Response of MyoD and MRF4 Myokines to Eccentric and Concentric Activity in Healthy Young Men

The present study aimed to investigate the response of MyoD and MRF4 myokines to eccentric and concentric activity in healthy young men. Ten healthy males were split into two groups of five, each with concentric and eccentric contractions. Excentric and concentric knee extension with a maximal power and angular velocity of 60 per second were used in isokinetic contraction protocols. The torque set for each subject was considered the same in both protocols to match the load, and the reciprocating speed was 60 degrees per second. At the beginning and end of the activity, the extensive biopsy was performed to examine the expression of the MyoD and MRF4 genes. The results showed that the intragroup changes of MRF4 after one session of activity were not significant in the eccentric (p = 0.229) and concentric (p = 0.178) groups. Furthermore, intergroup changes showed no difference between two groups (p = 0.182). Moreover, the changes within MyoD group after one activity session were significant in the eccentric group (p = 0.001) but not significant in the concentric group (p = 0.318). Moreover, intergroup changes showed no difference between the two groups (p = 0.821). In general, the present study showed that one session of eccentric and concentric activity leads to changes in the factors involved in skeletal muscle strength and hypertrophy. Besides, these changes were generally greater in the eccentric than concentric contraction. Therefore, it is recommended to focus more on concentric exercises to increase hypertrophy and muscle strength.