Dynamic research on diving athlete's person-board coupling when the off beat takes off
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    Abstract:

    Objective To study diving athlete's pedaling force with its function changes when getting person-board coupling with both feet gathering to press the springboard. Methods To obtain the kinematics parameters by using theoretical analysis method with material mechanics' bending stress, vibrating dynamics research technique. Results1. Deflection equation of springboard's line is δ0=y板(1)=P/6E1[-ι3+3ι3+(a2-4ιa)ι+ιa2]=ι(ι-a)2/3E1P 2. The impact stressreceived by springboard is Pd=K(P/K+(P2/K2+2ph/K)1/2) 3. The person-board coupling's natural timing frequency is ω合=(k/(m+■))1/2=((3El/(m+■)ι(l-a)2)1/2)4. Under the similar outside force, with the pivot approaching the springboard fixedend, the vertical displacement of the front end increases; with the pivot moving ahead(approach board point), the board rigidity increases correspondingly. 5. The nearer the pivot to the springboard fixed end, the bigger the board frequency will be, With the pivot moves to the board point, the board frequency reduces, while the board rigidity increases correspondingly. And if the pivot position remains unchanged, the nearer the springboard position approaches front end, the bigger the vertical displacement of the front end will be. 6. The off beat plywood's frequency should be higher if the athlete's weight is lighter; once upon start to final jump, the frequency with different weights tends similar. 7. The board point position spatial board frequency is 3.750 (Hz), and the board damping ratio is 1.5%-2.0%, obtained from the measurement by the acceleration sensor. Conclusions 1. In the true sense, person-board coupling should be the person's quality and the board quality becomes a whole one to move, and at this time the frequency is the person-board coupling frequency. During this time, the human center of gravity and the speed with the foot touching movement should be consistent in the vertical direction. 2. It is not the same for the different athlete's board impulse and the board's biggest reaction. With body weight increase, the athlete's impulse falling on the board will be bigger,and in turn the board reaction would correspondingly increase. 3. By observing the angular speed changes from the board buffering pedal extending, the hip, knee and malleolus joints simultaneously participated in the buffering, with the time order as the hip, the knee and the malleolus, which indicate that when human body needs to overcome the big resistance from pedal extends, the big joint first has the activity to deal with the resistance so that it causes the link to have the angle accelerated motion.

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. Dynamic research on diving athlete's person-board coupling when the off beat takes off[J]. Journal of medical biomechanics,2008,23(3):216-222

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