Pedalling in space as a countermeasure to microgravity deconditioning.
A system consisting of two mechanically coupled counter rotating bicycles, moving on the inner wall of a cylindrical space module, is proposed to prevent microgravity deconditioning. The two pedalling subjects generate a centrifugal acceleration vector (ac) simulating gravity. This last depends on the peripheral velocity (v) and on the radius of gyration (R): ac = v2/R. Since R is constant and equal to the inner radius of the space module, any desired value of ac can be achieved by selecting the appropriate v value. The corresponding mechanical (w) and metabolic (VO2) powers can then be calculated on the basis of the biomechanical and anthropometric characteristics of the system and subjects. It is shown that if R = 2 m, in order to attain ac = 1 g at the feet, v = 4.5 m s-1, w = 60 W and VO2 = 1.2 litres min-1. However if R = 6 m, then v = 7.8 m s-1, w = 140 W and VO2 = 3 litres min-1. The average arterial pressures prevailing at the head and feet levels in the two above conditions can also be calculated as 95, 150 and 80, 170 mmHg, respectively for a mean arterial pressure of 100 mmHg at the aortic bulbus. In conclusion, by selecting appropriately the radial dimensions of the space module in order to minimize: (1) vestibular disturbances, (2) head to feet centrifugal acceleration gradients and (3) manufacturing costs, it may be possible to combine exercise and simulated gravity, with no need for additional external power.
Antonutto
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G
Institute of Biology, School of Medicine, Udine, Italy.
Capelli
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C
Di Prampero
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PE
D000337:Aerospace Medicine; D001642:Bicycling / Q000502:physiology*; D001696:Biomechanical Phenomena; D001794:Blood Pressure / Q000502:physiology; D018493:Cardiovascular Deconditioning / Q000502:physiology*; D002320:Cardiovascular Physiological Phenomena; D002498:Centrifugation / Q000295:instrumentation; D005081:Exercise Therapy / Q000379:methods*; D018470:Gravity, Altered; D006801:Humans; D010101:Oxygen Consumption; D013026:Space Flight / Q000295:instrumentation*; D014893:Weightlessness / Q000009:adverse effects*; D018544:Weightlessness Countermeasures