This paper studies a 2D. spring-loaded inverted pendulum (SLIP) passive dynamic biped with two degrees of freedom (stance leg only) to find the existence of symmetric periodic walking and jogging gaits. These gaits are differentiated by vertical ground reaction force (vGRF) patterns. The double-support phase is considered to be instantaneous. https://www.chiggate.com/3m-speedglas-9002nc-welding-helmet-fashion/