title: Controlled intermittent shortening contractions of a muscle-tendon complex: muscle fibre damage and effects on force transmission from a single head of rat EDL.
abstract: This study was performed to examine effects of prolonged (3 h) intermittent shortening (amplitude 2 mm) contractions (muscles were excited maximally) of head III of rat extensor digitorum longus muscle (EDL III) on indices of muscle damage and on force transmission within the intact anterior crural compartment. Three hours after the EDL III exercise, muscle fibre damage, as assessed by immunohistochemical staining of structural proteins (i.e. dystrophin, desmin, titin, laminin-2), was found in EDL, tibialis anterior (TA) and extensor hallucis longus (EHL) muscles. The damaged muscle fibres were not uniformly distributed throughout the muscle cross-sections, but were located predominantly near the interface of TA and EDL muscles as well as near intra- and extramuscular neurovascular tracts. In addition, changes were observed in desmin, muscle ankyrin repeat protein 1, and muscle LIM protein gene expression: significantly (P<0.01) higher (1.3, 45.5 and 2.3-fold, respectively) transcript levels compared to the contralateral muscles. Post-EDL III exercise, length-distal force characteristics of EDL III were altered significantly (P<0.05): at high EDL III lengths, active forces decreased and the length range between active slack length and optimum length increased. For all EDL III lengths tested, proximal passive and active force of EDL decreased. The slope of the EDL III length-TA+EHL force curve decreased, which indicates a decrease of the degree of intermuscular interaction between EDL III and TA+EHL. It is concluded that prolonged intermittent shortening contractions of a single head of multi-tendoned EDL muscle results in structural damage to muscle fibres as well as altered force transmission within the compartment. A possible role of myofascial force transmission is discussed.
authors.affiliation: Instituut voor Fundamentele and Klinische Bewegingswetenschappen, Faculteit Bewegingswetenschappen, Vrije Universiteit , Van der Boechorststraat 9, 1081 BT Amsterdam, The Netherlands.
authors.forename: Huub
authors.initials: H
authors.lastname: Maas
authors.forename: T Maarit
authors.initials: TM
authors.lastname: Lehti
authors.forename: Vendla
authors.initials: V
authors.lastname: Tiihonen
authors.forename: Jyrki
authors.initials: J
authors.lastname: Komulainen
authors.forename: Peter A
authors.initials: PA
authors.lastname: Huijing
mesh_terms: D000818:Animals; D003893:Desmin / Q000235:genetics; D020869:Gene Expression Profiling; D008297:Male; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D023421:Models, Animal; D008969:Molecular Sequence Data; D009119:Muscle Contraction / Q000502:physiology*; D018485:Muscle Fibers, Skeletal / Q000473:pathology* / Q000502:physiology; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology*; D009929:Organ Size; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013314:Stress, Mechanical; D013710:Tendons / Q000502:physiology*; D013997:Time Factors; D033921:Vesicular Transport Proteins
chemical_list: D003893:Desmin; C512942:Marcksl1 protein, rat; D008565:Membrane Proteins; D009124:Muscle Proteins; D012333:RNA, Messenger; D033921:Vesicular Transport Proteins