Is the caudofemoralis longus muscle the primary driver of crocodilian propulsion?

SMSU Event Center BC

The caudofemoralis longus (CFL) muscle is assumed to play an important role in crocodilian terrestrial locomotion. Earlier electromyographic studies of the American alligator hind limb musculature found that the CFL muscle is active during the stance phase, and thus acts as the primary retractor and medial rotator of the thigh. Our project uses a surgical approach to test this hypothesis in twelve alligator hatchlings. We performed unilateral tenotomy (severing the distal tendons) on the right CFL muscle to render it nonfunctional, while the contralateral (left) side was shamoperated. Animals were allowed to recover and grow for three months, at which point surface markers were placed on their hind limb joints (ankle, knee, hip). We filmed their locomotor behaviour at 1000Hz using three high-speed video cameras to allow for track markers and reconstruct hind limb posture kinematics in 3D. Using ProAnalyst software, we analysed differences joint angles, as well as hip height and stride length at constant-speed strides during level walking. Ground reaction forces by the hind foot were measured using a force plate flush with the walkway surface and analysed with the help of IGOR. Preliminary data suggest no significant differences in hind limb posture between the tenotomised and control sides. This leads us to suggest that the CFL muscle is not a primary driver of crocodilian terrestrial locomotion