Knee extension strength and vertical jumping performance in nordic combined athletes.

BACKGROUND The purpose of this study was to measure knee extension strength and vertical jumping performance characteristics in nordic combined athletes. METHODS Unilateral knee extension isometric maximal force (MF) and rate of force development (RFD) were measured by a special dynamometer, and unilateral isokinetic peak torque (PT) at angular velocities of 60 and 180 deg/sec by a Cybex II dynamometer. Maximal squat (SJ) and counter-movement jumps (CMJ) were performed on force platform. Nine nordic combined athletes as the experimental group and 12 untrained male university students as the control group participated. RESULTS Nordic combined athletes had a greater (p<0.05) absolute and relative (body mass-related) values of knee extension isometric MF and isokinetic 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 significantly (p<0.05) with knee extension isometric RFD (r=0.62-0.83) and isokinetic PT at angular velocity of 60 deg/sec (r=0.70-0.82) in nordic combined athletes and untrained men. No significant correlation was obtained between unilateral knee extension isometric MF and isokinetic PT or vertical jumping height. CONCLUSIONS The present study demonstrated a markedly higher voluntary maximal and explosive force-generating capacity of the extensor muscles of lower extremities in nordic combined athletes compared with untrained men, which indicates the adaptation to specific explosive type of strength training.