Eccentric Strength Training Upregulated MHC I[alpha] mRNA in Human Skeletal Muscle: 10:00AM-10:15AM: 618

Transformation of myosin heavy chain isoforms (MHC) serves as an important mechanism for muscular adaptation to exercise. We have previously shown that a concentric strength training could upregulate MHC Iα mRNA in human skeletal muscle along with a transformation of MHC isoforms from fast to slow type, indicating that MHC Iα may have an role in the muscular adaptation to exercise. However, the effect of an eccentric strength training (EST) on MHC Iα mRNA in human skeletal muscle has not been reported.

PURPOSE: To investigate the effect of an eccentric strength training on MHC Iα mRNA in human skeletal muscle.

METHODS: Ten physically active and experienced sports students (aged 24 ±2 yrs, body mass 77±7 kg; 5 subjects each group (control vs. EST)) were included in this study. In the EST group, in addition to the usual physical activity of the sports students, a six-week EST with supramaximal load (leg press; 3 units/week, 5 series/unit, 3 repetitions/series) was undertaken. Muscle samples were obtained from m. vastus lateralis before after EST. For determination of MHC Iα mRNA level a real-time PCR was performed.

RESULTS: In the control group, there was no significant change in maximum strength (1RM) and MVC (maximum voluntary contraction) as well as in MHC Iα mRNA. In the EST group, 1RM increased from 97.8±31.2 kg to 123.4±27.7kg (P<0.05), MVC did not change significantly. MHC Iα mRNA level increased in the EST group by 217% after EST in comparison to the level before EST (P<0.03).

CONCLUSIONS: An eccentric strength training with supramaximal load improved significantly maximum muscle strength (1RM), but did not change the MVC in the experienced physically active subjects. This training upregulated significantly MHC Iα mRNA level in the trained human muscle. Since MHC Iα is considered as an intermediate between MHC Iα and MHC Iβ and expressed during MHC transformation, the upregulation of MHC Iα mRNA may suggest an important role of the MHC transformation in the muscular adaptation to exercise in human beings.