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EXPERIMENT INFORMATION

Relationship of Long-Term Electromyographic Activity and Hormonal Function to Muscle Atrophy and Performance (284036)
Principal Investigator
Research Area:
Muscle physiology
Species Studied
Scientific Name: Homo sapiens Species: Human

Description
OBJECTIVES:
The muscular system and the neural control elements of the neuromuscular system are significantly affected by space flight. Rapid adjustments in motor control are required just after launch and throughout the mission in order to function effectively in microgravity. Degradation in skeletal muscle function associated with space flight may be caused, at least partially, by altered motor functions. This experiment was designed to examine questions related to 1) the control of movement under a variety of conditions, 2) a human's ability to adapt movement skills to perform successfully under rapidly changing gravitational conditions, 3) the physiological adjustments occurring in these different conditions that may be responsible for alterations in movement precision and limitations in physical performance during postflight and recovery procedures, and 4) the physiological mechanisms that trigger neuromuscular adaptations to space flight.

The investigation was designed to determine the relationship between the electromyographic (EMG) activity of the calf and elbow muscles and the level to which their functional integrity can be maintained in prolonged space flight. The selected muscles to be tested were located in the calf of the right leg and the upper right arm: the ankle dorsiflexor (m. tibialis anterior, TA) and plantar flexor (m. gastrocnemius medialis, GM, and m. soleus, SO) of the calf, the elbow flexor (m. biceps brachii, BB) and elbow extensor (m. triceps brachii, TB) in the arm.

The specific objectives of the experiment were:
1. To determine daily activity of the musculus soleus (SO), m. gastrocnemius medialis (GM), m. tibialis anterior (TA), m. biceps brachii (BB), and m. triceps brachii (TB) before, during and after space flight.
2. To determine the EMG-torque relationship for the SO, GM, TA, BB and TB muscles during maximal and submaximal efforts before, during and after flight.
3. To determine the changes in motor control of the ankle, elbow and hand-grip.
4. To determine the fatigability of the ankle plantar flexors (SO and GM) before, during and after flight.
5. To determine the blood plasma levels of immunoreactive growth hormone (IRGH), insulin-like growth factor (IGF1), growth hormone carrier protein, thyroxine (T4), triiodothyronine (T3), testosterone, insulin, and cortisol before, during, and after flight.
6. To determine the bioassayable growth hormone (GH) response to exercise before, during and after space flight.
7. To determine the relationship between plasma hormone levels and the decrease in plantar flexor torque associated with muscle fatigue.


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Publications
Edgerton R. Neuromuscular Adaptation to Actual and Simulated Weightlessness. Advances in Space Biology and Medicine. Vol. 4.1994;4:33-67.[pubmed.gov]

McCall GE, Goulet C, Roy RR, Grindeland RE, Boorman GI, Bigbee AJ, Hodgson JA, Greenisen MC, Edgerton VR. Spaceflight suppresses exercise-induced release of bioassayable growth hormone. Journal of Applied Physiology. 1999 September; 87(3):1207-12. [pubmed.gov]

Keywords
Carbon dioxide (CO2)
Heart rate
Muscle fibers
Oxygen consumption
Reaction time

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Data Information
Data Availability
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Parameters
Adenosine triphosphatase ATPase in muscle fiber
Angular velocity
Body mass
Carbon dioxide concentration expired gas
Carbon dioxide CO2 concentration in expired gas
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Mission/Study Information
Mission Launch/Start Date Landing/End Date Duration
STS-78 06/20/1996 07/07/1996 17 days

Additional Information
Managing NASA Center
Johnson Space Center (JSC)
Responsible NASA Representative
Johnson Space Center LSDA Office
Project Manager: Pamela A. Bieri
Institutional Support
National Aeronautics and Space Administration (NASA)
Alternate Experiment Name
MCIM
E036
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