TAKE-OFF STRUCTURE AND TOUCH DOWN LOADS DURING LANDING IN SELECTED RHYTHMIC SPORT GYMNASTICS JUMPS
Keywords: rhythmic sport gymnastics, jumps, landing, load, co-ordination
AbstractINTRODUCTION: Jumps can be found in various sport disciplines, and the technique of execution depends on the specifics of the event. In the case of rhythmic sport gymnastics, jumps as well as turns, elements of flexibility and balance in connection with the use of equipment are some of the elements assessed in competition. Each jump must have a form defined in the rules. A long flight phase makes possible the execution of the desired form of a jump. Rhythmic sport gymnastics is one of the sports disciplines with early specialization, which means that girls start training when they are five years old. The specific character of this discipline consists in repeating elements of technique, which means that dozens of jumps are done landing on one or two legs during each training session. Counting the number of repetitions, the number of practice sessions in a week and multiplying by the number of weeks in the year - in the case of the youngest girls - we get about six thousand repetitions. Cumulating loads while landing and the specific structures of children’s bones are the cause of repetitive strain injury, especially to the knee and ankle joints. Research on the structure of take-offs in jumps is referred to for factors that contribute to achieving maximum length and height of jump (Aura & Viitasalo, 1989; Dowling & Vamos, 1993; Janiak, Eliasz & Gajewski, 1997), but few works deal with the landing phase and the resulting loads on the movement system. Investigations point to the importance of co-ordination, specifically of the movement of the upper extremities in the take-off phase, which may depend on the synchronization of the movements of the lower and upper extremities and trunk (Aragon-Vargas & Gross, 1997). Some authors have found that the arm swing improved the jump height (Shetty & Etnyre, 1989), increased the downward load on the legs (Amin & Bober, 1989), and enhanced the impulse generated by the lower extremities by lengthening the time of force application (Harman et al.,1990). However, in the cited papers the authors did not consider the influence of arm swinging on load parameters during the landing phase. The aim of this paper is to define the value of the reaction force which must be absorbed during the landing phase and to investigate the share of the upper extremities in damping touch down loads in jumps with different difficulty levels.
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