Evaluation of torso stability using the basin of stability chair

WCU Author/Contributor (non-WCU co-authors, if there are any, appear on document)
Walter Dalton Fox (Creator)
Western Carolina University (WCU )
Web Site: http://library.wcu.edu/
Martin Tanaka

Abstract: Low back pain (LBP) is a costly problem in modern health care that affects up to 80% of the population at some point in life. The link between low back and torso instability or spinal motion has not been clearly defined. Past studies evaluating torso dynamics have employed the use of unstable seating apparatuses to analyze various aspects of human torso stability. Traditionally, these devices measure Kinematic Variability (KV). However, previous devices had design limitations making them unable to measure dynamic stability parameters such as the Basin of Stability (BoS). In this research project an innovative new device for measuring unstable seating was designed, constructed, and performance tested. The new device, the BoS Chair, presented several key challenges and required the custom fabrication of each major component utilizing CAD software and CNC machinery. A new seating arrangement was devised using a kneeling chair configuration to isolate the upper torso. The new seating configuration implemented a high deflection angle joint allowing the chair to tilt farther than previous devices enabling the calculation of the basin of stability. The design also required the ability to adjust restorative torque, known simply as the difficulty level. These features required safety measures and a sturdy safety frame to accompany the device. Testing of the new BoS chair required the formulation of Threshold of Stability (ToS) and Basin of Stability test procedures. The ToS procedure tested participants through a series of increasing difficulties until failure was detected. The point of failure marked the threshold of the participant. Using the ToS information, a preliminary BoS procedure was conducted to record temporal movement parameters using a gyroscopic sensor. Tests were conducted with six male and six female participants. ToS trials were statistically compared and analyzed, revealing that height and weight had a significant confounding effect on the results. The effect was successfully remedied through normalization. It showed that the BoS chair could be used to study the torso balance control of participants regardless of their size. The stability graphs and stabilograms generated from the preliminary BoS data indicated that the recording device and trial methods were sufficient. These initial Basin of Stability tests will form the foundation for the development of future BoS testing protocols. The BoS chair is as a durable and flexible tool for measuring torso stability that was designed to detect Lagrangian Coherent structures in a novel way. The preliminary BoS data collected in this research will be useful for future Basin of Stability research and provide preliminary data for grant proposals. With the device constructed and baseline data available for human subjects (i.e. controls), we are now prepared for future projects that measure torso stability in patient populations to improve our understanding of this condition and its effect on low back pain.

Additional Information

Language: English
Date: 2013
basin of stability, low back pain, torso stability
Back -- Mechanical properties -- Research -- Technological innovations
Human mechanics -- Research -- Technological innovations
Human engineering -- Research -- Technological innovations

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