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Repeated bouts of resistance training with short interval activate Akt‐mTOR signaling, but not protein synthesis in mouse skeletal muscle
Author(s) -
Takegaki Junya,
Arihara Yuki,
Ogasawara Riki,
Tsutaki Arata,
Nakazato Koichi,
Ishii Naokata
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.1009.7
Subject(s) - protein kinase b , overtraining , pi3k/akt/mtor pathway , isometric exercise , phosphorylation , puromycin , skeletal muscle , endocrinology , contraction (grammar) , resistance training , protein biosynthesis , medicine , chemistry , biology , signal transduction , microbiology and biotechnology , biochemistry , physical therapy , athletes
Resistance training activates Akt‐mTOR signaling pathway, thereby stimulates the protein synthesis within skeletal muscle. However, insufficient recovery period between training bouts may lead to the accumulation of fatigue, known as “overtraining”. Purpose To obtain an insight into the mechanism of overtraining, changes in muscle protein synthesis and Akt‐mTOR signaling activity were investigated with changing the interval between training bouts. Methods Male C57BL/6J mice were randomly assigned into four groups: Control (Cont), resistance‐trained with 3 bouts at interval of 72h (72H), 24h (24H) and 8h (8H). The resistance exercise consisted of 50 repetitions of maximal isometric contraction of the tibialis anterior muscle. The muscle contraction was induced by transcutaneous electrical stimulation of deep fibular nerve under anesthesia. Muscle samples were collected 6h after the final exercise session, and kept frozen until analysis. Fifteen minutes prior to the muscle sampling, mice were injected with 0.04 μmol/g puromycin. Results Phosphorylation of Akt and p70S6K was observed in 24H and 8H, and that in 8H was significantly higher than in 24H. The phosphorylation of rpS6 was observed in all exercised groups, and was higher in 24H and 8H than in other groups. Puromycin‐incorporated proteins, i.e., newly synthesized proteins in ribosomes, increased in 72H, but not in 24H and 8H. Conclusion The present results suggest that bouts of resistance training with interval shorter than 24h do not cause an increase in protein synthesis, even though activate Akt‐mTOR signaling pathway.