title: Exercise Responses to Gravity-Independent Flywheel Aerobic and Resistance Training.
abstract: BACKGROUND
  Although several exercise systems have been developed to mitigate the physiological deconditioning that occurs in microgravity, few have the capacity to positively impact multiple physiological systems and still meet the volume/mass requirements needed for missions beyond low Earth orbit. The purpose of this study was to test the gravity-independent Multi-Mode Exercise Device (M-MED) for both resistance (RE) and aerobic (AE) training stimuli.
  
  
  METHODS
  Eight men and nine women (mean age 22.0 ± 0.4 yr) completed 5 wk of training on the M-MED: RE 4 × 7 squats 2 d/wk, and AE 4 × 4-min rowing bouts at ∼90% Vo2max 3 d/wk. Pre- and post-training data collection included an aerobic capacity test, MR imaging, strength testing, and vastus lateralis muscle biopsy.
  
  
  RESULTS
  Vo2max increased 8%, 3RM strength 18%, and quadriceps femoris cross-sectional area (CSA) 10%. Knee extensor strength increased at all isokinetic speeds tested. Subjects also demonstrated improved fatigue resistance in knee extension. At the cellular and molecular level, the biopsy revealed increases in mixed myofiber CSA (13%), citrate synthase activity (26%), total RNA concentration (24%), IGF-I mRNA (77%), and Type IIa myosin heavy chain (MHC) mRNA (8%), and a concomitant decrease in Type IIx MHC mRNA (-23%). None of the changes were gender-specific.
  
  
  CONCLUSIONS
  Both the functional outcomes and biomarker changes indicate that a very low volume of M-MED exercise results in robust adaptation in the cardiovascular and musculoskeletal systems. The M-MED has the potential to provide a wide range of countermeasure exercises and should be considered for testing in ground-based spaceflight simulation.
authors.affiliation: University of California Irvine, Irvine, CA, USA.
authors.forename: Tomasz
authors.initials: T
authors.lastname: Owerkowicz
authors.forename: Joshua A
authors.initials: JA
authors.lastname: Cotter
authors.forename: Fadia
authors.initials: F
authors.lastname: Haddad
authors.forename: Alvin M
authors.initials: AM
authors.lastname: Yu
authors.forename: Marinelle L
authors.initials: ML
authors.lastname: Camilon
authors.forename: Theresa N
authors.initials: TN
authors.lastname: Hoang
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Jimenez
authors.forename: Arthur
authors.initials: A
authors.lastname: Kreitenberg
authors.forename: Per A
authors.initials: PA
authors.lastname: Tesch
authors.forename: Vincent J
authors.initials: VJ
authors.lastname: Caiozzo
authors.forename: Gregory R
authors.initials: GR
authors.lastname: Adams
mesh_terms: D000222:Adaptation, Physiological; D002320:Cardiovascular Physiological Phenomena; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D053580:Muscle Strength; D009142:Musculoskeletal Physiological Phenomena; D010807:Physical Endurance / Q000502:physiology; D055070:Resistance Training; D018474:Weightlessness Simulation; D055815:Young Adult