Effect of Prolonged Space Flight on Human Skeletal Muscle (Biopsy) - 01.09.14
Science Objectives for Everyone
The Biopsy researchers take calf muscle biopsies of crew members before and after their stay aboard the International Space Station (ISS). This allows scientists to begin developing an in-space countermeasure exercise program aimed at keeping muscles at their peak performance during long missions in space.
Science Results for Everyone
Maintaining strong muscles is a big enough challenge on Earth. It is much harder to do in space where there is no gravity. Calf muscles biopsies before flight and after a six months mission on the ISS show that even when crew members did aerobic exercise five hours a week and resistance exercise three to six days per week, muscle volume and peak power both still decrease significantly. Overall, the data suggest that current exercise countermeasures are not enough. The addition of a second treadmill and the Advanced Resistive Exercise Device (ARED) along with more rigorous exercise regiment are giving good results in preventing muscle loss and preserving overall muscle health.
Johnson Space Center, Human Research Program, Houston, TX, United States
Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)
Human Exploration and Operations Mission Directorate (HEOMD)
ISS Expedition Duration:
June 2002 - October 2005
Previous ISS Missions
The Extended Duration Orbiter Medical Project measured astronauts' health after shuttle flights scheduled between 1989 and 1995. This provided some short-term data regarding muscles and muscle cells. STS-78 in 1996 was dedicated to muscle research and provided the cellular data for the determination of the effect of short duration flights on muscle. The Russian Mir program studied muscles after long term flight, but these did not provide enough information.
- Preparing for long term human missions into outer space, this experiment aims to characterize the effect of long term space flight on muscle tissue. Overall muscle performance of the multiple calf muscles in ISS crew members will be assessed before and after flight. The performance tests will evaluate the amount of force and power the calf muscles can produce.
- Furthermore, biopsies of two muscles in the calf, the gastrocnemius (largest muscle in the lower leg, able to extend the foot and bend the knee) and the soleus (flat muscle located under the gastrocnemius that flexes the foot), will be used to analyze the health (size, structure and performance) of individual cells within the muscle. Studies will also determine the mechanism of muscle fiber tearing and soreness that occurs postflight.
- Information gathered from this experiment of longer-term space flight will be compared to preexisting data from STS-78 (Life and Microgravity Spacelab Mission) to create a time based model of how muscle reacts to space flight.
It is well established that space flight can result in loss of skeletal muscle mass and strength. This atrophy continues throughout a crew's mission, even if crewmembers adhere to a strict exercise regime. What researchers do not understand, however, are the effects that prolonged stays in microgravity have on skeletal muscles. Biopsy will evaluate changes in calf muscle function over long-duration space flights (30 to 180 days).
For the Biopsy investigation, a specially designed torque velocity dynamometer is used to measure muscle strength before and after flight. Biopsies are also taken from the soleus and gastrocnemius muscles of participants. This allows determination of the cell size and the structural properties of individual fast and slow muscle fibers. Chemical analysis of the biopsies determines muscle fiber structural changes involving myosin, a protein "molecular motor" that drives muscle contractions and cell divisions, enzymes, and substrates. Electron microscopy determines the relationship between thick and thin filament, the amount of myofilament loss, and changes in membrane-associated protein complexes found in skeletal muscle fibers and connective tissue that help the muscle resist stretch-induced damage.
It is well established that muscle mass and strength decrease during space flight. The atrophy of muscles in space can affect not only the performance of astronauts during missions, but it can lead to severe muscle injuries upon return to Earth. Astronauts landing on Mars may be susceptible to muscle injury once they step onto the planet. The exact cellular and biochemical events that produce these losses of mass and strength are not as well understood. Biopsy is the first experiment to tackle the cellular question in long-term space flight. The data from this experiment will be used to illustrate the structural and metabolic changes that occur within individual muscle fiber cells. This experiment will also help create a model that illustrates to what degree muscles deteriorate in space over time, which can be used to predict risks for long term flight. As the mechanisms of muscle deterioration due to space flight become clearer, scientists can pursue new methods to protect muscles for exploration-length missions.
As people age on Earth, muscle tissue tends to loose elasticity. The results of this investigation will provide a better understanding of muscle atrophy in the elderly population on Earth.
The crew's inflight log provides information about their daily exercise and diet, factors that play a role in muscle health. Limited mobility is required on landing day to minimize the stress placed on the calf muscles before the biopsy is performed.
The crew undergoes performance tests on their right calf muscles using the TVD 90, 60, 30, and 15 days before launch. Magnetic Resonance Imaging (MRI) is conducted on L-90 and 30 before the TVD testing. A needle biopsy is taken from the right gastrocnemius and soleus muscles on L-45. Another biopsy is taken on the day the crew returns. Additional TVD performance tests are conducted on the right calf on R+7, 14, 21, and 30, and an MRI is taken of the calf at R+1 and 21.
The aim of this study was to examine muscle physiology and performance of the calf muscles (soleus and gastrocenemius) on astronauts who performed exercise routines during their 6-month stay on ISS. In particular, calf muscle volume, calf muscle performance, and muscle fiber physiology and microanatomy were assessed before and after space flight for these crewmembers who had access to the ISS treadmill, Treadmill with Vibration Isolation System, (TVIS), cycle ergometer, Cycle Ergometer with Vibration Isolation System, (CEVIS) and interim resistive exercise device (IRED). The exercise routine varied among the crewmembers with aerobic exercise performed ~5 hrs/wk at moderate intensity, and resistance exercise performed 3-6 days/wk incorporating multiple lower leg exercises. Despite the exercise programs, overall calf muscle volume significantly decreased by 13¬+2%, peak power decreased significantly by 32%, force-velocity characteristics were reduced significantly to -20 to -29% across the velocity spectrum, and there was a 12-17% shift in myosin heavy chain phenotype with a significant decrease in myosin heavy chain I fiber type along with a redistribution among the faster phenotypes. These data show a reduction in calf muscle mass and performance along with a slow-to-fast fiber type transition in the calf muscles, which are all qualities associated with muscle unloading. Peak force decreased in the Type I soleus muscle, which correlated with a significant decrease in muscle fiber diameter, and inversely correlated with the amount of treadmill running on ISS. This decline in peak force was also associated with an increase in thin filament density of the muscle fiber, which likely contributed to the 21 and 18% decline in maximal velocity in the soleus and gastrocnemius type I fibers, respectively. Taken together, the decrease in muscle performance, (peak power, peak force, peak force-velocity, and maximal velocity), combined with the muscle physiological and anatomical changes, (transition of the slow fiber types into the fast fiber types, increased thin filament density, and decreased fiber diameter and overall muscle volume), indicate that the exercise countermeasures provided on orbit during this study (June 2002 - October 2005) were not sufficient to provide the intensity needed to adequately maintain calf muscle performance and structure. Such a decrease in performance could affect crewmembers’ ability to perform specific tasks, including emergency egress and locomotor tasks upon return to a terrestrial environment, and also render them more susceptible to muscle injury. Since the completion of this study, there has been the addition of a second treadmill, the Combined Operational Load-Bearing External Resistance Treadmill, (COLBERT) to ISS as well as an improved resistance exercise device, the Advanced Resistive Exercise Device (ARED). The authors suggest that a new study be implemented to investigate the efficacy of these new exercise devices on ISS, as they provide high resistance and contractions over a wide range of motion that mimic the range occurring in Earth’s environment (Trappe 2009 and Fitts 2010).
Bagley JR, Murach KA, Trappe SW. Microgravity-Induced Fiber Type Shift in Human Skeletal Muscle.Gravitational and Space Biology. 2012; 26(1): 34-40.
Trappe SW, Costill DL, Gallagher PM, Creer AC, Peters JR, Evans HJ, Riley DA, Fitts RH. Exercise In Space: Human Skeletal Muscle After 6 Months Aboard The International Space Station. Journal of Applied Physiology. 2009 Jan 15; 106: 1159-1168.
Fitts RH, Colloton PA, Trappe SW, Costill DL, Bain JL, Riley DA. Effects of prolonged space flight on human skeletal muscle enzyme and substrate profiles. Journal of Applied Physiology. 2013 September 1; 115(5): 667-679. DOI: 10.1152/japplphysiol.00489.2013. PMID: 23766501.
Fitts RH, Trappe SW, Costill DL, Gallagher PM, Creer AC, Colloton PA, Peters JR, Romatowski JG, Bain JL, Riley DA. Prolonged Space Flight-Induced Alterations in the Structure and Function of Human Skeletal Muscle Fibres. Journal of Physiology. 2010; 588: 3567-3592. DOI: 10.1113/jphysiol.2010.188508.
Ground Based Results Publications
Riley DA, Bain JL, Thompson JL, Fitts RH, Widrick JJ, Trappe SW, Trappe TA, Costill DL. Decreased thin filament density and length in human atrophic soleus muscle fibers after spaceflight. Journal of Applied Physiology. 2000; 88(2): 567-572.
Trappe SW, Trappe TA, Lee GA, Widrick JJ, Costill DL, Fitts RH. Comparison of a space shuttle flight (STS-78) and bed rest on human muscle function. Journal of Applied Physiology. 2001; 91(1): 57-64.
Fitts RH, Riley DA, Widrick JJ. Functional and structural adaptations of skeletal muscle to microgravity. Journal of Experimental Botany. 2001; 204: 3201-3208.
Fitts RH, Romatowski JG, De La Cruz L, Widrick JJ, Desplanches D. Effect of spaceflight on the maximal shortening velocity, morphology, and enzyme profile of fast- and slow-twitch skeletal muscle fibers in rhesus monkeys. Journal of Gravitational Physiology. 2000; 7(1): S37-S38.
Fitts RH. Effects of regular exercise training on skeletal muscle contractile function. American Journal Physical Medicine and Rehabilitation. 2003; 82(4): 320-331.
Riley DA, Bain JL, Thompson JL, Fitts RH, Widrick JJ, Trappe SW, Trappe TA, Costill DL. Thin filament diversity and physiological properties of fast and slow fiber types in astronaut leg muscles. Journal of Applied Physiology. 2002; 92(2): 817-825.
Photograph of a single muscle fiber. Each muscle is composed of thousands of these fibers. Samples of muscle fibers will be extracted and tested as part of the Biopsy experiment. Image courtesy of NASA, Johnson Space Center.
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NASA Image: ISS004E6331 - Expedition 4 Commander Yury Onufrienko exercises on a treadmill in the Zvezda Service Module. Exercise is one of the ways that crew members help counteract muscle atrophy during space flight.
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This photomicrograph shows normal skeletal muscle fibers (above) and atrophied skeletal muscle fibers (below). Note the marked decrease in size of the atrophied skeletal muscle below. Image courtesy of NASA, Johnson Space Center.
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Microscopy image of ATPase and capillary stain of a muscle fiber. Image courtesy of NASA, Johnson Space Center.
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