On Modeling Center of Foot Pressure Distortion Through a Medium

Abstract

The center of foot pressure (COP) is a commonly used output measure of the postural control system as it is indicative of the systems stability. A dense piece of foam, i.e., a sponge, can be used to emulate random environmental conditions that distort the ground reaction forces received and interpreted by the cutaneous sensors in the feet; thus introducing uncertainty into the control system. In this paper, the density and size of the sponge was selected such that a subject's weight did not cause full compression. In general, the COP is measured from the bottom of the sponge. As the sponge is used to distort ground reaction forces, it is reasonable then to assume that the COP signal would also be distorted. The use of other sensory information to identify state of balance, and compute necessary balance adjustments, is therefore required. In addition to a sponge, many different types of specialized footwear and inserts are used for people with peripheral neuropathy, such as diabetics. However, it is difficult to design diabetic footwear without a better understanding of the mechanical and physiological effects that different surfaces typical of outdoor terrains, such as a sponge, which cannot be predicted without the sense of the foot, have on balance. Therefore, the goal of this study was to investigate the change of the COP signal from the top and bottom of the sponge. Portable force sensing mats from Vista Medical were used to obtain the COP from the top and bottom of the sponge. The COP measured on the bottom of the sponge is not the same as the COP measured on the top, particularly in the medial-lateral direction. Several linear and nonlinear models were used to identify the unknown plant; i.e., the sponge. Overall, the nonlinear neural network method had superior performance when compared with the linear models. Thus, the results indicate that the signals from the top and bottom of the sponge are in fact different, and furthermore, they are nonlinearly related. A nonlinear mathematical model is proposed which describes COP distortion through a medium such as a sponge. Although the values for the model parameters determined were for a particular sponge, this study suggests that a neural network plant identification model may be applied to any medium other than the sponge; the information can then be used to determine how the balance control model is affected given the sensory information received.

Game-based Exercises for Dynamic Short-Sitting Balance Rehabilitation of People With Chronic Spinal Cord and Traumatic Brain Injuries

“…Flexible pressure mats permit accurate COP recording while eliminating the nonlinear distortions and damping effects produced in the COP trajectory by different materials. 33 A main observation in this case report was that the interactive gaming intervention can motivate people with chronic spinal cord and traumatic brain injuries to practice dynamic movement tasks. This approach was applied effectively to people with severe balance and mobility limitations and to an individual who actively participated in sports.…”

Potentialities and Criticalities of Plantar Pressure Measurements in the Study of Foot Biomechanics: Devices, Methodologies and Applications

“…Novel computational approaches have been tried, validated and used in recent publications dealing with neural networks (Betker AL et al, 2005), fuzzy logics (Senanayake CM, Senanayake SM, 2010 a), cluster analysis (Giacomozzi C., Martelli F, 2006), finite element models (Shiang TY, 1997;Petre M et al, 2008;Gu YD et al, 2010;Chen WM et al, 2010), image processing techniques (Pataky TC et al, 2009;Oliveira FP, Tavares JM, 2010) and so on. Usually, the inputs of such models are represented by the above traditional parameters, their reliability strongly relying on the quality and reliability of raw data.…”

Characterization of the protective capacity of flooring systems using force-deflection profiling

“…Control of balance is dependent on the central nervous system continually integrating visual, vestibular, and somatic sensory information about the surrounding environment, orientation of body parts, and forces acting on the body [20]. Soft foam surfaces detrimentally affect somatic sensory inputs from proprioceptive muscle spindles and cutaneous receptors in the foot and ankle, leading to a delayed or misguided balance control response [21,22].…”