title: Morphological effects of resumption of loading after immobilization of skeletal muscles in lengthened position in female rats.
abstract: BACKGROUND
  In rehabilitation, immobilization of skeletal muscles in the elongated position is performed as a countermeasure in order to reverse the effects of severe muscle shortening and postoperative events. The return to normal functional activities is believed to stimulate mechanotransducers capable of reorganizing the normal muscle cytoarchitecture, but few data describing the histopathological changes relating to these procedures are available in the literature.
  
  
  OBJECTIVE
  To assess and quantify histological abnormalities induced by immobilization of the extensor digitorum longus (EDL) muscle in elongation and to compare them with free movement of the animal after this procedure.
  
  
  METHODS
  Eighteen female Wistar rats were used, divided into the following groups: Control; Immobilized in plantar flexion (EDL in an elongated position) for 14 days (GI); Immobilized for 14 days and released for 10 days (GIL). EDL fragments were frozen, sectioned and processed through immunohistochemical reactions for collagens I and III and histochemical methods for myofibrillar adenosine triphosphatase using hematoxylin-eosin.
  
  
  RESULTS
  GI animals presented slight increases in collagen I and fiber expression in a degenerative/necrotic process, and reductions in the proportion of FT2A fibers and in the diameters of all fiber types, compared with the controls. In GIL, the quantity of collagen I returned to control conditions; the proportion of FT2D decreased; the number of centralized nuclei increased; and the fiber diameter was smaller than in GI. However, FT2B and FT2D expression did not reach the reference values.
  
  
  CONCLUSIONS
  The data presented show that the recovery of function over a 10-day period was partially efficient with regard to recuperation of the characteristics of the EDL muscle after the period of immobilization. If the data are extrapolated to physiotherapeutic clinical practice, use of procedures directed towards primary dysfunctions of the muscle may favor a morphofunctional response in the segment and its full recovery.
authors.affiliation: Departamento de Biomecânica, Medicina e Reabilitação do Aparelho Locomotor, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brasil.
authors.forename: Juliana C
authors.initials: JC
authors.lastname: Polizello
authors.forename: Leonardo C
authors.initials: LC
authors.lastname: Carvalho
authors.forename: Fernando C
authors.initials: FC
authors.lastname: Freitas
authors.forename: Natália
authors.initials: N
authors.lastname: Padula
authors.forename: Edson Z
authors.initials: EZ
authors.lastname: Martinez
authors.forename: Ana C
authors.initials: AC
authors.lastname: Mattiello-Sverzut
mesh_terms: D000818:Animals; D005260:Female; D007103:Immobilization / Q000502:physiology*; D018482:Muscle, Skeletal / Q000473:pathology*; D011187:Posture; D051381:Rats; D017208:Rats, Wistar; D016474:Weight-Bearing