Fact Sheet

Text Size

Effect of Prolonged Space Flight on Human Skeletal Muscle (Biopsy)
02.27.09

Overview | Description | Applications | Operations | Results | Publications | Images

Experiment/Payload Overview

Brief Summary

Effect of Prolonged Space Flight on Human Skeletal Muscle (Biopsy) will examine changes in limb skeletal muscle and cellular mechanisms of muscle degradation are assessed to predict effects of human spaceflight during long duration exploration missions. Tests include calf muscle biopsies, performance tests and MRIs.

Principal Investigator

  • Robert Fitts, Ph.D., Marquette University, Milwaukee, WI

    • Co-Investigator(s)/Collaborator(s)

  • David L. Costill, Ph.D., Ball State University, Muncie, IN
  • Scott W. Trappe, Ph.D., Ball State University, Muncie, IN
  • Danny A. Riley, Ph.D., Medical College of Wisconsin, Milwaukee, WI

    • Payload Developer

    Johnson Space Center, Human Research Program, Houston, TX

    Sponsoring Agency

    National Aeronautics and Space Administration (NASA)

    Expeditions Assigned

    |5|6|7|9|10|11|

    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.

    ^ back to top


    Experiment/Payload Description

    Research Summary

    • 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.

    Description

    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).

    In Biopsy, 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.

    ^ back to top


    Applications

    Space Applications

    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.

    Earth Applications

    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.

    ^ back to top


    Operations

    Operational Requirements

    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.

    Operational Protocols

    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.

    ^ back to top


    Results/More Information

    Preliminary results were presented at the 2004 American Physiological Society Intersociety Meeting: Integrative Biology of Exercise in three abstracts (21.16, 21.17 and 21.19). Summarizing data collected from the first five subjects, microgravity produced a 47% decrease in the peak power of postflight muscle fiber samples compared to preflight muscle fiber samples. This decrease was due to the combined effects of reduced fiber size and a decline in the size of the myofibrils that make up the fiber.

    Further examination of the data collected from the crew indicated that astronauts who performed high treadmill exercise (greater than 200 minutes/week) vs. low treadmill exercise (less than 100 minutes/week) exhibited a smaller decrease in peak power. Astronauts who performed high treadmill exercise showed a 13% decrease compared to a 51% decrease in peak power of astronauts who performed low treadmill exercise. Sample analysis of the muscle fibers indicated that the ratio of myosin and actin proteins in the muscle fibers was not affected by long-duration space flight. Although exercise slowed the onset of atrophy and loss of strength in muscle fibers, a significant amount of muscle volume and strength loss still occurred on long-duration missions.

    Of the exercise countermeasures currently being employed, treadmill exercise appeared the most effective in protecting the calf muscles from loss of strength and atrophy. Final publication is pending the collection of data from the final subjects during Expedition 11.

    ^ back to top


    Related Web Sites

    ^ back to top


    Publications

    Results Publications
    • Trappe S, Costill D, Gallagher PM, Creer A, Peters JR, Evans H, 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.

    ^ back to top


    Related Publications
    • Fitts RH. Effects of regular exercise training on skeletal muscle contractile function. American Journal Physical Medicine and Rehabilitation. ;82(4):320-331. 2003
    • 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. ;7(1):S37-S38. 2000
    • 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. ;88(2):567-572. 2000
    • 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. ;91(1):57-64. 2001
    • Fitts RH, Riley DR, Widrick JJ. Functional and structural adaptations of skeletal muscle to microgravity. Journal of Experimental Biology. ;204:3201-3208. 2001
    • 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. ;92(2):817-825. 2002

    ^ back to top


    Images

    imagePhotograph 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.
    + View Larger Image


    imageNASA 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.
    + View Larger Image


    imageThis 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.
    + View Larger Image


    imageMicroscopy image of ATPase and capillary stain of a muscle fiber. Image courtesy of NASA, Johnson Space Center.
    + View Larger Image


    Information Provided and Updated by the ISS Program Scientist's Office
    › Back To Top