Design and Accuracy of an Instrumented Insole Using Pressure Sensors for Step Count

Abstract

Despite the accessibility of several step count measurement systems, count accuracy in real environments remains a major challenge. Microelectromechanical systems and pressure sensors seem to present a potential solution for step count accuracy. The purpose of this study was to equip an insole with pressure sensors and to test a novel and potentially more accurate method of detecting steps. Methods: Five force-sensitive resistors (FSR) were integrated under the heel, the first, third, and fifth metatarsal heads and the great toe. This system was tested with twelve healthy participants at self-selected and maximal walking speeds in indoor and outdoor settings. Step counts were computed based on previously reported calculation methods, individual and averaged FSR-signals, and a new method: cumulative sum of all FSR-signals. These data were compared to a direct visual step count for accuracy analysis. Results: This system accurately detected steps with success rates ranging from 95.5 ± 3.5% to 98.5 ± 2.1% (indoor) and from 96.5 ± 3.9% to 98.0 ± 2.3% (outdoor) for self-selected walking speeds and from 98.1 ± 2.7% to 99.0 ± 0.7% (indoor) and 97.0 ± 6.2% to 99.4 ± 0.7% (outdoor) for maximal walking speeds. Cumulative sum of pressure signals during the stance phase showed high step detection accuracy (99.5 ± 0.7%–99.6 ± 0.4%) and appeared to be a valid method of step counting. Conclusions: The accuracy of step counts varied according to the calculation methods, with cumulative sum-based method being highly accurate.

Use of Wearable Sensor Technology in Gait, Balance, and Range of Motion Analysis

“…They are typically used in gait analysis to count steps and extract time and distance based parameters. In balance analysis, they are typically used to measure center of pressure to evaluate postural stability [19,26,42,43,71].…”

“…For static balance assessment the most common locations are lumbar, waist, and/or holding the device in the chest/sternum due to the capability of measuring trunk sway at these locations ( Table 3). The most reliable step count comes from insole pressure sensor since it can detect the pressure applied to the sensor once a subject is performing a step [26,42,43,71]. Studies that use IMUs for gait analysis tend to mount the devices on locations below the knee joint, such as feet, ankles and shanks, due to the high movements involved in those areas when a person is walking (Table 3).…”

Special Issue “Body Sensors Networks for E-Health Applications”

“…The system described in Reference [ 3 ] proposes a sensor technology based on sensors integrated in insoles to be placed on shoes for the development of a pedometer adapted for use in elderly people. Pedometers are commonly used for the evaluation of energy expenditure and physical activity in rehabilitation activities, patient monitoring and training.…”

“…However, the precision of these systems, normally based on accelerometers, has been limited in studies conducted in elderly people or patients with pathologies related to brain damage. To address this problem, the authors of Reference [ 3 ] propose an insole with five force-sensitive resistances to measure the foot pressure. Based on the information provided by the sensors, a new method to accounting for the number of steps is proposed.…”

Foot Plantar Pressure Measurement System Using Highly Sensitive Crack-Based Sensor

“…The specific dimensions of he telastomer part are provided in Figure S3. To make the insole pressure sensor, we placed the pressure sensor and injected additional elastomer under the heel and the 1st, 3rd and 5th metatarsals, and the great toe, because the different locations of the sensor may help differentiate the various aspects of the gait cycle [42][43][44].…”