Dynamical determinants of different spine movements and gait speeds in rotary and transverse gallops

Abstract

Quadruped gallop is categorized into two types: rotary and transverse. While the 11 rotary gallop involves two types of flight with different spine movements, the transverse gallop 12 involves only one type of flight. The rotary gallop can achieve faster locomotion than the 13 transverse gallop. To clarify these mechanisms from a dynamic viewpoint, we developed a simple 14 model and derived periodic solutions by focusing on cheetahs and horses. The solutions gave a 15 criterion to determine the flight type: while the ground reaction force does not change the 16 direction of the spine movement for the rotary gallop, it changes for the transverse gallop, which 17 was verified with the help of animal data. Furthermore, the criterion provided the mechanism by 18 which the rotary gallop achieves higher-speed than the transverse gallop based on the flight 19 duration. These findings improve our understanding of the mechanisms underlying different 20 gaits that animals use. 21 22 65 2018; Fujiki et al., 2018; Aoi et al., 2019; Toeda et al., 2019). Because the essential contribution 66 of the legs can be represented by springs, the spring-loaded inverted pendulum (SLIP) model was 67 developed to investigate animal locomotion mechanism from a dynamic viewpoint, particularly 68 for human running and walking (Tanase et al., 2015) to clarify the 72 common and unique principles between animal gaits. Recently, the SLIP model has been further 73 improved to investigate the dynamic roles of spine movement in quadruped running (Cao and 74 Poulakakis, 2013; Pouya et al., 2017; Wang et al., 2017; Kamimura et al., 2015, 2018). However, 75 the mechanisms underlying the different flight phases between the rotary and transverse gallops 76 380 Alexander M. Why mammals gallop. Integr Comp Biol. 1988; 28(1):237-245.