Aim: 

Cycling on appropriately constructed tracks may help maintaining physical fitness and cardiovascular conditioning of crews living in permanently manned bases on the Moon or Mars.

Methods: 

Cycling along a curved path induces a centrifugal acceleration which depends on the ground speed (s) and on the radius of curvature (R): (a_c = s²/R). The vectorial sum of ac and the acceleration of gravity (g) lies in the plane which includes the centre of mass of the system and the points of contact between wheels and terrain. The resulting vector (g') can be calculated by simple geometry: g' = [radic](g_M² + a_c²), where g_M (=1.62 m s^-2 or 3.72 m s^-2) is the acceleration of gravity on the Moon or Mars. So, a cyclist riding a bicycle on a circular track generates a force acting in the head to feet direction mimicking the effects of gravity.

Results: 

For s between 10 to 20 m s^-1 (36 to 72 km h^-1) and R from 50 to 100 m, g' ranges from 0.19 to 0.83 of the Earth gravity on the Moon and from 0.43 to 0.90 on Mars. To be operational on the Moon or on Mars, these tracks must be enclosed in appropriate structures within which the air is maintained at a predetermined pressure and temperature. The speeds necessary to achieve sufficiently large values of the vector simulating gravity (g') can be achieved without surpassing the subjects' maximal O₂ consumption only if the air pressure and temperature in the track tunnel are maintained at about 250 mm Hg (33.3 kPa) and 20° C. Thus, the gas contained in the "track tunnel" should be appropriately enriched in O₂, so as to bring its inspiratory fraction to about 0.50. Finally the angles of g' with the vertical, in the range of speed and radiuses mentioned above will vary from 10° to 78.6°, thus showing that the curved parts of the track should be appropriately constructed.

Conclusion: 

This state of affairs is presumed to counteract, on the one side muscle atrophy, on the other cardiovascular deconditioning that may result from long duration permanence in low gravity bases.