Figure 2
From: Foot force direction control during a pedaling task in individuals post-stroke
Two coordinate systems were defined: the pedal coordinates system and the global coordinates system. (A) The pedal reference system was originally set to allow the FN (normal force perpendicular to pedal) and FS (shear force parallel to pedal) exerted on the pedal to be defined, with negative normal force directed downwards (FN), and negative shear force (FS) directed towards the front of the pedal. Then, a 2-D rotation matrix was used to transfer the data initially obtained with respect to the pedal reference system to the global coordinate system (B), to allow the forces perpendicular (FZ) and parallel (FX) to the horizontal ground and the PedAng orientation relative to the horizontal ground to be computed, with negative vertical forces (FZ) directed downwards and negative horizontal forces (FX) directed towards the front of the cycle ergometer. Pedal angle position (PedAng) was expressed with respect to horizontal.