Molecular signaling in muscle

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Abstract:

Molecular signaling in muscle is affected by the specificity of resistance

exercise protocol.

Scand J Med Sci Sports. 2010 Sep 9. doi: 10.1111/j.1600-0838.2010.01198.x. [Epub

ahead of print]

Hulmi JJ, S, Ahtiainen JP, Nyman K, Kraemer WJ, Häkkinen K.

Abstract

Mammalian target of rapamycin and mitogen-activated protein kinase (MAPK)

signaling pathways have been highlighted as important for muscle adaptations and

thus, they may distinguish adaptations to different exercises. Typically,

resistance exercise designed for muscle hypertrophy has moderate intensity

(60-80% of one repetition maximum, 1 & #8195;RM) while one prioritizing maximal

strength with minor hypertrophy has a higher intensity ( & #8805;90% of

1 & #8195;RM). Eight untrained men (28.4±3.7 years) conducted two different

bilateral leg press exercise protocols: hypertrophic (5 × 10 & #8195;RM) and pure

maximal strength (15 × 1 & #8195;RM) in a counterbalanced, cross-over design with

1 week between exercises. Vastus lateralis muscle biopsies were taken before and

0.5 & #8195;h after resistance exercise, or in six controls (26.5±3.6 years) who

rested. The phosphorylation of p70S6K (Thr(421) /Ser(424) ), rpS6 (Ser(240/244)

and Ser(235/236) ) and MAPK p38 as increased ( & #8764;2-16 fold) after both

exercise protocols. However, the phosphorylation of MAPK Erk1/2 and p70S6K at

Thr(389) increased only after 5 × 10 & #8195;RM. The increase in the

phosphorylation of p70S6K (Thr(421) /Ser(424) ), rpS6 (Ser(235/236) ) and Erk1/2

were higher after 5 × 10 & #8195;RM (P<0.05). No changes were seen in controls.

In conclusion, MAPK signaling is greater after hypertrophic than maximal

strength exercise protocol. This may mediate adaptations specific to these

different types of training regimens.

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Carruthers

Wakefield, UK