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EFFECTS OF MUSCLE DAMAGE ON STRETCH-SHORTENING CYCLE FUNCTION AND MUSCLE STIFFNESS CONTROL

HARRISON ANDREW J.; GAFFNEY, SIMON D.
The Journal of Strength & Conditioning Research: November 2004
ORIGINAL RESEARCH: PDF Only

ABSTRACTThis experiment examined the effect of eccentric contraction–induced muscle damage on the stretch-shortening cycle and vertical leg spring stiffness during jumping activities. Ten moderately active male and female adult volunteers participated in this study (aged 23 6 2.3 years). Temporary muscle damage to the knee extensors was administered by a bout of eccentric contractions on an isokinetic dynamometer. Measurements were obtained of maximum voluntary force and of take-off velocities for single-leg countermovement jumps (CMJs), squat jumps (SJs), and drop jumps (DJs), performed on a specially constructed sledge and force plate apparatus. These measurements were obtained before and after the damage intervention, and the undamaged leg was used as a control. The results indicated that eccentric muscle damage significantly affected stretch-shortening cycle performance by causing relatively greater reductions in SJ performance than CMJ or DJ. The muscle damage intervention also significantly increased leg-spring stiffness, which indicates that the changes in leg stiffness may be an important adaptation resulting from eccentric exercise.

This experiment examined the effect of eccentric contraction–induced muscle damage on the stretch-shortening cycle and vertical leg spring stiffness during jumping activities. Ten moderately active male and female adult volunteers participated in this study (aged 23 6 2.3 years). Temporary muscle damage to the knee extensors was administered by a bout of eccentric contractions on an isokinetic dynamometer. Measurements were obtained of maximum voluntary force and of take-off velocities for single-leg countermovement jumps (CMJs), squat jumps (SJs), and drop jumps (DJs), performed on a specially constructed sledge and force plate apparatus. These measurements were obtained before and after the damage intervention, and the undamaged leg was used as a control. The results indicated that eccentric muscle damage significantly affected stretch-shortening cycle performance by causing relatively greater reductions in SJ performance than CMJ or DJ. The muscle damage intervention also significantly increased leg-spring stiffness, which indicates that the changes in leg stiffness may be an important adaptation resulting from eccentric exercise.

Address correspondence to Dr. Drew Harrison, drew. harrison@ul.ie.

© 2004 National Strength and Conditioning Association