Hi tvr,
Thanks for the question and I hope that I can answer it sufficiently.
1. Treadmills
Certain treadmills with, as you mentioned, elastic cords attached to
the astronaut, are used to simulate the presence of gravity on a
spacecraft. The astronaut is then free to exercise as one would on
earth.
There have been certain innovations on this mechanism, particularly
the pressurized treadmill:
"In this particular design the lower body is completely enclosed in an
airtight chamber. When air is pumped into the chamber, people feel
lighter, and when air is sucked out they feel heavier. By “making
astronauts feel heavier in the weightlessness of space the chamber
could prevent deconditioning, or loss of strength”. The negative
pressure in the chamber makes the astronauts “feel heavier and
increases their endurance as they workout.” (Julianne Remington,
HealthSurfing.com). "
http://www.ibiblio.org/astrobiology/index.php?page=adapt04
2. Space boots:
Space boots have been designed such that the feet feel as if a
reaction force is being applied to them, hence activating all the
balancing muscles in the feet and lower body:
"Chuck Layne, an associate professor at the Univerisy of Houston,
designed special boots that use pneumatic pressure to the feet to
simulate the feeling of standing on a floor. The pressure applied to
the feet stimulates muscles in the legs, the idea being that this
stimulation is akin to a muscle contraction and would thus slow the
rate of muscle atrophy. The invention has been tested by cosmonauts on
Mir and the results look promising, although the technology is still
under development."
http://www.ibiblio.org/astrobiology/index.php?page=adapt04
3. Drugs
Certain drugs are used by astronautical teams to counter the effect of
muscle atrophy and bone demineralisation. However, there are certain
issues related to these drugs:
"However, there are a few important considerations that must be taken
into account when dealing with pharmaceuticals. For one thing, it is
difficult to determine if a drug will affect the body in space in the
manner it affects the body on Earth. Because major physiological
changes occur in zero-gravity, there is no guarantee that the body
will react to a drug the same way as on Earth. If research conducted
on people who fly airplanes at high altitudes is any indication, drugs
can produce drastically different effects when administered in
different environments."
http://www.ibiblio.org/astrobiology/index.php?page=adapt04
In particular, amino acids are said to be a useful supplement for
preventing muscle loss:
"Scientists at the National Space Biomedical Research Institute have
used enforced bed rest as a model for both space travel and
medically-caused immobility. They find that if subjects who rest in
bed for 28 days are given supplements of amino acids, the rates of
muscle loss are much reduced. The amino acids are the building blocks
of protein and blood tests show how they are taken up by the body to
build new muscle."
http://www.healthandage.com/PHome/gm=20!gid1=2071
4. Diet
"While nutrition alone does not cure the conditions that develop as a
result of zero-gravity, it certainly helps alleviate the severity of
those conditions. It is essential that astronauts maintain a healthy
diet despite their decreased appetites (which are characteristic of
people living in microgravity - NASA has found that astronauts eat and
drink as much as 70 percent less in space). The body needs all the
assistance it can get when fighting infections with a depressed immune
system. Good nutrition provides that assistance."
http://www.ibiblio.org/astrobiology/index.php?page=adapt04
5. "Gene Therapy"
There is also an interesting process labelled 'gene therapy', that
introduces a certain protein, named "IGF-1", into a muscle to
stimulate muscle growth and maintanence, thereby minimising atrophy
(this is interesting and worth a look!):
http://spaceresearch.nasa.gov/research_projects/spacebiology_12-2001_lite.html
Here is a more detailed and non-space related analysis:
http://www.cs.hmc.edu/~rmcknigh/projects/bio52-project2/bio52-aging-info.html
6. Electrical stimulation
There has been research into electrically stimulating the muscles, and
hence exercising them (have you seen advertisements for the
'abtronic'?!). This is a possibility for space travel:
"Previous studies have proven the efficacy of Neuromuscular Electrical
Stimulation (NMES) protocols that stimulate muscle through skin
surface electrodes in order to cause muscle contraction. Although NMES
protocols have proven useful in minimizing muscle atrophy, they cause
discomfort to those undergoing treatment and are impractical for
spaceflight. CSA's Operational Space Medicine (OSM) group conducted a
study to investigate a new type of electrical muscle stimulation
called Therapeutic Electrical Stimulation (TES)."
http://www.space.gc.ca/asc/eng/csa_sectors/human_pre/cao/osm_ems.asp
Although it is apparently 'impractical for spaceflight', it is still a
large part of microgravity remedies - the "Manned Spaceflight and
Microgravity" site seems to deem it worthy:
http://www.spaceflight.esa.int/file.cfm?filename=utildestpems
7. Pre-flight training
Finally, and quite obviously, "astronauts undergo extensive preflight
physical training, building endurance and strength to minimize the
effects of muscle atrophy."
http://paperairplane.mit.edu/16.423J/Space/SBE/muscle/muscle_bckgrnd_ug.html
Please let me know if I can be of any further assistance. Thank you
for this very interesting question!
Thanks again!
bobby_d
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