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Myotendinous and Neuromuscular Adaptation to Long-term Spaceflight: Determinants and Time Courses. (Sarcolab)
Principal Investigator
Research Area:
Muscle physiology
Species Studied
Scientific Name: Homo sapiens Species: Human

Exposure to actual and simulated microgravity is known to lead to loss of muscle mass, function and motor control. The first goal of this project is to investigate the myotendinous structural and functional determinants of this phenomenon using an in vivo and in vitro approach. Whole skeletal muscle in vivo (plantarflexors) and in vitro on isolated muscles fibers (from soleus muscle) which are most affected by microgravity will be studied for humans exposed to long-term spaceflight. The second goal of this project is to characterize reflex excitability of the dis-used muscles.

It is known that the force per cross-sectional area (F/CSA) as well as the force of isolated muscle fibers decreases following actual and simulated space flight. Recent evidence shows that a loss of muscle strength may not only be related to neural drive and muscular changes, but also to tendon and extracellular matrix alterations affecting the mechanical output of the muscle and its ability to transduce mechanical signals into chemical processes driving protein synthesis. Sarcolab is trying to investigate this phenomenon further, using an in vivo and in vitro approach, by studying the plantar flexors in vivo, and isolated muscle fibers of the soleus in vitro.

The contractile characteristics of the plantar flexors are studied during static (isometric contractions at different joint angles) and dynamic (isokinetic contractions at different angular velocities) contractions performed on the MARES dynamometer. Muscle architectural features, such as fiber fascicle length and pennation angle are assessed using ultrasound imaging and Magnetic Resonance Imaging (MRI). Tendon mechanical properties such as stiffness and hysteresis are assessed by ultrasound imaging and during a slow ramp isometric contraction.

Furthermore, Sarcolab evaluates the changes in the elastic properties of the musculo-tendionous system by measuring ankle flexibility (range of motion), quick-release tests and sinusoidal perturbations and the stretch reflex. For this purpose, EMG electrodes will be placed on the tested leg during maximal and submaximal isometric contraction. This will also provide information about muscle fatigability.

Before and after the flight a biopsy sample of the Soleus will be obtained to study single muscle fiber properties. The force will be related to the myosin concentration to clarify whether the loss of specific force is related to myosin and whether it occurs both in slow and fast muscle fibers. Additional tests include maximum shortening velocity to determine if the loss of velocity is caused by changes in the function of myosin itself or if other muscle components are involved. For further analysis of the involved mechanisms the quantity and type of costameric proteins is determined using two different analysis methods.

Combining the results obtained on whole muscle, single fibers and tendon, will clarify whether the decrease in F/CSA of locomotor muscles following spaceflight is due to a) an impairment of the contractile capacity of the muscle tissue itself, b) a change in tendon mechanical properties, c) modifications in muscle architecture and/or d) alterations in the extracellular matrix.

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Muscle fibers
Muscle proteins

Data Information
Data Availability
Archiving in progress. Data is not yet available for this experiment.

A micro RNA (miRNA), profiles
Activation capacity
Adenosine triphosphate (ATP) consumption
Adipokines, pro-anti inflammatory
Ankle, flexibility
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Mission/Study Information
Mission Launch/Start Date Landing/End Date Duration
Expedition 35 03/15/2013 05/13/2013 58 days
Expedition 36 05/13/2013 09/10/2013 166 days
Expedition 37 09/10/2013 11/10/2013 61 days
Expedition 41 09/10/2014 11/09/2014 29 days
Expedition 42 11/10/2014 03/11/2015 121 days

Additional Information
Managing NASA Center
Johnson Space Center (JSC)
Responsible NASA Representative
Johnson Space Center LSDA Office
Project Manager: Jessica Keune
Institutional Support
European Space Agency (ESA)
Proposal Source