Effect of eccentric and concentric contraction mode on myogenic regulatory factors expression in human vastus lateralis muscle.

Skeletal muscle contractions are caused to release myokines by muscle fiber. This study investigated the myogenic regulatory factors, as MHC I, IIA, IIX, Myo-D, MRF4, Murf, Atrogin-1, Decorin, Myonection, and IL-15 mRNA expression in the response of eccentric vs concentric contraction. Eighteen healthy men were randomly divided into two eccentric and concentric groups, each of 9 persons. Isokinetic contraction protocols included maximal single-leg eccentric or concentric knee extension tasks at 60°/s with the dominant leg. Contractions consisted of a maximum of 12 sets of 10 reps, and the rest time between each set was 30 s. The baseline biopsy was performed 4 weeks before the study, and post-test biopsies were taken immediately after exercise protocols from the vastus lateralis muscle. The gene expression levels were evaluated using Real-Time PCR methods. The eccentric group showed a significantly lower RPE score than the concentric group (P ≤ 0.05). A significant difference in MyoD, MRF4, Myonection, and Decorin mRNA, were observed following eccentric or concentric contractions (P ≤ 0.05). The MHC I, MHC IIA, IL-15 mRNA has been changed significantly compared to the pre-exercise in the concentric group (P ≤ 0.05). While only MHC IIX and Atrogin-1 mRNA changed significantly in the eccentric group (P ≤ 0.05). Additionally, the results showed a significant difference in MyoD, MRF4, IL-15, and Decorin at the follow-up values between eccentric or concentric groups (P ≤ 0.05). Our findings highlight the growing importance of elucidating the different responses of muscle growth factors associated with a myogenic activity such as MHC IIA, Decorin, IL-15, Myonectin, Decorin, MuRF1, and MHC IIX mRNA in following various types of exercise.