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present study determined the effects of concentric and eccentric muscle
actions on the contents of serum myostatin and follistatin-like related
gene (FLRG). Eight untrained males performed one exercise bout with
each leg, separated by three weeks. One bout consisted of 7 sets of
10 repetitions of eccentric muscle actions of the knee extensors at
150% of the concentric 1-RM while the other bout consisted of 7 sets
of 10 repetitions of concentric muscle actions at 75% 1-RM. The legs
used and the bouts performed were randomized. Five days prior to each
exercise bout, baseline measurements were taken for muscle strength.
For both bouts, a venous blood sample was obtained immediately prior
to exercise and again at 6, 24, and 48 hr post-exercise. Data were
analyzed with 2 X 4 (bout x test) ANOVA (p < 0.05). Increases in
serum myostatin and FLRG occurred with each exercise bout and, excluding
48 hr post-exercise, were significantly correlated to one another
(p < 0.05). After eccentric exercise, peak increases of 68% and
50% (p < 0.05) were observed for myostatin and FLRG, respectively.
Similar increases of 54% and 44% (p < 0.05) were observed after
concentric muscle actions. There was no significant difference in
expression of myostatin or FLRG as a function of muscle action type.
Our results suggest that a single bout of exercise with either eccentric
or concentric muscle actions appear to elicit a similar increase in
serum myostatin and FLRG. Therefore, the type of muscle action may
not be as much a mitigating factor for increasing serum myostatin
and FLRG rather than the muscle action per se.
KEY
WORDS: Muscle injury, cytokine, muscle proteolysis, resistance
exercise.
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