Spaceflight crew members often suffer from space flight deconditioning including neurovestibular
disorientation, cardiovascular deconditioning, myatrophy, and bone mineral loss. Several
countermeasures have been introduced, but no single measure has been proved to be
effective as the countermeasure. We have constructed the short arm centrifuge with
ergometer with the radius of 1.4 m because the available space in international space station was reported to the inside
of the cylinder with the diameter of 2.8 m. Subjects were required to lay down with supine position. Their legs were raised
up to 70 cm high, and there, cycling pedals, which was fixed at the level of leg rotation,
were stepped during centrifuge. G-level of 1.4 G with ergometric exercise of 60 W was loaded in the countermeasure group while control group were requested to lie
down without exercise. Prescription of countermeasure was set at the AG load with
exercise from the 1.4 G at the heart level and 4 – 5 G at the foot level, with ergometric exercise of 60 W in cumulated 30 min per day. Head-down bedrest of −6° was required to 6 subjects as an analogue of microgravity exposure with 2300 kcal/day, and the same amount of water drinking as the urine volume was recommended
in the next day. Before and after the bed-rest, several measurements were applied
to assess neurovestibular, cardiovascular, musculoskeletal, and bone metabolism, and
bedrest studies were carried out comparing the countermeasure and control groups.
Orthostatic tolerance was evaluated by determining the anti-G score, measuring the
time to the endpoint of centrifugation from 1.0 to 2.0 G with 0.2 steps, and summing up the products of G level and time in seconds. Tilt
test was performed to examine the responses to the orthostasis with recording of muscle
sympathetic nerve activity by microneurography. Several hormones including renin,
angiotensin II, and aldosterone as well as vasopressin were determined. Muscle dimension
was determined by applying the MRI to measure the cross-sectional area of quadriceps
femoris and gastrocnemius. Muscle function was tested by measuring maximal forces.
Bone metabolism was assessed by measuring the urinary and blood levels of bone metabolism
including deoxypyridinoline and other markers. As the results, centrifuge-induced
artificial gravity with exercise has been provided significant difference from the
control. We concluded artificial gravity is effective in mitigating spaceflight deconditioning
in humans.
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© 2015 Published by Elsevier Inc.