The purposes of this study were firstly to determine the relationship between the concentric isokinetic peak torque and the vertical-jumping indexes, secondly to observe the significant difference between the vertical-jumping indexes of squat jump (SJ) and counter-movement jump (CMJ), 17 mid-aged healthy males participated in this study. The concentric isokinetic peak torque (knee extension: 60 degree • s (-1) and 120 degree • s (-1)) of each subject was obtained by Cybex 6000. Then, the subjects performed SJs and CMJs three times individually with their maximal effort on the Kistler force plate. The vertical-jumping indexes, jump height (JH), maximal force (Fmax), maximal power (Pmax), SSI, RFD, total work (W), and the time to maximal force (Tmax), were computed by Bioware Performance Module Biomechanical Software Analysis System (version 1.0) on a computer. The JH, Tmax, & W were significantly different between CMJ and SJ (p＜.05); The E60p and E120p correlated to Fmax in SJ significantly (r=.677 & r=.730,. p＜.0l), and the E120p correlated to Pmax in SJ and CMJ (r=.654 & r=.687, p＜.0l). All the data suggest that: (1) To reach the Fmax more fast in CMJ resulted in greater height in CMJ than SJ; (2)The concentric isokinetic peak torque is not suitable to evaluate the performance of standing vertical jump; (3) There was no counter-movement to induce the stretch reflex in the activated muscle group during isokinetic torque tests.
