Concurrent Exercise on a Gravity-Independent Device during Simulated Microgravity

• Published in: Medicine and science in sports and exercise 2015-05, Vol.47 (5), p.990-1000
• Main Authors: COTTER, JOSHUA A, YU, ALVIN, HADDAD, FADIA, KREITENBERG, ARTHUR, BAKER, MICHAEL J, TESCH, PER A, BALDWIN, KENNETH M, CAIOZZO, VINCENT J, ADAMS, GREGORY R
• Format: Article
• Language: English
• Subjects: Aged; Atrophy; Exercise - physiology; Female; Humans; Male; Middle Aged; Muscle Fatigue - physiology; Muscle Strength - physiology; Muscle, Skeletal - growth & development; Muscle, Skeletal - pathology; Muscle, Skeletal - physiology; Oxygen Consumption; Physical Education and Training - methods; Resistance Training; RNA, Messenger - metabolism; Weightlessness Simulation - instrumentation; Young Adult
• ISSN: 0195-9131; 1530-0315
• DOI: 10.1249/MSS.0000000000000483

PURPOSEThe 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). METHODSNineteen subjects (10 males and 9 females; 21.0 ± 2.5 yr, 65.4 ± 12.2 kg) were separated into two groups1) 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. RESULTSAerobic 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). CONCLUSIONThese 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.