title: Concurrent exercise on a gravity-independent device during simulated microgravity.
abstract: OBJECTIVE
  The objective of this study is to examine the effect of a high-intensity concurrent training program using a single gravity-independent device on maintaining skeletal muscle function and aerobic capacity during short-term unilateral lower limb suspension (ULLS).
  
  
  METHODS
  Nineteen subjects (10 males and 9 females; 21.0 ± 2.5 yr, 65.4 ± 12.2 kg) were separated into two groups: 1) 10-d ULLS only (n = 9) and 2) 10-d ULLS plus aerobic and resistance training (ULLS + EX, n = 10). Exercise was performed on a single gravity-independent Multi-Mode Exercise Device (M-MED) with alternating days of high-intensity interval aerobic training and maximal exertion resistance training.
  
  
  RESULTS
  Aerobic capacity increased by 7% in ULLS + EX (P < 0.05). Knee extensor and ankle plantar flexor three-repetition maximum increased in the ULLS + EX group (P < 0.05), but this change was only different from ULLS in the plantar flexors (P < 0.05). Peak torque levels decreased with ULLS but were increased for the knee extensors and attenuated for the ankle plantar flexors with ULLS + EX (P < 0.05). A shift toward type IIx myosin heavy-chain mRNA occurred with ULLS and was reversed with ULLS + EX in the vastus lateralis (P < 0.05) but not the soleus. Myostatin and atrogin increased with ULLS in both the vastus lateralis and soleus, but this change was mitigated with ULLS + EX only in the vastus lateralis (P = 0.0551 for myostatin, P < 0.05 for atrogin). Citrate synthase was decreased in the soleus during ULLS but was increased with ULLS + EX (P < 0.05).
  
  
  CONCLUSIONS
  These results indicate that an M-MED class countermeasure device appears to be effective at mitigating the deconditioning effects of microgravity simulated during a modified ULLS protocol.
authors.affiliation: 1Department of Physiology and Biophysics, University of California, Irvine, CA; 2Department of Orthopaedic Surgery, University of California, Irvine, CA; 3Department of Kinesiology, California State University, Long Beach, CA; and 4Department of Physiology and Pharmacology, Karolinska Institute, Stockholm, SWEDEN.
authors.forename: Joshua A
authors.initials: JA
authors.lastname: Cotter
authors.forename: Alvin
authors.initials: A
authors.lastname: Yu
authors.forename: Fadia
authors.initials: F
authors.lastname: Haddad
authors.forename: Arthur
authors.initials: A
authors.lastname: Kreitenberg
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Baker
authors.forename: Per A
authors.initials: PA
authors.lastname: Tesch
authors.forename: Kenneth M
authors.initials: KM
authors.lastname: Baldwin
authors.forename: Vincent J
authors.initials: VJ
authors.lastname: Caiozzo
authors.forename: Gregory R
authors.initials: GR
authors.lastname: Adams
mesh_terms: D000368:Aged; D001284:Atrophy; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018763:Muscle Fatigue / Q000502:physiology; D053580:Muscle Strength / Q000502:physiology; D018482:Muscle, Skeletal / Q000254:growth & development / Q000473:pathology / Q000502:physiology*; D010101:Oxygen Consumption; D010806:Physical Education and Training / Q000379:methods*; D012333:RNA, Messenger / Q000378:metabolism; D055070:Resistance Training; D018474:Weightlessness Simulation / Q000295:instrumentation*; D055815:Young Adult
chemical_list: D012333:RNA, Messenger