Myocellular Responses to Concurrent Flywheel Training during 70 Days of Bed Rest

Murach, Kevin A.; Minchev, Kiril; Grosicki, Gregory J.; Lavin, Kaleen M.; Perkins, Ryan; Ryder, Jeffrey W.; Scott, Jessica; Ploutz‐Snyder, Lori L.; Trappe, Todd A.; Trappe, Scott

doi:10.1249/mss.0000000000001620

Cited by 14 publications

(15 citation statements)

References 30 publications

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“…Type 1 and 2 muscle fibers demonstrate differential hypertrophic plasticity under a wide variety conditions in humans ( Luden et al, 2010 ; Murach et al, 2014 , 2018b ), and myonuclear domain flexibility during hypertrophy accordingly seems to differ by fiber type. Our laboratory ( Fry et al, 2014b ) and others ( Herman-Montemayor et al, 2015 ; Damas et al, 2018 ) showed that the myonuclear domain of human Type 2 muscle fibers, which comprise ∼50% of muscle fibers in most muscles, is highly flexible.…”

Section: Evidence For Myonuclear Domain Flexibility During Hypertrophmentioning

confidence: 99%

Myonuclear Domain Flexibility Challenges Rigid Assumptions on Satellite Cell Contribution to Skeletal Muscle Fiber Hypertrophy

et al. 2018

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Satellite cell-mediated myonuclear accretion is thought to be required for skeletal muscle fiber hypertrophy, and even drive hypertrophy by preceding growth. Recent studies in humans and rodents provide evidence that challenge this axiom. Specifically, Type 2 muscle fibers reliably demonstrate a substantial capacity to hypertrophy in the absence of myonuclear accretion, challenging the notion of a tightly regulated myonuclear domain (i.e., area that each myonucleus transcriptionally governs). In fact, a “myonuclear domain ceiling”, or upper limit of transcriptional output per nucleus to support hypertrophy, has yet to be identified. Satellite cells respond to muscle damage, and also play an important role in extracellular matrix remodeling during loading-induced hypertrophy. We postulate that robust satellite cell activation and proliferation in response to mechanical loading is largely for these purposes. Future work will aim to elucidate the mechanisms by which Type 2 fibers can hypertrophy without additional myonuclei, the extent to which Type 1 fibers can grow without myonuclear accretion, and whether a true myonuclear domain ceiling exists.

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Section: Evidence For Myonuclear Domain Flexibility During Hypertrophmentioning

confidence: 99%

Myonuclear Domain Flexibility Challenges Rigid Assumptions on Satellite Cell Contribution to Skeletal Muscle Fiber Hypertrophy

et al. 2018

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“…The SPRINT protocol was based on previous work into exercise and muscle fiber function in those experiencing bed rest (Trappe et al., 2004, 2008). The SPRINT protocol is notably different to the previous μG exercise prescriptions and is characterized by alternative days of strength and continuous aerobic exercise and interval type aerobic exercise (Murach et al., 2018). It is apparent that those preparing for and experiencing human space flight are required to train concurrently for the development and maintenance of strength and aerobic qualities.…”

Section: Exercise Countermeasures During Human Space Flight and Micromentioning

confidence: 99%

“…Furthermore, there is no evidence to suggest that continuous or intermittent rowing results in any inference characteristics. In fact, recent work has indicated that resistance training using a gravity-independent flywheel and aerobic training via continuous and intermittent rowing was able to preserve several key muscle characteristics during 70 days of bed rest (Murach et al., 2018). It should also be noted that Murach et al.…”

Section: Program Variablesmentioning

confidence: 99%

“…In fact, recent work has indicated that resistance training using a gravity-independent flywheel and aerobic training via continuous and intermittent rowing was able to preserve several key muscle characteristics during 70 days of bed rest (Murach et al., 2018). It should also be noted that Murach et al. (2018) observed a combination of eccentric strength training and intermittent rowing successfully preserved muscular integrity of the soleus.…”

Section: Program Variablesmentioning

confidence: 99%

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Optimization of Exercise Countermeasures for Human Space Flight: Operational Considerations for Concurrent Strength and Aerobic Training

2019

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The physiological challenges presented by space flight and in microgravity (μG) environments are well documented. μG environments can result in declines muscle mass, contractile strength, and functional capabilities. Previous work has focused on exercise countermeasures designed to attenuate the negative effects of μG on skeletal muscle structure, function, and contractile strength and aerobic fitness parameters. Exposure to μG environments influences both strength and aerobic type physical qualities. As such, the current exercise recommendations for those experiencing μG involve a combination of strength and aerobic training or “concurrent training.” Concurrent training strategies can result in development and maintenance of both strength and aerobic capabilities. However, terrestrial research has indicated that if concurrent training strategies are implemented inappropriately, strength development can be inhibited. Previous work has also demonstrated that the aforementioned inhibition of strength development is dependent on the frequency of aerobic training, modality of aerobic training, the relief period between strength and aerobic training, and the intra-session sequencing of strength and aerobic training. While time constraints and feasibility are important considerations for exercise strategies in μG, certain considerations could be made when prescribing concurrent strength and aerobic training to those experiencing human space flight. If strength and aerobic exercise must be performed in close proximity, strength should precede aerobic stimulus. Eccentric strength training methods should be considered to increase mechanical load and reduce metabolic cost. For aerobic capacity, maintenance cycle and/or rowing-based high-intensity intermittent training (HIIT) should be considered and cycle ergometry and/or rowing may be preferable to treadmill running.

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“…Both groups performed the same exercise prescription with the same intensity. The goal of comparing the two exercise groups was to evaluate the efficacy of a small exercise device that combines aerobic and resistive exercise for use on future exploration spaceflight vehicles (flywheel) compared to the suite of exercise devices available on the International Space Station (ISS) today (traditional) [ 37 ]. Therefore, one exercise group used traditional equipment similar to that found on the ISS and the other used a single compact flywheel rowing and resistance exercise device.…”

Section: Methodsmentioning

confidence: 99%

Exercise effects on bed rest-induced brain changes

et al. 2018

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PurposeSpaceflight negatively affects sensorimotor behavior; exercise mitigates some of these effects. Head down tilt bed rest (HDBR) induces body unloading and fluid shifts, and is often used to investigate spaceflight effects. Here, we examined whether exercise mitigates effects of 70 days HDBR on the brain and if fitness and brain changes with HDBR are related.MethodsHDBR subjects were randomized to no-exercise (n = 5) or traditional aerobic and resistance exercise (n = 5). Additionally, a flywheel exercise group was included (n = 8). Exercise protocols for exercise groups were similar in intensity, therefore these groups were pooled in statistical analyses. Pre and post-HDBR MRI (structure and structural/functional connectivity) and physical fitness measures (lower body strength, muscle cross sectional area, VO2 max, body composition) were collected. Voxel-wise permutation analyses were used to test group differences in brain changes, and their associations with fitness changes.ResultsComparisons of exercisers to controls revealed that exercise led to smaller fitness deterioration with HDBR but did not affect brain volume or connectivity. Group comparisons showed that exercise modulated post-HDBR recovery of brain connectivity in somatosensory regions. Posthoc analysis showed that this was related to functional connectivity decrease with HDBR in non-exercisers but not in exercisers. Correlational analyses between fitness and brain changes showed that fitness decreases were associated with functional connectivity and volumetric increases (all r >.74), potentially reflecting compensation. Modest brain changes or even decreases in connectivity and volume were observed in subjects who maintained or showed small fitness gains. These results did not survive Bonferroni correction, but can be considered meaningful because of the large effect sizes.ConclusionExercise performed during HDBR mitigates declines in fitness and strength. Associations between fitness and brain connectivity and volume changes, although unadjusted for multiple comparisons in this small sample, suggest that supine exercise reduces compensatory HDBR-induced brain changes.

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Myocellular Responses to Concurrent Flywheel Training during 70 Days of Bed Rest

Abstract: The integrated resistance and aerobic training protocol on a device maintains several key myocellular characteristics during prolonged unloading, but further refinement of the exercise approach to fully protect the SOL is warranted.

Cited by 14 publications

References 30 publications

Myonuclear Domain Flexibility Challenges Rigid Assumptions on Satellite Cell Contribution to Skeletal Muscle Fiber Hypertrophy

Myonuclear Domain Flexibility Challenges Rigid Assumptions on Satellite Cell Contribution to Skeletal Muscle Fiber Hypertrophy

Optimization of Exercise Countermeasures for Human Space Flight: Operational Considerations for Concurrent Strength and Aerobic Training

Exercise effects on bed rest-induced brain changes

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