Plantar Pressure Sensors Research Articles

Multisensory control of human upright stance

The interaction of different orientation senses contributing to posture control is not well understood. We therefore performed experiments in which we measured the postural responses of normal subjects and vestibular loss patients during perturbation of their stance. Subjects stood on a motion platform with their eyes closed and auditory cues masked. The perturbing stimuli consisted of either platform tilts or external torque produced by force-controlled pull of the subjects' body on a stationary platform. Furthermore, we presented trials in which these two stimuli were applied when the platform was body-sway referenced (i.e., coupled 1:1 to body position, by which ankle joint proprioceptive feedback is essentially removed). We analyzed subjects' postural responses, i.e., the excursions of their center of mass (COM) and center of pressure (COP), using a systems analysis approach. We found gain and phase of the responses to vary as a function of stimulus frequency and in relation to the absence versus presence of vestibular and proprioceptive cues. In addition, gain depended on stimulus amplitude, reflecting a non-linearity in the control. The experimental results were compared to simulation results obtained from an 'inverted pendulum' model of posture control. In the model, sensor fusion mechanisms yield internal estimates of the external stimuli, i.e., of the external torque (pull), the platform tilt and gravity. These estimates are derived from three sensor systems: ankle proprioceptors, vestibular sensors and plantar pressure sensors (somatosensory graviceptors). They are fed as global set point signals into a local control loop of the ankle joints, which is based on proprioceptive negative feedback. This local loop stabilizes the body-on-foot support, while the set point signals upgrade the loop into a body-in-space control. Amplitude non-linearity was implemented in the model in the form of central threshold mechanisms. In model simulations that combined sensor fusion and thresholds, an automatic context-specific sensory re-weighting across stimulus conditions occurred. Model parameters were identified using an optimization procedure. Results suggested that in the sway-referenced condition normal subjects altered their postural strategy by strongly weighting feedback from plantar somatosensory force sensors. Taking this strategy change into account, the model's simulation results well paralleled all experimental results across all conditions tested.

A shear and plantar pressure sensor based on fiber-optic bend loss

Lower-limb complications associated with diabetes include the development of plantar ulcers that can lead to infection and subsequent amputation. While we know from force-plate analyses that medial/lateral and anterior/posterior shear components of ground-reaction forces exist, little is known about the actual distribution of these stresses during daily activities or about the role that shear stresses play in causing plantar ulceration. Furthermore, one critical reason why these data have not been obtained previously is the lack of a validated, widely used, commercially available shear sensor, partly because of the various technical issues associated with measuring shear. In this study, we present a novel means of transducing plantar pressure and shear stress with a fiber-optic sensor. The pressure/shear sensor consists of an array of optical fibers lying in perpendicular rows and columns separated by elastomeric pads. We constructed a map of normal and shear stresses based on observed macrobending through the intensity attenuation from the physical deformation of two adjacent perpendicular fibers. Initial results show that this sensor exhibits low noise and responds to applied normal and shear loads with good repeatability.

足底内蔵センサーを用いた足関節モーメントの推定(J05-2 ライフサポート(2),J05 ライフサポート)

Generally, joint moment of human body is measured by using 3D motion analysis system and force plate. However, such a system is very expensive and size of system is very large. In this paper, we propose a new method for measuring ankle joint moment and reaction force by using wearable plantar pressure sensors. Also to make the calibration method easier, we propose a new simple estimation algorithm. Experimental study is carried out and it can be seen that experimental results of the proposed method compare well with the results of conventional method.

A multisensory posture control model of human upright stance

We present a multisensory postural control model based on experiments where the balance in normal subjects and vestibular loss patients was perturbed by application of external torque produced by force-controlled pull stimuli. The stimuli were applied while subjects stood on a stationary or body-sway-referenced motion platform with eyes closed and auditory cues masked. Excursions of the center of mass (COM) and the center of pressure (COP) were analyzed using a systems analysis approach. The results were compared to an 'inverted pendulum' model of posture control. The model receives input from four sensors: ankle proprioceptors, semicircular canals, otoliths, and plantar pressure sensors (somatosensory graviceptors). Sensor fusion mechanisms are used to yield separate internal representations of foot support motion, gravity, and external torque (pull). These representations are fed as global set point signals into a local control loop based on ankle proprioceptive negative feedback. This set point control upgrades the proprioceptive body-on-foot (support) stabilization into a body-in-space control which compensates for support tilt, gravity, and contact forces. This compensation occurs even when the stimuli are combined or a voluntary lean is superimposed. Model simulations paralleled our experimental findings.

Development of a Closed Kinetic Chain Power Training Device for the Hip Rotators

Introduction: Golfers with optimal transverse plane rotational capability, particularly through the hip joints are better able to generate effective golf swing power. Unfortunately, a device that enables controlled, progressively increased training resistance to the hip rotator muscles in a manner that functionally simulates the golf swing does not presently exist. The purpose of this single subject, crossover design study was to compare hip rotator muscle electromyographic (EMG) amplitudes and activation sequences during a golf swing, and during a simulated golf swing on a pneumatic resistance closed kinetic chain exercise device designed specifically to train the muscular rotators of the hips. Methods: A 52-year-old nonimpaired, right handed male (180 cm, 81.9 kg) who had trained on the device for six months served as the test subject. Following static stretching of the low back and extremities, the subject performed a standard warm-up of 10–12 progressively more intense practice golf swings with a standard driver. Following this bilateral hip external rotator/abductor (gluteus maximus) and hip adductor/internal rotator muscle groups were instrumented with surface EMG electrodes and in-shoe plantar pressure sensors (for event timing purposes). Norquest (Noraxon, Scottsdale, AZ) EMG and Pedar (Novel, Minneapolis, MN) pressure sensor systems triggered from side-by-side laptop computers were used for both data collection and analysis. Each trial consisted of three complete movements for the given condition with alternating order to control for potential order effects. Although the device can also provide eccentric resistance, only minimal (35–40 psi) and moderate (75–80 psi) concentric resistances were evaluated. Results: Both minimal (MIN) and moderate (MOD) device resistances displayed similar muscle activation duration, timing of peak EMG amplitudes, and muscle activation sequencing (relative to peak left foot plantar force onset) compared to the golf swing for the right and left gluteus ▭ maximus (GM) and hip adductor (HA) muscles (Fig. 1). As the device was set with increasing concentric resistance, progressive and predictable increases in right (17%, 37%) and left (9%, 28%) peak GM (Fig. 2) and right (5%, 33%) and left (25%, 30%) HA (Fig. 3) muscle activation amplitudes were observed.Fig. 1Fig. 2Fig. 3Discussion: The pneumatic resistance closed kinetic chain exercise device provided an effective and safe method of progressively increasing concentric resistance to increase hip rotator power during transverse plane movement. By applying resistance in functionally similar movement patterns and velocities, the hip rotators can be trained to facilitate greater crossover to golf performance. Comparative training effect studies on specific golf performance parameters and with other sport movements that require hip rotator muscle power are being planned.

A laser plantar pressure sensor for the diabetic foot

This paper describes the design and development of a high-resolution pressure sensor for use in the field of foot pressure measurement. The device uses an interferometry technique that involves the use of a laser light directed onto a pressure sensitive plate. The pressure plate compresses when a load is applied, and it is this compression which is measured by the interferometry technique. The interference pattern (interferogram) produced represents the pressure distribution across the plate. The interferogram is inputted into the computer using a high pixel CCD camera and video capture card. A fringe analysis program then converts the interferogram into a three-dimensional image of the pressure distribution. A prototype system is described and the initial results show that the system can produce a high resolution image with dynamic capabilities.

In-shoe plantar pressure measurement of the first metatarsophalangeal joint in asymptomatic patients.

Using an in-shoe plantar pressure sensor, the pressure under the first metatarsophalangeal (MTP) joint was measured in 20 asymptomatic control subjects during their normal gait. A 7-micron in-shoe pressure sensor recorded the pressure under the first MTP joint in the 20 volunteers while they were wearing their normal footwear (athletic footwear), a wooden postoperative shoe, a fiberglass short leg walking cast, and a postoperative shoe with a first MTP joint cutout orthotic device. The results showed both casting, and the postoperative shoe with the first MTP joint cutout orthotic device significantly reduced pressure under the first MTP joint compared with normal footwear, with an average decrease of 31% and 43%, respectively. However, the standard postoperative shoe did not significantly reduce first MTP pressure compared with normal footwear. Certain surgeries performed on the distal first metatarsal may benefit from a diminution of loading forces encountered during normal gait. The results of this study indicate that a reduction of first MTP pressures can best be accomplished with either a postoperative shoe with a cutout orthotic device or a short leg walking cast. A standard postoperative shoe showed inconsistent results and had no statistically significant effect on decreasing the pressure under the first MTP joint.