exercises and wearing the Lower Extremity Monitoring Suite (LEMS) system. Results show the
LEMS is capable of providing valid and useful biomechanical information on long-term exercise
activities aboard the ISS (Cavanaugh 2009). Normal daily activity ground-reaction forces on the
feet are measured for each crew member for 4 days prior to going to space, and approximately
4-7 days’ worth of data are recorded while the subject is performing daily activities on the ISS.
Experimental data show that foot forces, based on direct in-shoe force measurements, are
greatly reduced, upward to nearly half in some cases,
for the same activity as on Earth. These mechanical
loading reductions on weight-bearing bones are used
to correlate the rate of bone loss of the most affected
areas of the skeleton. The results demonstrate exercise
countermeasures with TVIS, CEVIS, and iRED are not
adequate in preventing significant bone degradation
over long-duration spaceflights. It is concluded that the
lighter amount of force applied to bones and muscles
during exercise and daily activities aboard the ISS plays
a crucial role in the reduction of Bone Mineral Density
(BMD) (Cavanaugh 2010). Additional results showed
that foot loads were reduced by at least two-thirds
while performing resistive exercises on these
equipment with the exception of the CEVIS at its
highest setting. It is concluded that the TVIS, CEVIS, and
iRED, as designed, were not generating enough
resistive loads equal to that on Earth, and the need for
greater loading should be addressed for upgrades and
the next generation of exercise equipment for the ISS
(Genc 2010). Precise measurement of the forces
exerted by the muscles and bones in microgravity
provides a means to quantify the relationship between
force reduction and the rate of atrophy of the
musculoskeletal system. Researchers are optimistic
that the hypothesis of minimum-loading stimulus, in
terms of exercise repetition and the amount of force
being applied, can be confirmed and the threshold to
maintain fitness can be accurately pinpointed. Already,
the latest generation of exercise equipment with
improved mechanical loading, individually tailored exercise programs, and crew-friendly setup
and maintenance is being implemented on the ISS. The Combined Operational Load Bearing
External Resistance Treadmill (COLBERT) and Advance Resistive Exercise Device (ARED) are
actively collecting data while giving crew members the high-intensity workouts they need in
order to remain healthy over the course of their mission.
ISS012E18576 – Astronaut William S. (Bill)
McArthur, Expedition 12 commander and
NASA space station science officer, uses
the Cycle Ergometer with Vibration Isolation
System (CEVIS) while participating in the
Foot/Ground Reaction Forces During
Spaceflight (Foot) experiment in the Destiny
laboratory of the International Space Station
(ISS). McArthur wore the specially
instrumented Lower Extremity Monitoring
Suit (LEMS), cycling tights outfitted with
sensors, during the experiment.