Research Focus: Split-belt walking involves walking on two side-by-side treadmill belts moving at different speeds. This approach is widely used to study coordination of the legs during locomotor adaptation and has potential for post-stroke rehabilitation. Like stroke patients, amputees have step length asymmetries and limited propulsion from the affected leg, but correcting these asymmetries in amputees using split-belt walking has not been previously attempted. They have shown that both amputees and healthy individuals reduce propulsive work done during single limb stance as they adapt to split-belt walking. The decrease in this inefficient form of propulsion tracks with decreases in metabolic cost during adaptation (Selgrade, Toney and Chang, in preparation).
Also, over the course of adaptation, both amputees and healthy individuals increase negative work during early double support when the foot hits the fast belt, suggesting that little metabolic energy is lost by braking when stepping on the fast belt. He is also studying how trans-tibial amputees adapt to the split-belt condition when it is gradually introduced by slowly accelerating one belt. Gradually introduced perturbations are more suited for clinical use, because they challenge balance less than large, sudden perturbations and result in longer-lasting learning. Below are figures illustrating data collected thus far.
Research Focus: Foot orthoses have many applications for a variety of foot disorders and pathologies. In general, their main goal is to control the movement of the skeletal bones in the feet. The loads transmitted through the foot can be mitigated and changed by the geometry and material properties of the orthosis. Currently, there is no established formula to determine what specific material characteristic is desired in the orthosis over another, which means that the clinician, based on his experience, must make this decision without the aid of scientific data. In addition to this, different physical activities require different stiffness values. Harnessing the technology of granular jamming (commonly seen in robotic grippers) and negative pressure, this variable stiffness quality can be achieved in an orthotic insole.
A robotic gripper is composed of an enclosed nylon membrane filled with a granular media. When negative pressure is applied, the membrane can conform to the shape of the object and pick it up. Other medical devices employ similar technology (such as the Center for International Rehabilitation’s sand casting system for prosthetic sockets or wheelchair-seat shaping systems) that help capture the variable geometries of the human body. This project’s aim is to create a variable stiffness orthosis to allow for a greater range of material properties in one device. This means that the device can be adjusted for the requirements of different tasks (i.e. running or walking). This single device would be able to simulate the material properties of a wide range of orthotic materials, allowing for treatment and physical activity adjustments.
Research Focus: We have used uncontrolled manifold (UCM) analysis (Scholz and Schoner 1999) to investigate how upright standing posture is controlled in terms of coordination of control elemental variables to stabilize important task relevant variables, with the intent to understand the effect of age and other environmental changes on postural control coordination. Results of UCM variance analysis in muscle torque space (ankle, knee, hip and lumbar spine) related to variability of the CoM position for four subjects when standing either on a normal or narrow support surface. The variance components (left ordinate) and the normalized difference (right ordinate) are presented. A normalized difference close to 1.0 indicates that most of the variance is VUCM. Standing on a narrow base increased VUCM and VORT relatively proportionally (bars filled with diagonal fill). A substantial reduction in the relative difference (grey bars compared to block-filled bars) after randomization of the muscle torques occurred on both support surfaces, slightly more so on the narrow support. The results support the hypothesis that active coordination among the joint muscle torques acts to stabilize the CoM position.
Research Focus: We are looking for a way to measure joint torques in rats using a biplanar x-ray system, which is one of 6 in the nation, and a force plate integrated walkway. We are interested in the joints of the hind limb: MTP joint, ankle, knee, and hip. Rat joint torques have not been accurately measured yet using a biplanar x-ray system. Given that rats are a common animal model when looking at most physiological studies, knowing more about the rat is very important. These findings can be used in gait studies or rehabilitation efforts, joint degeneration, being able to quantify decreases in generated torque.
Research Focus: I have been assisting with preliminary testing on the new biplanar x-ray system. Primarily, I have been looking into markerless tracking options to be implemented when taking x-ray videos of rats during gait. We want to avoid marker-based studies as these are more invasive. My broad intersests are in prosthetics and orthotics.
Research Focus: I am interested in robotic prosthetics and neural controls.