Knee extension strength and vertical jumping performance in nordic combined athletes

Background. The purpose of this study was to measure knee extension strengt h and vertical jumping performance characteristics in nordic combined athle tes. Methods. Unilateral knee extension isometric maximal force (MF) and rate of force development (RFD) were measured by a special dynamometer, and unilat eral isokinetic peak torque (PT) at angular velocities of 60 and 180 deg/se c by a Cybex II dynamometer. Maximal squat (SJ) and counter-movement jumps (CMJ) were performed on force platform. Nine nordic combined athletes as th e experimental group and 12 untrained male university students as the contr ol group participated. Results. Nordic combined athletes had a greater (p <0.05) absolute and rela tive (body mass-related) values of knee extension isometric MF and isokinet ic PT, isometric RFD as well as jumping height in SJ and CMJ, than controls . The jumping height in CMJ was greater (p <0.05) compared with SJ only in nordic combined athletes. Jumping height in SJ and CMJ correlated significa ntly (p <0.05) with knee extension isometric RFD (r=0.62-0.83) and isokinet ic PT at angular velocity of 60 deg/sec (r=0.70-0.82) in nordic combined at hletes and untrained men. No significant correlation was obtained between u nilateral knee extension isometric MF and isokinetic PT or vertical jumping height. Conclusions. The present study demonstrated a markedly higher voluntary max imal and explosive force-generating capacity of the extensor muscles of low er extremities in nordic combined athletes compared with untrained men, whi ch indicates the adaptation to specific explosive type of strength training .