On The Moment Of Stretching Or Flexing Knees And The Results of Vertical Jumping

  • W. Zefang
Keywords: volleyball, force moment, jumping, landing

Abstract

Nineteen female and nine male volleyball players from a provincial team were tested for height of four different vertical jumps: free vertical jumping, deep-crouching vertical jumping, static-crouching vertical jumping, and vertical jumping with hands on the back. They were tested on a Kistler force platform and simultaneously flimed. A test for the moment of stretching .and flexing knees with the Cybex 350 isokinetic force testing machine at an . angular velocity of 0, 60, 120, 180, 240, 300 degrees/s. The results are: 1) When angular velocity increases, the following relative values decrease: a) the maximum moment of stretching or flexing knees, b) the total power, 3) when the knee joint angle is 90 or 120 degrees, the moment of stretching or flexing. 2) Comparing the four different vertical jumps, the free jump has the best results. 3) For females, the relative value of the maximum moment of stretching knees, the relative value of total work and average power are in direct ratio with the height of free jumping.