RUBENSON, J*; LLOYD, D.G.; BESIER, T.F.; HELIAMS, D.B.; FOURNIER, P.A.; Univ. Western Australia: 3D kinematics and kinetics of running in the ostrich (Struthio camelus)

While several studies have enhanced our understanding of the mechanics of avian bipedalism, many have focused only on locomotor kinematics and/or whole body dynamics or have been limited to 2D analysis. The present study examines both the 3D joint kinematics and kinetics of running in the largest avian bipedal species, the ostrich. A 5 segment, 3D-anatomical model of the ostrich lower limb was developed from cadaver specimens. High-speed video and force data were collected from 3 ostriches running (3.0-4.0 m/s) on a rubber-topped runway, where marker clusters placed on the limb segments were used in conjunction with the anatomical model to compute 3D joint angles. Inverse dynamic analysis was used to calculate flexion/extension (FE), adduction/abduction (AA), varus/valgus (VV; at the knee) and internal/external (IE) joint moments and powers. As was expected, the greatest motion at all joints occurs in FE. However, a substantial frontal plane component occurs during the re-orientation of the foot (toe) position during the swing-phase. The majority of mechanical work during stance occurs at the metatarso-phalangeal joint (64%), whereas the majority of the work of the swing-phase occurs at the knee (45%) and ankle (42%). Although mechanical work and power occurs predominantly in FE the same is not true for the joint moments. A very large valgus moment at the knee (~250 Nm) and abduction moment at the ankle (~200 Nm) are required during mid-stance and are due not only to limb posture but also to the geometry of the joints. Although muscle forces can contribute to these non-FE moments they are likely also produced by joint articular and ligament forces, signifying the importance of passive joint structures in providing stability and protecting against injury.