As you can imagine, this natural position for humans but unnatural position for
quadrupeds tends to wind up and artificially tighten the muscles, tendons, and ligaments in the area of the hip.
When people build robots, whether it is a humanoid, a
quadruped or a fish, they
tend to create very complex mechanisms, and this complexity often works against them by creating multiple points of potential failure, Valdivia y Alvarado says.