Myogenic Growth and Differentiation Factors in Eccentric Strength Training with Supramaximal Loads

Abstract

Strength training with supramaximal loads leads to maximal muscle load, but also to muscle damage and inflammation. We have previously shown that eccentric training induces slow-type MHC-transformation and therefore it is meaningful to examine the myogenic growth and differentiation factors Myogenin, MyoD and mechano-growth-factor (MGF) how they contribute to eccentric training effects. PURPOSE: To determine the effects of eccentric strength training with supramaximal loads on isometric, concentric and eccentric maximal strength and on Myogenin, MyoD and MGF. METHODS: Ten training-experienced college level athletes were included in the study: 5 received a 6-week strength training with supramaximal contractions, 5 performed maintained training without no specific strength training. Muscle samples were taken from M. vastus lateralis before, 3 days and 14 days after training. Strength was measured using 1RM (repetition maximum) and isometric MVC (maximum voluntary contractions). mRNA levels of Myogenin, MyoD and MGF expression were determined by quantitative real-time PCR. RESULTS: Myogenin expression was significantly increased after training: 3 days after training (506%), 14 days after training (951%) as well as MyoD (400% n.s. and 1402%s). MGF increased significantly in eccentric training. Concentric strength was significantly improved after eccentric strength training with supramaximal load (1RMfrom 97.82 ±31.15 kg to 123.44 ± 27.68 kg; p < 0.05). Isometric MVC was not changed in training group and decreased in control group. CONCLUSIONS: Eccentric strength training with supramaximal load leads to expression of stretch-induced MGF and MyoD which may be attributed to satellite cell activation. The differentiation factors, Myogenin and MGF for fast, and MyoD for slow show no difference so the expression of slow-type myosins may be attributed to other factors such as local inflammation.