Dudley S. Childress

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The non-disabled human ankle joint was examined during walking in an attempt to determine overall system characteristics for use in the design of ankle prostheses. The hypothesis of the study was that the quasi-stiffness of the ankle changes when walking at different walking speeds. The hypothesis was examined using sagittal plane ankle moment versus ankle(More)
OBJECTIVE To examine the hypothesis that roll-over shapes of non-disabled lower limb systems do not change appreciably with walking speed. DESIGN Repeated measures (n = 24). BACKGROUND Roll-over shapes of three lower limb systems are presented. They are: roll-over shapes of the (1) foot, (2) ankle-foot, and (3) knee-ankle-foot systems. Roll-over shapes(More)
To achieve significant improvement in the function of electric-powered, upper-limb prostheses, we believe it is necessary to develop better control interfaces with inherent sensory feedback. Small cineplasties, or other surgical procedures that also externalize the force and excursion of a muscle, could potentially provide this superior control. Connecting(More)
PURPOSE The purpose of this article is to provide an overview of our previous work on roll-over shapes, which are the effective rocker shapes that the lower limb systems conform to during walking. METHOD This article is a summary of several recently published articles from the Northwestern University Prosthetics Research Laboratory and Rehabilitation(More)
The quasi-static response of bulk muscular tissue to indentation was measured on the posterior lower legs of living human subjects. No residual limbs were tested; all subjects had intact lower limbs. For loads up to 7.0 N on an 8.0 mm diameter flat-tipped indentor, the response was repeatable without prior 'preconditioning'. The data at any test location(More)
Roll-over shape is introduced as a significant characteristic of prosthetic feet. The roll-over shapes of the Flexwalk, Quantum, SACH, and SAFE prosthetic feet were determined using three methods; two involving quasi-static loading and one dynamic loading. The results show that foot roll-over shape properties obtained by quasi-static and by dynamic methods(More)
Roll-over characteristics of able-bodied human subjects walking on ramped surfaces were examined in this study. Ten subjects walked at their normal self-selected speed on a level surface, a 5-deg ramp, and a 10-deg ramped surface. Ramps were designed such that ground reaction forces and center of pressure of the ground reaction forces could be measured on(More)
A series of experiments was performed to measure the relationships between the integrated surface EMG and the mechanical state of the cineplastic biceps muscle of one subject. The muscle was studied during static and dynamic isometric contractions at different muscle lengths and during constant velocity isotonic contractions at different loads. The(More)
The control of artificial limbs and other restorative systems is discussed in terms of closed-loop control and sensory feedback. Feedback modalities are classified in three categories: (1) Supplemental Sensory Feedback (2) Artificial Reflexes (3) Control Interface Feedback. Supplemental Sensory Feedback Artificial Reflexes Control Interface Feedback.(More)
Differences in pelvic obliquity between small groups of persons with unilateral lower limb amputation and subjects without amputation were analyzed. Kinematic walking data were collected as six males with transtibial amputation and three males with transfemoral amputation walked over a range of speeds. The pelvic obliquity patterns and amplitudes from the(More)