Forward dynamic simulation of bipedal walking in the Japanese macaque: Investigation of causal relationships among limb kinematics, speed, and energetics of bipedal locomotion in a nonhuman primate

Abstract

Japanese macaques that have been trained for monkey performances exhibit a remarkable ability to walk bipedally. In this study, we dynamically reconstructed bipedal walking of the Japanese macaque to investigate causal relationships among limb kinematics, speed, and energetics, with a view to understanding the mechanisms underlying the evolution of human bipedalism. We constructed a two-dimensional macaque musculoskeletal model consisting of nine rigid links and eight principal muscles. To generate locomotion, we used a trajectory-tracking control law, the reference trajectories of which were obtained experimentally. Using this framework, we evaluated the effects of changes in cycle duration and gait kinematics on locomotor efficiency. The energetic cost of locomotion was estimated based on the calculation of mechanical energy generated by muscles. Our results demonstrated that the mass-specific metabolic cost of transport decreased as speed increased in bipedal walking of the Japanese macaque. Furthermore, the cost of transport in bipedal walking was reduced when vertical displacement of the hip joint was virtually modified in the simulation to be more humanlike. Human vertical fluctuations in the body's center of mass actually contributed to energy savings via an inverted pendulum mechanism.

Common formation mechanism of basin of attraction for bipedal walking models by saddle hyperbolicity and hybrid dynamics

“…• Bipedal walking is a typical hybrid system due to foot contact and foot off • The center of mass of the human body moves like an inverted pendulum (the inverted pendulum mechanism [9,14])…”

“…This means that humans produce efficient walking through the pendular exchange of potential and kinetic energy while conserving mechanical energy [3][4][5]. This is called the inverted pendulum mechanism [9,14], and inverted pendulums have been widely used as the simplest model for the movement of the center of mass, when investigating the underlying mechanism in human walking [1,7,8,11,12].…”

Planar covariation of limb elevation angles during bipedal walking in the Japanese macaque

“…Bipedal walking of non-human primates has been well studied in the field of physical anthropology [15][16][17][18][19][20][21][22][23][24][25][26][27][28] and, among these, we have examined bipedal walking in bipedally trained Japanese macaques (Macaca fuscata) [29][30][31][32][33][34][35][36]. The acquisition of bipedal walking in an inherently quadrupedal primate could be regarded as a modern analogue for the evolution of bipedal walking, thereby offering an interesting model for understanding the evolution of human bipedalism.…”

Standing on the shoulders of apes: Analyzing the form and function of the hominoid scapula using geometric morphometrics and finite element analysis

“…Nowadays it is possible to produce scientifically accurate virtual reconstructions of primates (Zollikofer and Leon, ; Sellers et al, ; Ogihara et al, ; Weber and Bookstein, ). Technological advances in 3D imaging allow the generation of virtual models based on skeletal morphology and comparative soft tissue data obtained from the literature.…”