Steve Collins, Steven H. Collins, S.H. Collins, Dynamics, Mechanics, Locomotion, passive-dynamics, Simulation, amputees, unilateral, bilateral, below-knee, foot prosthesis, amputee, foot prostheses, metabolic energy, Energy Use, Reducing Energy Use, A Prosthetic Foot That, Reduces Energy Use, human, anthropomorphic, neuromuscular, musculoskeletal, systems, simple models, Intelligent Prosthetic Systems, Intelligent Mechatronic Systems, Mechanical Engineering, University of Michigan, Art Kuo, nonholonomic booboobechu.
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Lower limb amputees require more metabolic energy to walk than intact individuals. Amputees expend 20-30% more metabolic power to walk at the same speed as able-bodied individuals, and compensate by preferring a slower speed to cover the same distance (Molen 1973, Colborne et al 1992, Herbert et al 1994). This increased energy demand for walking limits mobility, and is especially limiting for individuals who suffer from vascular disease, who are the majority of amputees in the U.S. Vascular patients have reduced aerobic capacity, making even slow walking a more energetically demanding task (McGavock et al 2004). |
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Metabolic power can be thought of as a measure of "how hard" the body is working. It is a measure of the chemical energy that a person's body uses, or metabolizes, to do work at a cellular level. In particular, muscles doing mechanical work use a lot of metabolic energy. We think that people try to walk in a way that keeps energy requirements as low as possible while still completing the task, the so called "principle of least effort". |
   Subjects undergoing metabolic data collection while walking on a treadmill. Click images to enlarge. |
To measure metabolic power used by the body, we use a VO2 (volume of oxygen) analysis method. With some assumptions about the chemical reactions the body uses (Brockway 1987), we can estimate how much chemical power it is consuming by measuring the rate at which oxygen is removed from, and carbon dioxide added to, the air. Subjects breathe through an apparatus that measures flow rate and gas concentrations as they perform the task of interest. Most of our testing is done in the Human Neuromechanics Laboratory facilities, in collaboration with Mark Taylor and Ammanath Peethambaran of the U of M Orthotics and Prosthetics Center. |
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Commercial prosthetic feet do not currently reduce the metabolic cost of walking, though many have been designed for that very purpose (Phillips 1985 & 1989, Poggi et al 1987, Robinson et al 1993). Many such feet use passive mechanisms to provide articulation, cushioning, and elastic energy return. Recent intelligent knees, which improve gait by actively controlling braking of the knee, have resulted in a 5-10% decrease in energy cost for walking (Buckley et al 1997). In comparison, prosthetic feet of any type, such as energy-storing feet, have not shown consistent energy improvements (Lehmann et al 1993a & b, Torburn et al 1995, Gailey et al 1997, Thomas et al 2000). One reason is that the elastic mechanisms in energy-storing feet have a static stiffness, yet must simultaneously satisfy numerous objectives that require different stiffnesses. A more efficient gait is therefore difficult to achieve with a passive prosthesis. |
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Advanced designs for prosthetic feet are a practical application of passive-dynamic walking research. Passive-dynamic simulations and robots predict that the primary source of energy loss, and thus energy use, in walking will be the redirection of the velocity of the body at the step-to-step transition, a prediction borne out in clinical studies (Donelan et al 2002). Therefore, the mechanical interactions of the prosthetic foot during double support can have a large impact on the metabolic energy requirements of an amputee; some of the mechanical work used in redirecting the center of mass of the individual could be done by the device and not by muscular work. In other words, we should be able to build feet that make it easier to walk. |
    Left: The first prototype. Center: Foot prosthesis simulator tests. Right: A recent CESR prototype on an amputee. |
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Our current designs for energy-saving foot prostheses focus on using active control to improve the mechanics of the double-support phase, thereby reducing metabolic power requirements. One prototype uses a controlled energy storage and release (CESR) mechanism, while another uses a modulated foot roll-over shape. We have been conducting proof of concept experiments on able-bodied subjects using a foot prosthesis simulator (pictured above). This pneumatic casting boot locks the ankle and allows different foot prostheses to be attached to the bottom for well-controlled data collection. We are just beginning to test amputee subjects with robust prototypes, and have met with a few major prosthesis manufacturing companies. We have some new prototypes that I would like to show you pictures of, but patents are still being filed on these designs, and so exact details cannot yet be revealed here. For more information and preliminary results on the CESR foot, please see the CESR fact sheet: |
This work has been funded by the University of Michigan and a National Science Foundation (NSF) Biomechanics STTR grant.
Last updated: 2/19/2005
References
Brockway, J.M. (1987) Derivation of formulae used to calculate energy expenditure in man. Human Nutrition: Clinical Nutrition 41C: 463-471. | ||
Buckley, J.G., Spence, W.D., Solomonidis, S.E. (1997) Energy cost of walking: comparison of "intelligent prosthesis" with conventional mechanism. Arch. Phys. Med. Rehabil. 78: 330-333. | ||
Colborne, G.R., Naumann, S., Longmuir, P.E., and Berbrayer, D. (1992) Analysis of mechanical and metabolic factors in the gait of congenital below knee amputees. Am. J. Phys. Med. Rehabil. 92: 272 – 278. | ||
Gailey, R.S., Nash, M.S., Atchley, T.A., Zilmer, R.M., Moline-Little, G.R., Morris-Cresswell, N., Siebert, L.I. (1997) The effects of prosthesis mass on metabolic cost of ambulation in non-vascular trans-tibial amputees. Prosthet. Orthot. Intl. 21: 9-16. | ||
Herbert, L. M., Engsberg, J.R., Tedford, K.G., Grimston, S.K. (1994)A comparison of oxygen consumption during walking between children with and without below-knee amputations. Physical Therapy 74: 943. | ||
Lehmann, J.F., Price, R., Boswell-Bessette, S., Dralle, A., Questad, K., deLateur, B.J. (1993) Comprehensive analysis of energy storing prosthetic feet: Flex Foot and Seattle Foot Versus Standard SACH foot. Arch. Phys. Med. Rehabil. 74: 1225-1231. | ||
Lehmann, J.F., Price, R., Boswell-Bessette, S., Dralle, A., Questad, K. (1993) Comprehensive analysis of dynamic elastic response feet: Seattle Ankle/Lite Foot versus SACH foot. Arch. Phys. Med. Rehabil. 74: 853 - 861. | ||
Lemaire, E.D., Nielen, D., and Paquin, M.A. (2000) Gait evaluation of a transfemoral prosthetic simulator. Arch.Phys. Med. Rehabil. 81: 840-843. | ||
McGavock, J.M., Eves, N.D., Mandic, S., Glenn, N.M., Quinney, H.A., Haykowsky, M.J. (2004) The role of exercise in the treatment of cardiovascular disease associated with type 2 diabetes mellitus. Sports Med. 34: 27-48. | ||
Molen, N.H. (1973) Energy/speed relation of below-knee amputees walking on motor-driven treadmill. Int. Z. Angew. Physiol. 31: 173. | ||
Phillips, V.L., (1985) Composite prosthetic foot and leg. U.S. Patent 4,547,913. | ||
Phillips, V.L., (1989) Modular composite prosthetic foot and leg. U.S. Patent 4,822,363. | ||
Poggi, D.L., Burgess, E.M., Moeller, D.E., Hittenberger, D.A., (1987) Prosthetic foot having a cantilever spring keel. U.S. Patent 4,645,509. | ||
Pratt, J. E., Krupp, B. T., Morse, C. J., and Collins, S. H. (2004) The RoboKnee: An Exoskeleton for Enhancing Strength and Endurance During Walking. In Proc. IEEE Int. Conf. Robotics and Automation, New Orleans, LA, 2430-2435. | ||
Robinson, E., Robinson, D., College Park Industries Inc., (1993) Prosthetic foot with ankle joint and toe member. U.S. Patent 5,258,038. | ||
Scherer, R.F., Dowling, J.J., Robinson, M., Frost, G.F., McLean, K. (1999) Mechanical and metabolic work of persons with lower-extremity amputations walking with titanium and stainless steel prostheses: a preliminary study. Journal of Prosthetics and Orthotics 11: 38-42. | ||
Thomas, S.S., Buckon, C.E., Helper, D., Turner, N., Moor, M., Krajbich, J.I. (2000) Comparison of the Seattle Lite Foot and Genesis II Prosthetic Foot during walking and running. Journal of Prosthetics and Orthotics 12:9-14. | ||
Torburn, L., Powers, C.M., Guiterrez, R., Perry, J. (1995) Energy expenditure during ambulation in dysvascular and traumatic below-knee amputees: a comparison of five prosthetic feet. Journal of Rehabilitation Research and Development 32:111-9. |
Last updated: 1/31/2005 miserable failure