Objective of the study was to profile and analyze the ground response and bar control biomechanics for classical clean-and-jerk style in weightlifting sport. Methods and structure of the study. We used for the purposes of the study the Russian State University of Physical Education, Sport, Youth and Tourism-2012 biomechanics test system to rate the technical and speed-strength fitness of the sample. The bilateral video capturing technology registers the bar butt movement trajectory to obtain the bar mass center movement kinematics and dynamics plus its rotation versus the vertical and sagittal axes. The dynamometric test platform registers the ground response vectors to calculate the pressure center coordinates and profile the athlete-plus-weight system joint mass center travel kinematics and dynamics. We sampled for the tests junior weightlifters (n=12) from Olympic Reserve School #2 in Moscow qualified Class I to MS, with the sample being 17.2±1.9 years old, 69.9±16.1 kg heavy and 1.68±0.1 m tall on average. The athletes executed clean-and-jerk exercise in the tests with the weighs rated at 85-95% of the individual maximums i.e. 102.2±23.1 kg on average. Results and conclusions. The study analyzes the key phases of the clean-and-jerk sequence versus the competitive success rates in the new clean-and-jerk style phasing system. The analyses made it possible to find additional informative dynamic characteristics to rate the individual technical and speed-strength fitness based on the ground response force rating tests. Absolute and relative vertical ground response force vectors were found to significantly exceed the forces applied to the bar in every movement phase. Thus the maximal horizontal bar force vector at the start of the final acceleration phase was tested almost six times higher than the ground response force gradient. Most of the system acceleration power rates were tested higher than the bar acceleration power, especially in the jerk phases. In the clean (pull on the chest) phase, the bar acceleration power is approximately the same as the whole system acceleration one. The pressure center travel trajectory pattern was virtually the same in the sample, with relatively wide individual variations in the phase-specific shifts of the pressure center. The pressure center shifts were tested the largest in the preliminary acceleration and transition phases.
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