DETERMINING THE FUNCTIONS UPON WHICH FORCE GENERATION VELOCITY AND ITS DIMENSIONS ARE CHANGED IN LEG EXTENSORS

Abstract

INTRODUCTION: The outcome of a judo combat depends on force generation velocity and the levels of its dimensions that vary throughout the combat according to the requirements arising from a specific situation. In order to program force generation velocity change and dimensions that it depends on in an individual, specially designed models are used to determine the principles according to which the followed values behave, in the interval between the beginning of generation and the achievement of maximum force. This was done in the present paper. METHODS: Functions upon which force generation velocity and its dimensions change in time in leg extensors were defined in a subject, top judoist and winner of gold and silver medals in Balkan, European and world competitions, aged 25, with body height BH = 1.91 m and body mass BM = 97.8 kg, using a special hardware-software designed at Police Academy in Belgrade. Force (N) was sampled under isometric conditions, at the angle of 115 degrees of flexion in knee joint, using Belt method (Everts,E.W. et all.,1938; Linfort,A. et all., 1971) at every millisecond. In our research we took data about force (Ft) and time (t) at every 1% of maximum force (Fmax). These data were used to calculate force generation velocity (FGV) expressed in Ns, for every % from 1 to 100. Its dimensions, such as muscle involvement velocity (C) expressed in absolute measures, and force generation velocity change (FGVS1) expressed in N/s, were also calculated for every % from 1 to 100. Force generation velocity change (FGVS2) expressed in N/s was calculated at an interval of 1%. Fitting, by least squares method, was used to determine the function forms affecting the followed values. RESULTS: In the experiment, the subject achieved Fmax of 6719.6 N at the time of 2.461 s. Fitting obtained the following functions that enabled determining the behaviour of force generation velocity and its components in the whole scope of force generation: FGV=1543.1Ln(t)+5604.5; C(t<0.2)=-220.04t2+58.732t+0.2286; C(t>0.2)=-0.0978t3 +1.0727t2 - 2.5403t+3.423; FGVS1(t<0.2)= -1E + 07t3 +2E+06t2-1721.4t-256.13; FGVS1(t>0.2)=1131.6t4-6607.5t3+13370t2-11042t+3344.3; FGVS2(t<0.2)=-179437t2+44792t-428.64; FGVS2(t>0.2) = 254.52t4 -1555.2t3+3484t2-3655.4t+2045.4. CONCLUSIONS: The obtained functions define the principles according to which force generation velocity and its dimensions behaved in the whole scope of generation in the individual subject. The functions are used to simulate the changes in the observed variables according to combat requirements, to design the training methods and to control the effects of the training.