Understanding and predicting the effects of spaceflight on the
human body can be challenging because humans have not spent enough
time in microgravity to accurately determine the risk of health
problems associated with exploration missions.
NASA planners developing concepts for longer, more physically demanding
missions need to better understand how human physiology is altered
during spaceflight. Such knowledge will allow them to establish
meaningful mission requirements for health and safety. To
this end, the NASA Human Research Program Human Health Countermeasures
Element chartered the Digital Astronaut Project. Led out of
the Glenn Research Center, and in partnership with the Johnson Space
Center, the Digital Astronaut Project is an effort to utilize deterministic
simulations of human physiological function to answer targeted questions
about changes associated with the microgravity environment.
The project is currently working in several areas, one of which
is quantifying the effects of exercise. In spite of attempts
to use exercise to counteract losses in bone density and muscle
tone during spaceflight, these problems continue, with longer flights
generally correlating with greater loss. In an attempt to
quantify the response to exercise, project personnel created a model
of the Advanced Resistive Exercise Device (ARED) that astronauts
currently use on the International Space Station (ISS). In
tandem with that effort, the team also developed models of humans
performing ARED exercises. The team is currently integrating
both models, with a goal of quantifying muscle force and joint torque
produced by the exercise. Data produced by these simulations
will allow exercise physiologists to design better exercise prescriptions
for the astronauts.
In conjunction with the exercise models, project personnel are
also developing computational simulations of bone remodeling and
muscle function. In the case of bone, no current analytic
formulation is able to describe the effects of muscle stress, strain,
and gravitational loading on bone remodeling. Bone tissue
is actually in a perpetual state of flux, with old tissue constantly
being destroyed and new tissue created. In healthy individuals
living in earth’s gravity field, these effects balance. In
microgravity, however, tissue formation in weight bearing regions
of the skeleton slows dramatically, leading to bone loss. These
simulations should provide key insight into how the turnover process
proceeds in microgravity, as well as providing recommendations for
the daily amount of loading required to counteract the effect.
While muscle models are more developed, computational tools generally
do not accurately predict microgravity effects, which means that
the team must alter the foundation of those tools so that they can
faithfully reflect the effects of microgravity.
Finally, many astronauts return from space with vision changes,
presumably caused by an increase in cerebral-spinal fluid pressure. This
pressure change is likely a result of the well-known head ward fluid
shift that occurs as soon as humans enter microgravity. Project
personnel are currently conducting a survey to determine what computational
tools and data sets are available to simulate this problem. When
that survey is complete, the team will use a combination of existing
and custom tools to develop a simulation quantifing this effect.
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Advanced
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Deadlift |
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Single Leg |
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