EFFECT OF PROLONGED SPACEFLIGHT ON HUMAN SKELETAL MUSCLE (BIOPSY)
Research Area: Bone and Muscle Physiology
Expeditions: 5-7 and 9-11
Principal Investigator(s): ● Robert H. Fitts, PhD, Marquette University, Milwaukee,
Wisconsin
RESEARCH OBJECTIVES
Biopsy examines calf muscle samples of crew members before and after their stay aboard the
International Space Station (ISS) to study muscle adaptation to weightlessness. This
investigation helps to develop exercise program aimed
at keeping muscles at their peak performance during
long-duration space missions.
EARTH BENEFITS
As people age on Earth, muscle tissue tends to lose
elasticity. The results of this research provide a better
understanding of muscle atrophy in the elderly
population on Earth.SPACE BENEFITS
It is well established that muscle mass and strength
decrease during spaceflight. The atrophy of muscles in
space affects not only the performance of crew
members during missions, but 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 spaceflight. The data from this
experiment are used to illustrate the structural and metabolic changes that occur within
individual muscle fiber cells. This experiment also helps to 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 during spaceflight become clearer,
scientists can pursue new methods to protect muscles for long missions.
RESULTS
This study examined calf muscle physiology and performance of the astronauts who completed
exercise routines on various exercise systems during their 6-month stay on the ISS. Specifically,
calf muscle volume, calf muscle performance, and muscle fiber physiology and microanatomy
were assessed before and after spaceflight. Data showed a reduction in calf muscle mass and
performance along with a slow-to-fast fiber type transition in the calf muscles. The decrease in
muscle performance, combined with muscle physiological and anatomical changes (transition
of the slow fiber types into the fast fiber types, increased thin filament density, and decreased
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. NASA
image.