Document Detail

Dynamic contractility and efficiency impairments in stretch-shortening cycle are stretch-load dependent after training-induced muscle damage.
MedLine Citation:
PMID:  23207890     Owner:  NLM     Status:  Publisher    
ABSTRACT: To determine the acute task- and stretch load-dependency of neuromuscular impairments after muscle-damaging exercise, we examined the magnitude of strength deficits in isometric and stretch-shortening cycle (SSC) contractions following a single bout of exercise. Ten trained males performed 90 unilateral isokinetic eccentric-concentric knee extensions on a dynamometer. Plasma creatine kinase activity, muscle soreness, maximal isometric torque, short-range stiffness and peak torque in the eccentric phase of the SSC contraction at three stretch loads (120, 150 and 180 Joule) were determined in the quadriceps before, and 24 hours after exercise. During SSC, positive mechanical work and efficiency were also calculated. Creatine kinase and soreness increased at 24h (p < 0.05). In each of the three stretch-load conditions, muscle damage affected short-range stiffness less than isometric and peak SSC torque (p < 0.05), providing evidence for a selective impairment in contractile function after muscle damage. With greater SSC stretch-load peak SSC torque deficit increased linearly, while short-range stiffness deficit was unaffected. Efficiency declined only at the 180 Joule condition (p < 0.05) as a result of decreased positive work (p < 0.05). It was concluded that intense exercise produced microtrauma in the muscle, as well as a selective loss of force generating capacity, which suggests greater damage to the contractile machinery. Practitioners may expect greater acute impairment of force generation in movements that use large loads in their daily training drills. However, altered knee flexion strategy during SSC may compensate for the force deficit, preserving mechanical efficiency at smaller stretch-loads.
Váczi Márk; Rácz Levente; Hortobágyi Tibor; Tihanyi József
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-11-30
Journal Detail:
Title:  Journal of strength and conditioning research / National Strength & Conditioning Association     Volume:  -     ISSN:  1533-4287     ISO Abbreviation:  J Strength Cond Res     Publication Date:  2012 Nov 
Date Detail:
Created Date:  2012-12-4     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9415084     Medline TA:  J Strength Cond Res     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
1Institute of Physical Education and Sport Science, University of Pécs, Hungary 2Department of Biomechanics, Faculty of Physical Education and Sport Science, Semmelweis University, Hungary 3Center for Human Movement Sciences, University Medical Center Groningen, University of Groningen, The Netherlands.
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