MEASUREMENT AND EXTRACTION OF BASE-OF-SUPPORT GAIT PARAMETER USING A NOVEL ACCURATE HUMAN LOCOMOTIONTRACKING SYSTEM VIA UWB RADIOS M. Abou El-Nasr and Heba Shaban Arab Academy for Science, Technology & Maritime Transport (AASTMT), P.O.Box 1029, Alexandria, Egypt. R.M. Buehrer Wireless @ Virginia Tech, Virginia Polytechnic Institute and State University, P.O.Box VA 24061, Blacksburg, USA. ABSTRACT In this paper, we use our recently proposed highly accurate gait analysis system presented in [1] to measure the base-of-support (BOS) gait parameter, which is defined as the distance from heel- to-heel while walking. This particular gait parameter is known to be of clinical importance, and its measurement accuracy reported in the literature using current highly accurate optical tracking sys- tems is not sufficiently accurate to be clinically accepted. We fur- ther develop a simulation environment using MATLAB to extract gait parameters from the raw-marker-data measured using sophis- ticated optical tracking systems, which commonly require dedi- cated and highly sophisticated software programs. Then, we com- pare the accuracy of the measured BOS using our proposed sys- tem to the extracted BOS from optical tracking systems. We show that our proposed system outperforms the corresponding highly accurate optical tracking systems. In particular, we show that our system provides an accuracy of 1.2% for the BOS measurement compared to 14.6% accuracy for current optical tracking systems. 1. INTRODUCTION Gait analysis is the systematic study of human walking. Observa- tional gait analysis, the standard method of evaluating gait, refers to the visual assessment of a patient’s gait. Gait analysis by ob- server assessment does not use any specialized equipment, and is simply used to observe abnormalities in gait. Clinical gait anal- ysis, also termed as quantitative gait analysis, provides a detailed clinical introduction to understanding and treating walking disor- ders [2], [3]. The identification of gait disorders is commonly as- sessed by the measurement of the spatial and temporal parameters of gait 1 . However, it is worth noting that the techniques and tech- nologies that work well for measuring normal gait often fail when applied to abnormal gait [4], [5]. Standard quantitative gait analysis is based on either optical, magnetic, or ultrasonic motion tracking systems. Sophisticated measurement systems employ optical tracking techniques to track the displacement of markers 2 placed at particular anatomical sites 1 Spatiotemporal parameters of human gait include the step-length, stride-length, velocity, etc. 2 Markers are arranged based on well-defined marker-sets. Markers should be placed at specific anatomical positions, where the objective of data collection is to capture the movement of the underlying skeleton. on limb segments [4], [5], [6]. These systems allow for the as- sessment of a complete three-dimensional kinematic analysis of human movement [5], [7]. For the base-of-support (BOS), the re- ported measurement accuracy is not sufficiently good to be clini- cally accepted. In this paper, we use our recently proposed ambulatory gait analysis system [1] to measure the BOS gait parameter. Further- more, we develop a simulation environment using MATLAB [8] to extract the gait parameters measured using optical tracking sys- tems, which commonly require dedicated software programs placed on servers associated with these measurement systems. We further compare the accuracy of the measured BOS using our proposed system to optical tracking systems. The organization of this paper is as follows. Section 2 gives an overview of the BOS gait parameter measurement accuracy, pro- vides common values for normal gait, and gives a brief overview of our recently proposed gait analysis system. Then, Section 3 intro- duces the BOS measurement procedure, and provides results using our proposed system. Section 4 summarizes the proposed extrac- tion procedure of optical system gait parameters using MATLAB. Finally, conclusions are provided in Section 5. 2. OVERVIEW OF BOS MEASUREMENT AND PROPOSED SYSTEM In this section, we give an overview of common BOS values re- ported in the literature for normal gait. Then, we give a brief overview of our recently proposed ambulatory gait analysis sys- tem. 2.1. Common BOS Values for Normal Gait The BOS is defined as the distance from heel-to-heel while walk- ing; as shown in Figure 1 [9]. It is known to have clinical impor- tance. The BOS is typically equal to 8.5 cm for normal adults with a reported error of 1.17 cm with a relative error ≈ 14.6 % [2], [10]. Thus, the accuracy and reliability of the BOS measurement need to be addressed, as it is one of the important parameters to clinicians. A summary of BOS values in addition to other spatiotemporal gait parameters are provided in Table 1 for normal gait. 2.2. Brief Overview of Proposed System Recently, we proposed a wearable human locomotion tracking and gait analysis system using ultra wideband (UWB) radios [1], [11]. In this paper, we use our system to measure and extract the BOS 188 188 978-1-4244-7000-6/11/$26.00 ©2011 IEEE