were carried out separately in the frontal and sagittal planes. Before beginning measurements, basic somatic features of the subjects were evaluated. The differences in the results of individual stability parameters were verified via the Kruskal-Wallis and U Mann-Whitney tests. Results. Over the analysed decade, both the 13- and 16-year-olds demonstrated significant improvement in the values of all tested stability parameters in the frontal plane. Among junior high school students, values amounted to: SI = 40.5%; TA = 30.0%; IBP = 52.5%, while for high school students: SI = 32.1%; TA = 23.6.0%; IBP = 49.4%. However, the occurrence of such positive changes in the sagittal plane was not confirmed. Similarly, 13-year-olds showed improvement for the results in the following areas: SI = 22.9%; TA = 18.2%; IBP = 33.5%, while 16-year-olds: SI = 11.6%; TA = 9.9%; IBP = 16.8%. A gradual disappearance of the differences in the balance level between junior high and high