Two-thirds power law in human locomotion: Role of ground contact forces

Yuri P. Ivanenko, Renato Grasso, Velio Macellari, Francesco Lacquaniti

Research output: Contribution to journalArticlepeer-review


Are there general rules for the generation of curvilinear motion of the end-effector? Form and kinematics of the arm trajectory are typically inter-related. A relationship between velocity and curvature of the endpoint path has been previously described and quantified as the two-thirds power law. Here we show that the two-thirds power law holds also for the foot trajectory (during the swing phase) in human locomotion for a wide range of walking speeds and gravitational loads, but air-stepping. In air-stepping, it was violated systematically. The results suggest that the power law represents a general constrain of biological motion, may be attributed to both mechanical and neural factors and can depend on natural interactions with external environment.

Original languageEnglish
Pages (from-to)1171-1174
Number of pages4
Issue number9
Publication statusPublished - Jul 2 2002


  • Air-stepping
  • Body weight unloading
  • Contact forces
  • Foot trajectory
  • Two-thirds power law
  • Walking

ASJC Scopus subject areas

  • Neuroscience(all)


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