title: Effects of muscle damage on stretch-shortening cycle function and muscle stiffness control.
abstract: 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 +/- 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.
authors.affiliation: Department of Physical Education and Sport Sciences, University of Limerick, Limerick, Ireland. drew.harrison@ul.ie
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Harrison
authors.forename: Simon D
authors.initials: SD
authors.lastname: Gaffney
mesh_terms: D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D005260:Female; D006801:Humans; D007869:Leg Injuries / Q000503:physiopathology*; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000293:injuries*; D013314:Stress, Mechanical