Effects of concentric and eccentric muscle actions on serum myostatin and follistatin-like related gene levels.

The 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 PointsEccentric muscle actions do not preferentially increase serum myostatin.Increases in serum myostatin in response to eccentric muscle actions are associated with increase in serum FLRG.Increases in serum myostatin and FLRG in response to eccentric muscle actions are not correlated to serum cortisol.