title: Acute low-intensity cycling with blood-flow restriction has no effect on metabolic signaling in human skeletal muscle compared to traditional exercise.
abstract: OBJECTIVE
  Autophagy is an intracellular degradative system sensitive to hypoxia and exercise-induced perturbations to cellular bioenergetics. We determined the effects of low-intensity endurance-based exercise performed with blood-flow restriction (BFR) on cell signaling adaptive responses regulating autophagy and substrate metabolism in human skeletal muscle.
  
  
  METHODS
  In a randomized cross-over design, nine young, healthy but physically inactive males completed three experimental trials separated by 1 week of recovery consisting of either a resistance exercise bout (REX: 4 × 10 leg press repetitions, 70% 1-RM), endurance exercise (END: 30 min cycling, 70% VO2peak), or low-intensity cycling with BFR (15 min, 40% VO2peak). A resting muscle biopsy was obtained from the vastus lateralis 2 weeks prior to the first exercise trial and 3 h after each exercise bout.
  
  
  RESULTS
  END increased ULK1Ser757phosphorylation above rest and BFR (~37 to 51%, P < 0.05). Following REX, there were significant elevations compared to rest (~348%) and BFR (~973%) for p38γ MAPKThr180/Tyr182phosphorylation (P < 0.05). Parkin content was lower following BFR cycling compared to REX (~20%, P < 0.05). There were no exercise-induced changes in select markers of autophagy following BFR. Genes implicated in substrate metabolism (HK2 and PDK4) were increased above rest (~143 to 338%) and BFR cycling (~212 to 517%) with END (P < 0.001).
  
  
  CONCLUSIONS
  A single bout of low-intensity cycling with BFR is insufficient to induce intracellular "stress" responses (e.g., high rates of substrate turnover and local hypoxia) necessary to activate skeletal muscle autophagy signaling.
authors.affiliation: Mary MacKillop Institute for Health Research, Centre for Exercise and Nutrition, Australian Catholic University, Fitzroy, Melbourne, VIC, 3165, Australia. will.smiles@acu.edu.au.
authors.forename: William J
authors.initials: WJ
authors.lastname: Smiles
authors.affiliation: Faculty of Physical Education, University of Campinas, Campinas, Brazil.
authors.forename: Miguel S
authors.initials: MS
authors.lastname: Conceição
authors.affiliation: Faculty of Physical Education, University of Campinas, Campinas, Brazil.
authors.forename: Guilherme D
authors.initials: GD
authors.lastname: Telles
authors.affiliation: Faculty of Physical Education, University of Campinas, Campinas, Brazil.
authors.forename: Mara P T
authors.initials: MP
authors.lastname: Chacon-Mikahil
authors.affiliation: Faculty of Physical Education, University of Campinas, Campinas, Brazil.
authors.forename: Cláudia R
authors.initials: CR
authors.lastname: Cavaglieri
authors.affiliation: School of Physical Education and Sport, University of São Paulo, São Paulo, Brazil.
authors.forename: Felipe C
authors.initials: FC
authors.lastname: Vechin
authors.affiliation: Laboratory of Neuromuscular Adaptations to Resistance Training, Department of Physical Education, Federal University of São Carlos, São Carlos, Brazil.
authors.forename: Cleiton A
authors.initials: CA
authors.lastname: Libardi
authors.affiliation: Mary MacKillop Institute for Health Research, Centre for Exercise and Nutrition, Australian Catholic University, Fitzroy, Melbourne, VIC, 3165, Australia.|Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, UK.
authors.forename: John A
authors.initials: JA
authors.lastname: Hawley
authors.affiliation: Mary MacKillop Institute for Health Research, Centre for Exercise and Nutrition, Australian Catholic University, Fitzroy, Melbourne, VIC, 3165, Australia.
authors.forename: Donny M
authors.initials: DM
authors.lastname: Camera
mesh_terms: D000293:Adolescent; D000328:Adult; D018592:Cross-Over Studies; D004734:Energy Metabolism / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D010766:Phosphorylation; D012039:Regional Blood Flow / Q000502:physiology*; D055070:Resistance Training / Q000379:methods; D015398:Signal Transduction / Q000502:physiology*; D055815:Young Adult
keywords: Autophagy; Blood-flow restriction; Exercise; Mitophagy