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Title: Endurance exercise enhances the effect of strength training on muscle fiber size and protein expression of akt and mTOR
Authors: Kazior, Zuzanna
Willis, Sarah J.
Moberg, Marcus
Apró, William
Calbet, Jose A. L. 
Holmberg, Hans-Christer
Blomstrand, Eva
UNESCO Clasification: 241106 Fisiología del ejercicio
Keywords: Human Skeletal-Muscle
Resistance Exercise
Adenosine Triphosphatase
Contractile Activity, et al
Issue Date: 2016
Journal: PLoS ONE 
Abstract: Reports concerning the effect of endurance exercise on the anabolic response to strength training have been contradictory. This study re-investigated this issue, focusing on training effects on indicators of protein synthesis and degradation. Two groups of male subjects performed 7 weeks of resistance exercise alone (R; n = 7) or in combination with preceding endurance exercise, including both continuous and interval cycling (ER; n = 9). Muscle biopsies were taken before and after the training period. Similar increases in leg-press 1 repetition maximum (30%; P<0.05) were observed in both groups, whereas maximal oxygen uptake was elevated (8%; P<0.05) only in the ER group. The ER training enlarged the areas of both type I and type II fibers, whereas the R protocol increased only the type II fibers. The mean fiber area increased by 28% (P<0.05) in the ER group, whereas no significant increase was observed in the R group. Moreover, expression of Akt and mTOR protein was enhanced in the ER group, whereas only the level of mTOR was elevated following R training. Training-induced alterations in the levels of both Akt and mTOR protein were correlated to changes in type I fiber area (r = 0.55-0.61, P<0.05), as well as mean fiber area (r = 0.55-0.61, P<0.05), reflecting the important role played by these proteins in connection with muscle hypertrophy. Both training regimes reduced the level of MAFbx protein (P<0.05) and tended to elevate that of MuRF-1. The present findings indicate that the larger hypertrophy observed in the ER group is due more to pronounced stimulation of anabolic rather than inhibition of catabolic processes.
ISSN: 1932-6203
DOI: 10.1371/journal.pone.0149082
Source: PLoS ONE [EISSN 1932-6203], v. 11 (2), (Febrero 2016)
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