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The effects of exercise training and denervation on the morphology of intrafusal muscle fibers

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The morphological effects of daily bouts of exercise and denervation on teres minor intrafusal muscle fibers were investigated in male Sprague-Dawley rats. After denervation, nuclear bag and nuclear chain muscle fiber cross-sectional area atrophied only 25 and 33% of the amount experienced by extrafusal fibers. Of the two fiber types, the nuclear chain fibers appeared to be more responsive to the effects of exercise than the nuclear bag fibers; however, this trend for enlargement had no statistical significance. Length measurements did not reveal any marked changes of any fiber type to the experimental conditions of this study. It was concluded that the possible differences in function and innervation of the nuclear bag and nuclear chain fibers could partly account for these findings.

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Supported in part by funds provided by the Graduate College.

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Maynard, J.A., Tipton, C.M. The effects of exercise training and denervation on the morphology of intrafusal muscle fibers. Int. Z. Angew. Physiol. Einschl. Arbeitsphysiol. 30, 1–9 (1971). https://doi.org/10.1007/BF00693719

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Key words

  • Muscle Spindle
  • Exercise Training