Meeting Abstract
The kinematic flexibility of frog hindlimbs enables multiple locomotor modes within a single species. Prior work has extensively explored maximum performance capacity in frogs; however, the mechanisms modulating performance within locomotor modes remain unclear. We measured how Kassina maculata modulates jump trajectory from horizontal to nearly vertical. Specifically, how do 3D motions of leg segments coordinate to move the center of mass (COM) upwards and forwards? How do joint rotations modulate jump angle? High-speed video was used to quantify 3D joint angles and their respective rotation axis vectors. Inverse kinematics was used to determine how hip, knee and ankle rotations contribute to components of COM motion. We found two possible mechanisms for increasing takeoff angle: Firstly, greater knee and ankle excursion increased shank adduction, elevating the COM. Secondly, during the steepest jumps the body rotated rapidly backwards to redirect the COM velocity. This rotation was not caused by pelvic angle extension, but rather by kinematic transmission from leg segments via reorientation of the joint rotation axes. We propose that K. maculata uses proximal leg retraction as the principal kinematic drive while dynamically tuning jump trajectory by knee and ankle joint modulation. We will further explore direct causes for joint-level control using forward dynamic musculoskeletal modelling.
