Int J Sports Med 2004; 25(5): 332-338
DOI: 10.1055/s-2004-815841
Physiology & Biochemistry

© Georg Thieme Verlag KG Stuttgart · New York

The Effect of Mechanical Loading on the MyHC Synthesis Rate and Composition in Rat Plantaris Muscle

A. Pehme1 , K. Alev1 , P. Kaasik1 , A. Julkunen2 , T. Seene1
  • 1Department of Functional Morphology, University of Tartu, Estonia
  • 2Department of Clinical Chemistry, University of Kuopio, Finland
Further Information

Publication History

Accepted after revision: August 8, 2003

Publication Date:
18 May 2004 (online)


The aim of this study was to investigate the response of protein synthesis rate, particularly myosin heavy chain (MyHC) isoforms synthesis and the magnitude of its isoform transformation in fast-twitch plantaris muscle, to different modes of prolonged mechanical loading. Different protocols of mechanical loading were used: resistance training (RT), compensatory hypertrophy (CH) of m. plantaris after tenotomy of m. gastrocnemius and a combination of the two previous loadings (RT + CH). During the different modes of loading, plantaris muscle hypertrophy in RT group was ∼ 10 %, CH ∼ 40 % and CH + RT ∼ 44 %. MyHC I and IID isoform synthesis rate increased in all experimental groups, as well as their relative content. MyHC IIA relative content decreased during RT and RT + CH and increased during CH. MHC IIB isoform relative content decreased in all experimental groups, but compared with CH in CH + RT MyHC IIB isoform content increased in plantaris muscle. These results demonstrate that different modes of mechanical loading resulted in the selective up- and down-regulation of MyHC isoforms in fast-twitch skeletal muscle. The synthesis rate and relative content of the two fastest isoforms of MyHC IIB and IID are regulated to different directions during mechanical loading.


Ando Pehme

Department of Functional Morphology, University of Tartu

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