Elastic energy in locomotion: Spring-mass vs. poly-articulated models.
The human is often modeled as a Poly-Articulated Model (PAM) with rigid segments while some authors use a Spring Mass Model (SMM) for modeling locomotion. These two models are considered independent, and the objective of this study was to link them in order to enlighten the origin of the elasticity in locomotion. Using the characteristics of the two models, a theoretical relationship demonstrates that the variation of elastic energy of the SMM equals the variation of the internal kinetic energy minus internal forces work of the PAM. This theoretical relationship was experimentally investigated among 19 healthy participants walking and running on a treadmill. The results showed that the equality is verified except during the double support phase at 0.56ms(-1), at high walking speeds (1.67 and 2.22ms(-1)) or during the aerial phase of running. The formal relationship showed that the global stiffness of the SMM is directly related to the work of the internal forces of the PAM, and thus, to the characteristics of the musculoskeletal system. It also showed the relevance of taking into account the participation of each joint in the global stiffness. Finally, the coordination of internal forces work to produce a global stiffness may be considered as a new criterion of movement optimization for clinical purposes or motion planning for humanoid robots.
Research Center on Animal Cognition (CRCA), Center for Integrative Biology (CBI), Toulouse University, CNRS, UPS, France. Electronic address: pierre.moretto@univ-tlse3.fr.
Pierre
P
Moretto
Université de Toulouse, UPS, 118 route de Narbonne, F-31062 Toulouse Cedex 9, France.
David
D
Villeger
Université de Toulouse, UPS, 118 route de Narbonne, F-31062 Toulouse Cedex 9, France.
Antony
A
Costes
CNRS, LAAS, 7 avenue du colonel Roche, F-31077 Toulouse, France; Université de Toulouse, UPS, LAAS, F-31077 Toulouse, France.
Bruno
B
Watier
D001696:Biomechanical Phenomena / Q000502:physiology; D005684:Gait / Q000502:physiology*; D006801:Humans; D007700:Kinetics; D008124:Locomotion / Q000502:physiology*; D008297:Male; D008954:Models, Biological; D000072797:Walking Speed / Q000502:physiology; D055815:Young Adult
Elastic energy; Energy transfers; Human gait; Mechanical energy theorem; Work of internal forces