The mechanical properties of the human heel pad: a paradox resolved
| Autor: | R. McNeill Alexander, Peter Aerts, Dominique De Clercq, D.W. Ilsley, R. F. Ker |
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| Rok vydání: | 1995 |
| Předmět: |
Adult
Heel Biomedical Engineering Biophysics Pilot Projects In Vitro Techniques Body weight Weight-Bearing Materials Testing medicine Humans Orthopedics and Sports Medicine Mathematics Aged Leg business.industry Test procedures Rehabilitation Body Weight Pendulum Stiffness Signal Processing Computer-Assisted Structural engineering Middle Aged Elasticity Biomechanical Phenomena medicine.anatomical_structure Energy Transfer Resilience (materials science) Stress Mechanical medicine.symptom business Locomotion |
| Zdroj: | Journal of biomechanics |
| ISSN: | 0021-9290 |
| Popis: | In vivo and in vitro mechanical testing of the human heel pad gave apparently different properties for this structure: the in vivo stiffness is about six times lower, whereas the percentage of energy dissipation is about three times higher (up to 95% loss). It was postulated that this divergence must be ascribed to the lower leg being involved in in vivo heel pad testing. This hypothesis is presently evaluated by applying the two experimental procedures formerly used in the in vivo (an instrumented pendulum) and in vitro (an Instron servo-hydraulic testing machine) investigations on the same isolated heel pad samples. Instron load-deformation cycles mimicking pendulum impacts (i.e. 'first loop-half cycles') are first evaluated and then compared to real pendulum impacts. When performed properly, the pendulum test procedure reveals the same mechanics for isolated heel pads as the Instron does. The load-deformation loops are basically identical. Thus similar non-linear stiffnesses (about 900 kN m-1 at body weight) and comparable amounts of energy dissipation (46.5-65.5%) are found with both types of test, still being largely different from the former in vivo results (150 kN m-1 and 95%, respectively). Therefore, the present findings support the hypothesis that the presence of the entire lower leg in in vivo tests indeed influences the outcome of the measurements. It must be concluded that the previously published in vivo data, if interpreted for the heel pad alone, implied not only an incorrectly low resilience but also a value far too low for stiffness. |
| Databáze: | OpenAIRE |
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