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Effects of altered loading states on muscle plasticity: what have we learned from rodents?This paper summarizes the key findings concerning the adaptive properties of rodent muscle in response to altered loading states. When the mechanical stress on the muscle is chronically increased, the muscle adapts by hypertrophying its fibers. This response is regulated by processes resulting in contractile protein expression reflecting slower phenotypes, thereby enabling the muscle to better support load-hearing activity. In contrast, reducing the load-bearing activity induces an opposite response whereby muscles used for both antigravity function and locomotion atrophy while transforming some of the slow fibers into faster contractile phenotypes. Accompanying the atrophy is both a reduced power generating and activity sustaining capability. These adaptive processes are regulated by both transcriptional and translational processes. Available evidence further suggests that the interaction of heavy resistance activity and hormonal/growth factors (insulin-like growth factor, growth hormone, glucocorticoids, etc.) are critical in the maintenance of muscle mass and function. Also resistance training, in contrast to other activities such as endurance running, provides a more economical form of stress because less mechanical activity is required to maintain muscle homeostasis in the context of chronic states of weightlessness.
Document ID
20040173131
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Baldwin, K. M.
(University of California Irvine 92717, United States)
Date Acquired
August 22, 2013
Publication Date
October 1, 1996
Publication Information
Publication: Medicine and science in sports and exercise
Volume: 28
Issue: 10 Suppl
ISSN: 0195-9131
Subject Category
Life Sciences (General)
Funding Number(s)
CONTRACT_GRANT: AR 30346
CONTRACT_GRANT: HL 38819
Distribution Limits
Public
Copyright
Other
Keywords
Non-NASA Center
NASA Discipline Number 00-00
NASA Program Flight
NASA Discipline Musculoskeletal

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