From Simple to Complex Models: Gaits as Oscillations

In nature, humans and animals move in ways that allow them to achieve energetically economical motion over a large range of velocities. In particular, researchers have shown that legged animals use multiple gaits in order to minimize their cost of transport (COT; the amount of energy used per distance traveled [1], [2]). For example, humans transition from walking to running [3], and horses transition from walking, to trotting, to galloping [4] as their current gait becomes uneconomical. In addition, Hoyt and Taylor found that when horses were allowed to self-select their velocities within a particular gait, they chose to move at the energetic minimum. Similar results have been obtained in a number of optimization studies that were conducted with conceptual dynamic models [5], [6], [7], showing that energetic efficiency can be achieved by using different modes of locomotion.