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

Naomichi Ogihara, Takeo Kikuchi, Yutaro Ishiguro, Haruyuki Makishima, Masato Nakatsukasa

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)


We investigated the planar covariation of lower limb segment elevation angles during bipedal walking in macaques to elucidate the mechanisms underlying the origin and evolution of the planar law in human walking. Two Japanese macaques and four adult humans walking on a treadmill were recorded, and the time course of the elevation angles at the thigh, shank and foot segments relative to the vertical axis were calculated. Our analyses indicated that the planar law also applies to macaque bipedal walking. However, planarity was much lower in macaques, and orientations of the plane differed between the two species because of differences in the foot elevation angle. The human foot is rigidly structured to form a longitudinal arch, whereas the macaque's foot is more flexible and bends at the midtarsal region in the stance phase. This difference in midfoot flexibility between the two species studied was the main source of the difference in the planar law. Thus, the evolution of a stable midfoot in early hominins may have preceded the acquisition of the strong planar intersegmental coordination and possibly facilitated the subsequent emergence of habitual bipedal walking in the human lineage.

Original languageEnglish
Pages (from-to)2181-2190
Number of pages10
JournalJournal of the Royal Society Interface
Issue number74
Publication statusPublished - 2012 Sept 7
Externally publishedYes


  • Foot
  • Kinematics
  • Locomotion
  • Macaca fuscata

ASJC Scopus subject areas

  • Biotechnology
  • Biophysics
  • Bioengineering
  • Biomaterials
  • Biochemistry
  • Biomedical Engineering


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