[email protected].kr Model based balance & gait analysis Effective leg stiffness increases with speed to maximize propulsion energy Dynamics & Energetics of Human Walking Seyoung Kim and Sukyung Park, “Leg stiffness increases with speed to modulate gait frequency and propulsion energy”, Journal of Biomechanics, Vol.44(7): 1253-1258, 2011 Human Gait Research Seyoung Kim, PhD
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Effective leg stiffness increases with speed to maximize propulsion energy Dynamics & Energetics of Human Walking Seyoung Kim and Sukyung Park, “Leg stiffness.
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Effective leg stiffness increases with speed to maximize propulsion energy
Dynamics & Energetics of Human Walking
Seyoung Kim and Sukyung Park, “Leg stiffness increases with speed to modu-late gait frequency and propulsion energy”, Journal of Biomechanics, Vol.44(7): 1253-1258, 2011
• Spring and damping constants from an optimiza-tion (Matlab®) that minimized the least square error between the GRF data and the model simu-lation over one step gait cycle, which consists of double and single support phases.
• Humans emulate spring-like leg mechanics, and modu-late the apparent stiffness at a given walking speed.
Conclusion
• Leg stiffness increases with speed to modulate gait frequency and propulsion energy.
• Application: • Quantifying parameter changes among different walking condi-
tion and/or subject groups• Gait performance assessment for the elderly or patients• Development of walking assist device• Multi-joint stiffness to whole leg stiffness
• The compliant walking model does not require an energy input mechanism to maintain steady walk-ing. However, human walking requires active pos-itive and negative muscle work [ Donelan et al., 2002 ].
• Multi-joint stiffness characteristics were lumped into whole-leg stiffness. Thus, the compliant walk-ing model does not specify how changes in leg stiffness might be attributed to changes at each joint.
• Funds– Postural control study was supported by a Basic Research Fund
of the Korea Institute of Machinery and Materials, the second stage of the Brain Korea 21 Project, and a National Institute on Aging.
– Walking research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Tech-nology (#2010-0013306) and the Unmanned Technology Re-search Center (UTRC) at the Korea Advanced Institute of Sci-ence and Technology (KAIST), originally funded by DAPA, ADD.
• Collaborators– Fay B. Horak (Oregon Health & Science University)– Patricia Carlson-Kuhta (Oregon Health & Science University)– Chris G. Atkeson (Carnegie Mellon University)
The oscillatory behavior of the CoM facilitates mechanical energy balance between push-off
and heel strike
Dynamics & Energetics of Human Walking
Seyoung Kim and Sukyung Park, “The oscillatory behavior of the CoM facilitates mechanical en-ergy balance between push-off and heel strike”, Journal of Biomechanics, Vol.44(7): 1253-1258, 2011
• The least costly gait is achieved when the push-off propulsion fully compensates for the collision loss during the double support phase, during which the redirection of the center of mass (CoM) occurs [ Jin and Park 2011; Kuo 2002 ].
• The duration of the CoM redirection can also be defined based on changes in work or velocity, and those durations are greater than that of the dou-ble support phase.
• The purpose of this study was to examine whether different definitions of the step-to-step transition (SST) would affect the mechanical en-ergy balance between push-off and heel strike during gait.
• The observed robustness of energetic optimality may be attributable to the seemingly symmetric oscillatory behavior of the CoM during the step-to-step transition. – Recent studies have described the motion of the CoM of
the body during the gait cycle as the oscillation of the inertia on a compliant leg.
– Due to the intrinsic symmetry of the mechanical power of an oscillatory mechanism around the minimum and maximum heights of the CoM, the mechanical powers of the mass before and after the mid point of the double support phase are approximated to be the same in mag-nitude but opposite in sign, showing energetic symme-try.
• Funds– This research was supported by the Basic Science Re-
search Program through the National Research Founda-tion of Korea (NRF) funded by the Ministry of Education, Science and Technology (#2010-0013306) and the Un-manned Technology Research Center (UTRC) at the Ko-rea Advanced Institute of Science and Technology (KAIST), originally funded by DAPA, ADD.