A Fortran package for the planar analysis of limb intersegmental dynamics from spatial coordinate-time data

Limbs in humans and animals are systems of linked bodies, in which motion of any one part of the linkage exerts forces on the remaining parts. Thus, during natural movements, forces can act on a limb segment even if a segment is not exposed to active muscle forces. Passive reactions arise from forces in tendons, ligaments, and peri-articular tissues, as well as from dynamical limb reactions related to inertial, Coriolis, and centripetal forces. Consequently, limb trajectories are influenced not only by active muscle forces but also by passive, intersegmental forces. For a more complete understanding of movement control, it is important to explain the mechanisms by which active and passive forces are coordinated. To achieve this, an analysis of limb intersegmental dynamics is essential, and here we provide a detailed description of the equations used for the planar analysis of limb intersegmental dynamics from spatial coordinate-time data, as well as the FORTRAN software to perform those calculations.