title: Endurance Exercise Enhances the Effect of Strength Training on Muscle Fiber Size and Protein Expression of Akt and mTOR.
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.
authors.affiliation: Swedish Winter Sports Research Centre, Department of Health Sciences, Mid Sweden University, Östersund, Sweden.
authors.forename: Zuzanna
authors.initials: Z
authors.lastname: Kazior
authors.affiliation: Swedish Winter Sports Research Centre, Department of Health Sciences, Mid Sweden University, Östersund, Sweden.
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Willis
authors.affiliation: Swedish School of Sport and Health Sciences, Stockholm, Sweden.
authors.forename: Marcus
authors.initials: M
authors.lastname: Moberg
authors.affiliation: Swedish School of Sport and Health Sciences, Stockholm, Sweden.
authors.forename: William
authors.initials: W
authors.lastname: Apró
authors.affiliation: Department of Physical Education, University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Spain.|Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, Las Palmas de Gran Canaria, Canary Island, Spain.
authors.forename: José A L
authors.initials: JA
authors.lastname: Calbet
authors.affiliation: Swedish Winter Sports Research Centre, Department of Health Sciences, Mid Sweden University, Östersund, Sweden.
authors.forename: Hans-Christer
authors.initials: HC
authors.lastname: Holmberg
authors.affiliation: Swedish School of Sport and Health Sciences, Stockholm, Sweden.
authors.forename: Eva
authors.initials: E
authors.lastname: Blomstrand
mesh_terms: D000328:Adult; D001706:Biopsy; D015444:Exercise; D006801:Humans; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000502:physiology*; D009124:Muscle Proteins / Q000378:metabolism; D053580:Muscle Strength; D010101:Oxygen Consumption; D010807:Physical Endurance; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D055070:Resistance Training; D015398:Signal Transduction; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism*
chemical_list: D009124:Muscle Proteins; D012333:RNA, Messenger; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases