Long-term effects of spinal cord transection on fast and slow rat skeletal muscle. II. Morphometric properties

Richard L. Lieber*, Jan O. Fridén, Alan R. Hargens, Earl R. Feringa

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

85 Scopus citations


Morphometric properties of rat soleus and extensor digitorum longus muscles were studied 1 year following complete thoracic spinal cord transection (spinal cord level T9). Both muscles demonstrated almost complete type 1 to type 2 muscle fiber type conversion after 1 year. Muscle fiber atrophy was observed in both muscles. Type 2 fiber atrophy occurred to about the same extent in both muscles. Atrophy was most severe for the soleus type 1 fibers (50% decrease in size). Calculations based on the fiber type and size changes observed indicate that the percentage of the muscle cross-sectional area occupied by each fiber type was almost the same for both muscles 1 year after transection. Discriminant analysis of the data indicated that the percentage of type 2 fibers present in the muscle was the best discriminator between the various groups. These morphometric data provided a basis for understanding the contractile results presented in the previous study as well as insights into the mechanism of transformation in skeletal muscle. Furthermore, inherent differences between type 1 and type 2 fibers were demonstrated between predominantly slow and predominantly fast muscles. Thus, after almost one-half a lifetime of transection, rat muscles are almost completely transformed to fast muscle, and, regardless of initial conditions, have nearly identical properties.

Original languageEnglish (US)
Pages (from-to)435-448
Number of pages14
JournalExperimental Neurology
Issue number3
StatePublished - Mar 1986

ASJC Scopus subject areas

  • Neurology
  • Developmental Neuroscience


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