DYNAMICAL FACTORS RELATED TO VERTICAL JUMP PERFOMANCE
AbstractINTRODUCTION - In most of sport exercises, the displacement of body Center of Mass (CM) is an important factor to de-terminate performance. And greater the velocity at takeoff phase, greater the height achieved by the body CM. High jumps are influenced by the net combination of different joints moments and its synchronization during this task. Thus, also the countermovement may influence high jump performance (HOCHMUTH & MARHOLD, 1978). To measure the effectiveness of training into increasing the height in vertical jump relays information to both coach and athlete in manner to adapt the training. The purpose of this study is to analyze temporal and frequencies factors of ground reaction force GRF and the effect of limitation of arms swing and trunk extension in vertical jump. METHODS AND EQUIPMENT - All the exercises were performed on a strain gauges force platform. The ground reaction force (GRF) had been sampled at 800 Hz frequency and after the determination of its frequency components by the use of FFT, the raw signals were low-pass filtered at 160 Hz. A video camera was exerted to control the set of jumps. The volunteer subject for this study was a male high jumper, 26 years old, 70.4f0.5 kg weight, 184.0k0.5 cm tall. Four different types of vertical jumps were performed (set of 5 trials) and analyzed in this study: 1) standard vertical jump; 2) jump with- out the elevation of upper limbs; 3) jump without the extension of trunk; and 4) jump without both the elevation of upper limbs and extension of trunk. All that jumps were preceded by countermovement. RESULTS AND DISCUSSION - Although four different techniques had been per- formed for high jumps, the temporal factors (DOWLINH & VAMOS, 1993) did not differ statistically (duration of major positive impulse and duration of major negative impulse). Eccentric and concentric phases was not different statistically. Power spectral analysis has showed that trunk mobility might be more influent than upper limb swing in the dynamic4 characteristics of the analyzed movement. Informations provided by spectral analysis probably relays important data to identify the influence of different body segments in vertical jump. It was not confirmed that the maintenance of a steady state just before the maximum vertical GRF or reducing the depression between the two positive peaks is related to the acceleration caused by arms swing. On the other hand, our results indicate that the first positive peak is probably exerted by trunk extension. In spite of the limitation of trunk and upper limb mobility, it is clear that is not possible to exclude their influence in total body moment of inertia. CONCLUSION - According to our results, despite different jumping exercises, restrictions to joints mobility changes the maxi- mum vertical GRF. Besides, tests that intend to measure the performance in high jumps according the use or not of parts of the human body may be reconsidered. REFERENCES Hochmuth G.; Marhold G. (1983) In Asmussen E. Jagenssen K. Biomechanics VI B. Dowling J.J.; Vamos L. (1 9933 J. Applied. Biornech. 9, 95-110.
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