• J. Szeles
  • J. Tihanyi


The aim of the study was to investigate the effect of different ranges of knee flexion and extension on the maximum vertical velocity (Vmax) during squatting jumps (SQ) and counter movement jumpsCMJ). Ten well trained male students were involved in the study. The subjects were instructed to carry out SQ-s and CMJ-s with several ranges of knee angular displacement (SQ50, SQ90, SQ135,CMJSO, CMJ90, CMJ135). Sel spot motion analyser and a Kistler force plate were used to measure the angular displacement of the knee joint, the vertical displacement of the selected parts of the body and ground reaction forces. The subjects carried out three to five jumps at each type of SQ and CMJ. Vmax of positive phase of 'umps was calculated by Sel spot (SVmax). Vmax was also calculated from the flying time (KVmax) obtained from the force-time curves. Conventional mathematical statistics were applied including means, SD and Student's t-test. Average values for SVmax were significantly higher (p < 0.05) than KVmax in each type of vertical jumps. The reason of these differences attributes to the main findings of the study. Namely, the subjects only could use a certain range of joint extension to the48.3 (SQ90) for the subjects. It means that Vmax was attained far before the contact phase ended. This so called effective range cannot be used up when the starting knee angle is over 135 degrees. That is the reason why the effective range at SQ135 is significantly smaller than it is at SQSO- and SQ90, i.e. 32.2 degrees. Still, it does not mean that the effective range of extension lasts till the full extension of knee. SVmax was reached when the knee angle was 154.1(SQ) and148.4(CMJ) degrees. In our opinion this is probably due to neurophisyologicaland muscle-mechanical reasons.