title: Flywheel resistance exercise to maintain muscle oxidative potential during unloading.
abstract: BACKGROUND
  As spaceflight compromises skeletal muscle oxidative and aerobic work capacity, this study assessed the efficacy of resistance exercise (RE) to counteract muscle metabolic perturbations induced by 5 wk unilateral lower limb unloading (UL).
  
  
  METHODS
  There were 21 men and women (30-56 yr) who were randomly assigned to either UL with (Group, Grp; UL+RE; N = 10) or without (Grp UL; N = 11) concurrent RE. Iso-inertial RE comprised four sets of seven maximal coupled concentric-eccentric knee extensions executed 2-3 times per week. Percutaneous biopsies were obtained from m. vastus lateralis before and after either intervention. Levels of mRNA expression of factors regulating skeletal muscle oxidative capacity i.e., peroxisome proliferator-activated receptor gamma coactivator-1 (PGC-1alpha) and vascular endothelial growth factor (VEGF), and glycolytic capacity, i.e., phosphofructokinase (PFK), glycogen phosphorylase and synthase, hexokinase, and phosphorylase kinase alpha1, were subsequently analyzed.
  
  
  RESULTS
  Grp UL showed decreased (36%) PGC-1alpha expression, increased (1.5-fold) PFK expression, and a trend toward decreased VEGF post-intervention. Grp UL+RE showed no changes.
  
  
  CONCLUSIONS
  These results suggest that 5 wk unloading reduces skeletal muscle oxidative capacity and increases glycolytic enzyme activity. More importantly, only 12 bouts of high-force, low-volume resistance exercise attenuated these responses. Thus, the current resistance exercise paradigm emphasizing eccentric overload effectively counteracts unwarranted metabolic alterations induced by 5 wk unloading and may, therefore, aid in maintaining skeletal muscle integrity and endurance, and hence astronaut health and fitness during spaceflight.
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Fernandez-Gonzalo
authors.forename: Jose M
authors.initials: JM
authors.lastname: Irimia
authors.forename: Roser
authors.initials: R
authors.lastname: Cusso
authors.forename: Thomas
authors.initials: T
authors.lastname: Gustafsson
authors.forename: Anneli
authors.initials: A
authors.lastname: Linné
authors.forename: Per A
authors.initials: PA
authors.lastname: Tesch
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001707:Biopsy, Needle; D005260:Female; D005786:Gene Expression Regulation; D024981:Glycogen Phosphorylase / Q000235:genetics / Q000378:metabolism; D006006:Glycogen Synthase / Q000235:genetics / Q000378:metabolism; D006593:Hexokinase / Q000235:genetics / Q000378:metabolism; D006801:Humans; D035002:Lower Extremity; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000473:pathology; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D025221:Phosphofructokinases / Q000235:genetics / Q000378:metabolism; D010764:Phosphorylase Kinase / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D055070:Resistance Training; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism; D018474:Weightlessness Simulation
chemical_list: C486497:PPARGC1A protein, human; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D012333:RNA, Messenger; D014157:Transcription Factors; D042461:Vascular Endothelial Growth Factor A; D024981:Glycogen Phosphorylase; D006006:Glycogen Synthase; D025221:Phosphofructokinases; D006593:Hexokinase; D010764:Phosphorylase Kinase