DIFFERENTIAL FOREPAW AND HINDPAW FORCE TRANSMISSION IN THE WALKING RAT

Previous studies suggest that the stance phase of the rat stride is in itiated by a soft contact period when the forepaw may engage in tactil e sampling of the terrain. However, no ground reaction force measureme nts have yet been made during rat locomotion. In the dog and other qua drupeds a brief or nonexistent soft contact phase is observed. Therefo re, forces and pressures exerted via fore and hindpaws have been measu red in the spontaneously walking rat. These indicate that, while the h indpaw vertical reaction forces are temporally similar to those in the dog, those transmitted via the forepaw are not. At average walking ve locities the forepaw soft contact time is some 4 times longer than tha t of the hindpaw, with values of 207 +/- 25 ms and 52 +/- 12.2 ms (mea n +/- 1 SEM) respectively. These data are consistent with the idea of forepaw useage to provide tactile information of the terrain during a prolonged initial soft contact phase, while the hindpaw transmits most of the early vertical ground reaction forces.