Abstract
We examined signaling responses in the skeletal muscle of strength athletes after strength exercises under high and moderate load. Eight trained male powerlifters were recruited. The volunteers performed four sets of leg presses to volitional fatigue using a moderate load (65% 1‐repetition maximum [1RM]) for one leg, and a high load (85% 1RM) for the contralateral leg. The work volume performed by the leg moving a moderate load was higher than that of the contralateral leg moving a high load. Biopsy of the m. vastus lateralis was performed before, and at 1, 5, and 10 h after, cessation of exercise. Phosphorylation of p70S6kThr389, 4E‐BP1Thr37/46, and ACCS er79 increased after moderate load exercises, whereas phosphorylation of ERK1/2Thr202/Tyr204 increased, and that of eEF2Thr56 decreased, after high load exercises. Exercise under a moderate load and a high work volume activated mTORC1‐dependent signaling in trained skeletal muscle, whereas exercise under a high load but lower work volume activated the MEK‐ERK1/2 signaling cascade and eEF2.
Highlights
Strength training is practiced widely by those participating in sports, as well as by those undergoing rehabilitation or suffering illness
Strength training performed to volitional fatigue using high and moderate loads leads to similar levels of skeletal muscle hypertrophy in untrained (Popov et al 2006; Mitchell et al 2012) and strength trained men (Schoenfeld et al 2015; Morton et al 2016)
We found that phosphorylation of Mammalian target of rapamycin complex 1 (mTORC1) substrates increased after moderate load exercises, while phosphorylation of ERK1/ 2Thr202/Tyr204 increased, and that of eEF2Thr56 decreased, after high load exercises
Summary
Strength training is practiced widely by those participating in sports, as well as by those undergoing rehabilitation or suffering illness. The most significant variable in strength training is exercise load. It was suggested that this effect is associated with comparable muscle fiber recruitment and comparable rates of protein synthesis when performing exercises to fatigue under varying load (Burd et al 2010). Mammalian target of rapamycin complex 1 (mTORC1) is a key regulator of protein synthesis in skeletal muscle. Activation of mTORC1 in response to strength exercise results in phosphorylation of the translation initiation regulators ribosome protein S6 kinase (p70S6k) and Eukaryotic translation initiation factor 4E (eIF4E) - binding protein 1 (4E-BP1), and subsequent acceleration of protein synthesis (Goodman 2014). A specific inhibitor of mTORC1, called rapamycin, blocks increases in protein synthesis in the muscles of young recreationally active a 2019 The Authors.
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