Fig. 3. Empirical and modeled vertical ground reaction forces and displacements of the center of mass. (A) Empirical vertical ground reaction force data for Cheirogaleus medius (body mass=180 g) while ambling at 1.2 m s^-1along a 28 mm diameter pole. Thin lines correspond to the individual limb forces and the thick line is the total (i.e. summed) force. The black thin line represents the left fore- and hindlimb forces obtained from sequential, overlapping footfalls on a pole segment connected to a force platform. The left limb forces were replicated a half-cycle out of phase to obtain right limb forces (gray lines). Individual limb forces were modeled following the mathematical model used (McNeill Alexander and Jayes, 1978) using empirical values for body mass and duty factor. (B) Model forces reconstructed for a whole stride for a diagonality of 63% (i.e. the diagonality used by C. medius in A). (C) Model forces reconstructed for a diagonality of 50% (i.e. a running trot). Horizontal bars below the reaction forces represent the footfall patterns (RH=right hindlimb, LF=left forelimb, LH=left hindlimb, and RF=right forelimb). The vertical displacements of the center of mass corresponding to the vertical force data in A-C are shown in D-F, respectively. Displacement data were calculated following published methods (Cavagna, 1975).