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

• Published in: International journal of sports medicine 2004-08, Vol.25 (6), p.438-445
• Main Authors: Seene, T., Kaasik, P., Alev, K., Pehme, A., Riso, E. M.
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Contractile Proteins - analysis; Contractile Proteins - metabolism; Fundamental and applied biological sciences. Psychology; Male; Muscle, Skeletal - metabolism; Myosin Heavy Chains - analysis; Myosin Heavy Chains - metabolism; Physical Endurance - physiology; Physiology & Biochemistry; Protein Isoforms - analysis; Protein Isoforms - metabolism; Random Allocation; Rats; Rats, Wistar; Running - physiology; Time Factors; Vertebrates: body movement. Posture. Locomotion. Flight. Swimming. Physical exercise. Rest. Sports
• ISSN: 0172-4622; 1439-3964
• DOI: 10.1055/s-2004-820935

Abstract 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.