ABSTRACT: Various types of functions that robotic can carry out are reviewed, namely; walking, jumping, leaping, hopping, and running. General and specific features for each type of function are discussed towards pinpointing how to design proper paths. A simulation model for the leg linkage by an equivalent spring is proposed. The model′s steady function is achieved by a chain of repeated cycles consisting of compatible segmented paths. Thus, an air segment is a symmetric portion of a whole standard sinusoidal curve. Two numerical case studies reveal that no matter how the legs steadily function, the motion performed by contributing parts has to be based on three considerations. First, the path of the hip joint w.r.t. horizontal ground level should be well stated. Second, the base motion of the supporting leg axle is close to pure rotation about toe/ground adhesion point. Third, the relative contraction of the leg radius expresses the counterpart joints shaping angles and control moments relative to the leg axis. In addition, an appropriate motion designed for the other leg determines the specific type of the intended output function. The output function properly proceeds as long as the other leg is given the accurate time to recover its incoming landing profile.