Single muscle fiber properties in aging and disuse

M. Canepari, M. A. Pellegrino, G. D'Antona, R. Bottinelli

Research output: Contribution to journalArticlepeer-review


Since the middle of the 1980s, it was understood that myosin, the motor of contraction, can be expressed in several isoforms. The isoforms of the myosin heavy-chain (MHC) portion of the molecule were found to be mostly responsible for the diversity in the contractile and energetic properties of muscle fibers. In humans, three MHC isoforms are expressed in limb muscles (MHC-1, MHC-2A and MHC-2X) and they generate three pure fiber types (types 1, 2A and 2X) and two hybrid types (types 1-2A and -2AX). Type 1, 2A and 2X fibers widely differ with respect to most of their contractile and energetic properties, and a change in their relative distribution within muscles is known to modulate their functional properties in vivo through a "qualitative" mechanism. On the basis of the MHC regulation of muscle fibers properties, it is expected that a given fiber type develops the same force and shortens at the same speed regardless of the physiologic and pathologic conditions under which the muscle works. Surprisingly, several evidences have been accumulating to show that in aging and disuse, the properties of a muscle fiber type can change with no change in its myosin isoform content. This short review considers the latter phenomenon and the possible underlying mechanisms.

Original languageEnglish
Pages (from-to)10-19
Number of pages10
JournalScandinavian Journal of Medicine and Science in Sports
Issue number1
Publication statusPublished - Feb 2010


  • Aging
  • Disuse
  • Muscle fibers
  • Myosin isoforms

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine
  • Physical Therapy, Sports Therapy and Rehabilitation


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