Int J Sports Med 2004; 25(6): 438-445
DOI: 10.1055/s-2004-820935
Physiology & Biochemistry

© Georg Thieme Verlag KG Stuttgart · New York

Composition and Turnover of Contractile Proteins in Volume-Overtrained Skeletal Muscle

T. Seene1 , P. Kaasik1 , K. Alev1 , A. Pehme1 , E. M. Riso1
  • 1Department of Functional Morphology, University of Tartu, Tartu, Estonia
Further Information

Publication History

Accepted after revision: August 10, 2003

Publication Date:
02 September 2004 (online)


The purpose of this study was to find the composition shift of myosin heavy chain (MyHC) isoforms in overtraining in fast- and slow-twitch skeletal muscles and different changes in MyHC isofom composition, synthesis and turnover rate between 4-week and 6-week overtraining. Male Wistar rats were randomly assigned to 4-week and 6-week endurance training, 4-week and 6-week overtraining groups. Plantaris (Pla), extensor digitorum longus (EDL), and soleus (Sol) muscles were studied. Daily excretion of 3-methylhistidine (3-MeHis) pool as an indicator for protein degradation increased in the 4-week and 6-week overtraining group to 4.04 ± 0.21 and 4.32 ± 0.23 %/day subsequently in comparison with the control group (2.16 ± 14 %/day, p < 0.001). In Pla muscle MyHC I isoform synthesis rate was 33 200 ± 2150 (after 6-week overtraining 27 100 ± 1800, p < 0.05), IIa 32 600 ± 2100; IId 27 300 ± 1890 and IIb isoform 20 100 ± 1600 (after 6-week overtraining 15 500 ± 1400, p < 0.05) dpm/M leucine/min. Actin synthesis rate increased in fast-twitch muscles during 4- and 6-week overtraining, and in soleus muscle during 6-week overtraining. In EDL and Sol muscle MyHC isoform composition during 6-week overtraining did not change significantly. During the 6-week overtraining the relative content of MyHC I and IIb isoforms decreased and IIa and IId isoforms increased in Pla muscle. The initial increase of MyHC IIb isoform after 4-week overtraining shows the higher stability of this isoform in comparison with MyHC I isoform in fast-twitch muscles during high volume exercise.


Teet Seene

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