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Randomized Controlled Trial
. 2015 May;47(5):990-1000.
doi: 10.1249/MSS.0000000000000483.

Concurrent exercise on a gravity-independent device during simulated microgravity

Joshua A Cotter  1 , Alvin Yu, Fadia Haddad, Arthur Kreitenberg, Michael J Baker, Per A Tesch, Kenneth M Baldwin, Vincent J Caiozzo, Gregory R Adams
Affiliations
Randomized Controlled Trial

Concurrent exercise on a gravity-independent device during simulated microgravity

Joshua A Cotter et al. Med Sci Sports Exerc. 2015 May.

Abstract

Purpose: 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).

Conclusion: 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.

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Figures

Figure 1
Figure 1
Timeline of the study. BIO, biopsy; ISK, isokinetic testing; 3RM, three repetition max; VO2, peak oxygen consumption; RT, resistance training; AE, aerobic training; ULLS, unilateral lower limb suspension.
Figure 2
Figure 2
M-Med Device configured for squats (A), calf raises (B), and aerobic rowing (C) displaying the start and end position for each movement. Photos courtesy of Lealem Mulugeta, Lead Scientist for NASA's Digital Astronaut Project.
Figure 2
Figure 2
M-Med Device configured for squats (A), calf raises (B), and aerobic rowing (C) displaying the start and end position for each movement. Photos courtesy of Lealem Mulugeta, Lead Scientist for NASA's Digital Astronaut Project.
Figure 2
Figure 2
M-Med Device configured for squats (A), calf raises (B), and aerobic rowing (C) displaying the start and end position for each movement. Photos courtesy of Lealem Mulugeta, Lead Scientist for NASA's Digital Astronaut Project.
Figure 3
Figure 3
Three repetition max values for the leg press (A) and calf raise (B) during ULLS or ULLS+EX. * Significant difference (P < 0.05) or ** (P < 0.01) between PRE and POST conditions.
Figure 3
Figure 3
Three repetition max values for the leg press (A) and calf raise (B) during ULLS or ULLS+EX. * Significant difference (P < 0.05) or ** (P < 0.01) between PRE and POST conditions.
Figure 4
Figure 4
Torque-velocity relationship for the knee extensors (A), knee flexors (B), and ankle plantar flexors (C). Significant group differences were found for the knee extensors and ankle plantar flexors only. Fatigue testing for the knee extensors is presented for ULLS (D) and ULLS+EX (E). * Significant difference (P < 0.05).
Figure 4
Figure 4
Torque-velocity relationship for the knee extensors (A), knee flexors (B), and ankle plantar flexors (C). Significant group differences were found for the knee extensors and ankle plantar flexors only. Fatigue testing for the knee extensors is presented for ULLS (D) and ULLS+EX (E). * Significant difference (P < 0.05).
Figure 4
Figure 4
Torque-velocity relationship for the knee extensors (A), knee flexors (B), and ankle plantar flexors (C). Significant group differences were found for the knee extensors and ankle plantar flexors only. Fatigue testing for the knee extensors is presented for ULLS (D) and ULLS+EX (E). * Significant difference (P < 0.05).
Figure 4
Figure 4
Torque-velocity relationship for the knee extensors (A), knee flexors (B), and ankle plantar flexors (C). Significant group differences were found for the knee extensors and ankle plantar flexors only. Fatigue testing for the knee extensors is presented for ULLS (D) and ULLS+EX (E). * Significant difference (P < 0.05).
Figure 4
Figure 4
Torque-velocity relationship for the knee extensors (A), knee flexors (B), and ankle plantar flexors (C). Significant group differences were found for the knee extensors and ankle plantar flexors only. Fatigue testing for the knee extensors is presented for ULLS (D) and ULLS+EX (E). * Significant difference (P < 0.05).
Figure 5
Figure 5
Myosin heavy chain mRNA expression as a % change from PRE values for the vastus lateralis (A) and soleus (B). * Significant difference (P < 0.05) or ** (P < 0.01) between ULLS and ULLS+EX.
Figure 5
Figure 5
Myosin heavy chain mRNA expression as a % change from PRE values for the vastus lateralis (A) and soleus (B). * Significant difference (P < 0.05) or ** (P < 0.01) between ULLS and ULLS+EX.
Figure 6
Figure 6
mRNA expression as a % change from PRE values for the vastus lateralis (A) and soleus (B) for selected markers of growth/atrophy and sarcomeric structural proteins. * Significant difference (P < 0.05) between ULLS and ULLS+EX.
Figure 6
Figure 6
mRNA expression as a % change from PRE values for the vastus lateralis (A) and soleus (B) for selected markers of growth/atrophy and sarcomeric structural proteins. * Significant difference (P < 0.05) between ULLS and ULLS+EX.
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