Impact of repeated bouts of eccentric exercise on myogenic gene expression

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Eur J Appl Physiol. 2007 Jul 20

Impact of repeated bouts of eccentric exercise on myogenic gene

expression.

Costa A, Dalloul H, Hegyesi H, Apor P, Csende Z, Racz L, Vaczi M,

Tihanyi J.

Department of Biomechanics, Faculty of Physical Education and Sport

Sciences, Semmelweis University, Budapest, Hungary,

Evidence indicates that repeated-bouts of eccentric exercise (EE) do

not exacerbate the extent of muscle damage indices, as compared to a

single-bout. We hypothesized that molecular adaptations, under

repeated-bouts of EE, would include suppression of muscle repair

inhibitory factors such as myostatin and up-regulation of muscle

repair positive regulatory factors such as myogenic regulatory

factors (MRFs).

Fifteen males were recruited for this study. The exercise group (n =

9) successfully completed six sets of 15 reps of maximum voluntary

eccentric contractions, for six consecutive days, using a

dynamometer (Multicont-II). Blood and muscle biopsy samples were

obtained from each subject 1 week prior to exercise, 2 days post the

first training session, and 24 h after the last training session.

Gene expression levels were determined using real-time RT-PCR. Blood

samples were analyzed for creatine kinase (CK) and lactate-

dehydrogenase (LDH) activity. Repeated-bouts of EE induced a large

down-regulation of myostatin mRNA (-73%) which persisted throughout

the study.

The responses of MRFs were mild. At day 3 only myogenin increased

significantly (1.9 fold) while MyoD decreased by 45%. Surprisingly,

at day 7, despite the presence of muscle damage indices, all MRFs

returned to the pre-exercise levels. The results of the present

study showed that repeated-bouts of EE, for six consecutive days,

dramatically decreased Myostatin mRNA expression but impaired the

expression patterns of MRFs such that, with the exception of

myogenin that showed a moderate non-sustained increase, MyoD and

MYf5 response was minimal.