Femur-bending properties as influenced by gravity: II. Ultimate load, moment, and stress for 3-G mice.

Material strength as approximated from bending studies of fresh femurs grew during 1 to 8 weeks of hypergravity at rates which were not measurably affected, even though the animal's body growth was measurably slower. As a result, femurs could support greater ultimate loads, moments, and stresses when compared to control bones of comparable rotational moments of their cross-sectional areas. Chronic centrifugation simulated 3.1 G for 45 male. Swiss Webster mice compared to 37 control animals. Effects were most noticeable after the first week of exposure and for younger animals. Effect were only about 50% that noted in comparable treatment of rats. This suggests that four times more mice than rats may be necessary for space-experiments designed to test the effects of weightlessness.