The role of cross-sectional geometry, curvature, and limb posture in maintaining equal safety factors: a computed tomography study

摘要: The limb bones of an elephant are considered to experience similar peak locomotory stresses as a shrew. "Safety factors" maintained across the entire range body masses through combination robusticity long bones, postural variation, and modification gait. relative contributions these variables remain uncertain. To test role shape change, we undertook X-ray tomographic scans leg 60 species mammals birds, extracted geometric properties. maximum resistible forces could withstand before yield under compressive, bending, torsional loads were calculated using standard engineering equations incorporating curvature. Positive allometric scaling cross-sectional properties with mass was insufficient prevent negative allometry bending (F(b) ) force (F(t) (and hence decreasing safety factors) in mammalian (femur F(b) ∞M(b) (0.76) , F(t) (0.80) ; tibia avian hindlimbs (tibiotarsus (0.88) (0.89) exception femoral . minimum angle from horizontal bone must be held while maintaining given factor combined compressive increases M(b) femur. Postural erectness is shown effective means achieving stress similarity mammals. behavior femur discussed light unusual posture kinematics.