Experimental Research at the REAR Lab
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Everyday Use of Assistive Technology
The REARLab has conducted dozens of projects and studied hundreds of participants in our effort to document and understand the usage of mobility devices in everyday life. Monitoring involves the development and deployment of sensors and instrumentation to unobtrusively document real-world device usage. In some cases, we deploy innovative hybrid research methodologies that combine traditional rehabilitation engineering with social science data collection methods to gain greater context for understanding device use.
Understanding how individuals use their devices is important for a number of reasons. Improving the design of devices requires knowledge about how they are and are not used. Matching an individual with the best assistive technology also benefits from understanding individuals’ real world behavior.
Finally, research studies can be informed by knowledge about device use. For example, we have studied the construct of ‘bouts of mobility’ in an effort to answer “How do people use their wheelchairs.” We found that the median bout speed of full time manual wheelchair users was only 0.44 m/s, much slower than the self-selected speeds often studied in laboratory experiments.
Some examples of technologies we have investigated in the real world include:
· Power tilt-in-space wheelchairs
· Ultra-lightweight manual wheelchairs
· Power adjustable seat height wheelchairs
Relevant REARLab publications about everyday use of assistive technology (see our resources and downloads for a complete listing of publications and more)
- Sonenblum, S.E. and S. Sprigle, Wheelchair use in ultra-lightweight wheelchair users. Disabil Rehabil Assist Technol, 2016: p. 1-6.
- Sonenblum, S.E. and Sprigle, S., Distinct tilting behaviors with power tilt-in-space systems. Disabil Rehabil Assist Technol, 2011. 6: p. 526-535.
- Harris, F., Sprigle, S., Sonenblum, S.E., and Maurer, C.L., The participation and activity measurement system: an example application among people who use wheeled mobility devices. Disability And Rehabilitation. Assistive Technology, 2010. 5(1): p. 48-57.
- Sonenblum, S.E., S.H. Sprigle, J.M. Cathcart, and R.J. Winder, 3D anatomy and deformation of the seated buttocks. J Tissue Viability, 2015. 24(2): p. 51-61.
Tissue Health
Pressure ulcers are a critical problem with negative consequences for the health, activities of daily living, employment, and quality of life of wheelchair users, surgical and ICU patients, and others with limited mobility and sensation. The REAR Lab has a research focus on tissue health, aimed at understanding the pathophysiology of pressure ulcer development, and improving risk assessment in a manner that informs interventions. We aim to reduce the incidence of pressure ulcers by providing quantitative information about biomechanical risk and identifying and developing effective, personalized interventions.
The REARLab’s work on tissue health is broad, but it considers the many factors that impact an individual’s tissue health including intrinsic characteristics about the individual and extrinsic factors such as behavior.
When tissue is loaded for too long, or with particularly high pressures, the resulting tissue deformation leads to damage. Some of our work seeks to understand the tissue deformation that occurs in response to loading. For example, we are measuring seated buttocks tissue deformation of wheelchair users in an upright MRI. Our goal is to find differences deformation in people with different levels of pressure ulcer risk, and to identify clinically measurable, biomechanical risk factors that contribute to seated tissue deformation. In other words, we want to develop a simple clinical tool that allows clinicians to classify their clients’ Biomechanical Risk. Paired with our test method development efforts, the tool would then propose a list of prevention strategies and products that match the risk level.
Clinical practice guidelines dictate that regular pressure reliefs or turning is necessary for the prevention of pressure ulcers. But evidence supporting this guideline is lacking, in large part because most studies have relied on self-report. Our ongoing work includes measuring actual pressure relief and weight shift behavior and relating it to pressure ulcer outcomes. These results will inform individual recommendations for in-seat activity goals. We have also conducted laboratory experiments to relate the real world behavior to the associated physiological responses. We have measured the blood flow and pressure responses to weight shifts, both via leans and power tilt-in-space, and identified which movements provided the greatest biomechanical benefits.
Relevant REARLab publications about tissue health (see our resources and downloads for a complete listing of publications and more)
- Sonenblum, S.E., T.E. Vonk, T.W. Janssen, and S.H. Sprigle, Effects of wheelchair cushions and pressure relief maneuvers on ischial interface pressure and blood flow in people with spinal cord injury. Arch Phys Med Rehabil, 2014. 95(7): p. 1350-7.
- Sprigle, S., S. Sonenblum, and T. Conner-Kerr, mobilityRERC state of the science conference: individualizing pressure ulcer risk and prevention strategies. Disabil Rehabil Assist Technol, 2013. 8(6): p. 454-
- Sonenblum, S.E. and Sprigle, S.H., The impact of tilting on blood flow and localized tissue loading. J Tissue Viability, 2011. 20(1): p. 3-13.
Applied Biomechanics Research
The REARLab also conducts a variety of applied biomechanical research. Examples of two recent studies are presented below.
Plantar Skin Stiffness
Diabetes affects 25.8 million Americans. Complications related to this growing disease impact public health. One secondary complication of diabetes is changes in skin that can contribute to an increased risk for ulceration. Skin of people with diabetes has not been characterized over time nor has the skin’s acute response to exercise been assessed. The objective of this project was to establish the changes in skin properties over time, within different ambient environments, and after acute exercise. This objective sought to address the central hypothesis that skin will demonstrate decreased stiffness and increased elasticity as a result of acute physical activity.
Wendland, D. (2013) The Acute effects of physical activity on the stiffness of the plantar skin of people with and without diabetes. Thesis, Georgia Institute of Technology, Atlanta, GA.
Wheelchair Propulsion Effort
For wheelchair users, the ease of maneuvering a wheelchair is crucial for their mobility and participation in their communities, thus improving their quality of life. From a mechanical design standpoint, the major factors influencing propulsion efforts are inertia and frictional energy loss. On a wheelchair with greater inertia and/or greater frictional loss, a user needs to exert greater instantaneous forces and metabolic costs while completing a maneuver. Greater propulsion effort can lead to difficulty in achieving the desired speed and a higher probability of fatigue over long bouts of mobility. The objective of the study was to define the relative influence of mechanical wheelchair parameters as well as individual physical and biomechanical variables on propulsion efforts during over-ground maneuvers.
Relevant REARLab publications about applied biomechanics research (see our resources and downloads for a complete listing of publications and more)
- Lin, J. (2016) The influence of wheelchair mechanical parameters and human physical fitness on propulsion effort. Thesis, Georgia Institute of Technology, Atlanta, GA.
