The dynamics and energetics of locomotion depend on the number of propulsive legs

Although land animals can move in many different ways, most terrestrial creatures use legs to crawl, scuttle, walk and run about. Leg-propelled animals such as mammals, insects, spiders or centipedes, feature a wealth of differently designed locomotor apparatuses and a wide range of leg numbers. In order to cover distances with energy efficiency, many terrestrial animals exploit mechanisms enabling energy recovery. Such mechanisms can comprise repeated interconversion of kinetic and potential energy due to vertical oscillations of the body’s centre of mass or the use of elastic energy stores. They typically occur in bouncing gaits—as found in running bipeds or trotting quadrupedal and hexapedal animals.