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1 Section of Sports and Rehabilitation Medicine, Department of Medicine II, University of Ulm, D-89070 Ulm; 2 Institute of Sports Sciences, Department 1: Sport and Movement, Johann-Wolfgang-Goethe University, 60054 Frankfurt am Main; and 3 Eden-Reha, Rehabilitation Clinic, 93093 Donaustauf, Germany
Myosin heavy chain (MHC)
isoform expression changes with physical training. This may be
one of the mechanisms for muscular adaptation to exercise. We aimed to
investigate the effects of different strength-training protocols on MHC
isoform expression, bearing in mind that
- MHCslow
(newly identified MHC isoform) mRNA may be upregulated in response to
training. Twelve volunteers performed a 6-wk strength training with
maximum contractions (Max group), and another 12 of similar age
performed combination training of maximum contractions and ballistic
and stretch-shortening movements (Combi group). Muscle samples were
taken from triceps brachii before and after training. MHC isoform
composition was determined by SDS-PAGE silver staining, and mRNA levels
of MHC isoforms were determined by RT-PCR. In Max group, there
was an increase in MHC2A (49.4 to 66.7%, P < 0.01) and a decrease in MHC2X (33.4 to 19.5%, P < 0.01) after training, although there was no
significant change in MHCslow. In Combi group, there was
also an increase in MHC2A (47.7 to 62.7%,
P < 0.05) and a decrease in MHCslow (18.2 to 9.2%, P < 0.05) but no significant change in
MHC2X. An upregulation of
-MHCslow mRNA was,
therefore, found in both groups as a result of training. The strength
training with maximum contractions led to a shift in MHC isoform
composition from 2X to 2A, whereas the combined strength training
produced an MHC isoform composition shift from slow to 2A.
skeletal muscle; exercise;
-myosin heavy chain slow
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