• V. Baltzopoulos


INTRODUCTION. The relationship between isokinetic tests of muscle function and performance in sporting activities is not clear. Some studies reported significant correlations between isokinetics and performance in swimming, cycling, skiing and other activities (Bosco, 1983), whereas others reported weak or non existing relationships in swimming, jumping, cycling and kicking (Mognoni, 1994). One of the main reasons for these contradictory findings is, according to our opinion, the failure of such studies to consider in detail the differences in the mechanical function of the neuromuscular system during the different activities. The purpose of this study, therefore, was to examine differences in muscle length and velocity between isokinetic tests and sport/functional activities. METHODS. Kinematic data from an isokinetic knee extension test, a running and a wallcing motion and a simulated kicking action were used to drive a detailed musculoskeletal model of the lower limbs using the Software for Interactive Musculoskeletal Modelling (Delp, 1995) on a Silicon Graphics workstation. This system enables the accurate estimation of musculotendinous unit length and velocity changes during the simulated activities. RESULTS. The length of the rectus femoris and patella tendon unit as well as the length of the semimembranosus during the different activities are shown in Figure 1. Figure 1. Rectus Femoris and Semimembranosus length during isokinetic dynamometry and different sport/ functional activities. It is evident from these data that there are considerable differences in the length and velocity of contraction in two of the most important and dominant knee extensor and flexor muscles. CONCLUSIONS These results indicate that there are significant neuromuscular mechanics differences between common sporting-functional activities and isokinetic exercise, indicating that such isolated joint-controlled velocity tests should not be used for specific training or performance prediction in the above activities. REFERENCES Bosco C. et al. (1983). Eur. J. App. Phys., 51 (3), 357-364. Mognoni P. et al. (1994). J. Sport. Med. Phys. Fitness, 34(4), 357-361. Delp S. and Loan P. (1995). Comput. Biol. Med., 25(1), 21-34.