Copyright © 2019 by the Józef Piłsudski University of Physical Education in Warsaw, Faculty of Physical Education and Sport in Biała Podlaska Pol. J. Sport Tourism 2019, 26(1), 3-7 DOI: 10.2478/pjst-2019-0001 3 Introduction In rhythmic gymnastics, postural control is trained daily. The determinants of efective training in this sports discipline were investigated by Bobo-Arce and Mendez-Rial [1], according to whom an important component of this process is the devel- opment of postural control abilities during the performance of single-leg exercises, which may be carried out on the whole foot or on the toes (in relevé). Most exercises in rhythmic gymnas- tics require an above-average ability to maintain balance while standing on a very small support surface; what causes addition- al difculty is that the gymnast is required to keep the free leg in diferent demanding positions and move the apparatus [2]. Since the beginning of their sport training, which starts at the age of 5-6 years and takes from 2 to 3 hours a day, rhythmic gymnasts learn how to perform gymnastics exercises, most of which require improving the ability to maintain a vertical po- sition of the body [3, 4]. Balance exercises in which gymnasts stand on the toes of one leg with the other leg raised in a split and held with the hand in the head area, which are characteris- tic for rhythmic gymnastics, can be considered an extreme form of postural balance tasks. This position of the raised leg causes additional lateral movements in the hip joint of the supporting leg, which are signifcantly limited in double-leg positions [5]. In rhythmic gymnastics, the greatest technical value is at- tributed to balances which are performed in relevé [2]. The con- dition for maintaining balance on such a small support area is minimising the movements of all body segments in such a way that the vertical projection of the centre of mass (COM) falls within the surface of the sole of the foot of the supporting leg (which is a general prerequisite for maintaining a vertical posi- tion) [6]. The gymnast must block all degrees of freedom in the musculoskeletal system in order to maintain balance on such a small support surface. In these positions, stabilisation of the ankle joint, which is regulated by the m. gastrocnemius, is par- ticularly important [7, 8]. Many balance exercises are performed in routines with ap- paratuses both by gymnasts starting their sporting careers and elite gymnasts. Gautier et al. [9] have found that gymnastics training activates specifc adaptive abilities, which may manifest themselves in better postural control in difcult vertical posi- tions of the body [10, 11]. One parameter describing the quality of postural control is the range of centre of pressure (COP) displacement. The values of this parameter in the anterior-posterior and medial-lateral POSTURAL CONTROL IN FEMALE RHYTHMIC GYMNASTS IN SELECTED BALANCE EXERCISES: A STUDY OF TWO CASES MAŁGORZATA SOBERA 1 , ALICJA RUTKOWSKA-KUCHARSKA 2 University School of Physical Education in Wroclaw, Faculty of Physical Education, Department of Gymnastics 1 , Department of Biomechanics 2 , Wrocław, Poland Mailing address: Alicja Rutkowska-Kucharska, University School of Physical Education in Wroclaw, Department of Biomechanics, 35 Paderewskiego Avenue, 51-612 Wrocław, tel.: +48 71 3473395, fax: +48 71 3473181, e-mail: alicja.rutkowska-kucharska@awf.wroc.pl Abstract Introduction. The aim of the study was to determine the diferences in the quality of postural control between two female rhythmic gymnasts with diferent training experience during the performance of balance exercises. In rhythmic gymnastics, the same balance exercises are performed by novice and elite gymnasts. Balance exercises involving standing on the toes of one leg with the free leg raised in diferent positions are considered to be extreme forms of exercise in terms of the postural balance abilities required. In coaching practice, it is important to have tools which facilitate the objective assessment of the process of maintaining balance in such exercises. Material and methods. The study involved two female rhythmic gymnasts: a younger one (age = 8 years and training experience = 4 years) and an older one (age = 21 years and training experience = 14 years). The athletes performed three balance exercises standing on a Kistler platform: the split with hand support (lateral balance), the ring with hand support, and the back split without hand support (balance on the whole foot). The parameters describing the quality of postural control used in the current analysis were the range and velocity of COP displacements in the anterior-posterior and medial-lateral directions. Results. Postural control in the balance exercises in the younger rhythmic gymnast was characterised by almost two times greater COP displacements in the anterior-posterior direction and more rapid than that of the older gym- nast. COP displacements in the medial-lateral direction in all the exercises described did not diferentiate the subjects. In the back split without hand support, the older athlete showed greater variability of postural control with smaller COP displacement and velocity than the younger gymnast. Conclusion. Gymnastics training should include exercises strengthening the muscles acting on the ankle and hip joints, which could improve the stability of these joints during the performance of difcult balance exercises. Improving the stabilising function of these muscles helps to minimise anterior-posterior movements in these joints. Key words: single-leg stance, COP trajectory, training experience Original research papers