Shoe-Embedded Pressure Sensors

This article was updated on the 4th October 2019.

Sander van der Werf / Shutterstock

Runners at the Tokyo 2010 Olympics will be under a great deal of pressure to be the first to the finish line. There is increasing pressure on monitoring an athlete’s performance at the most prestigious sporting event in the world, as well as in elite athlete training.

At London’s 2012 Olympic event, advanced electronic starting blocks were first introduced to track the force of the runner’s heel to give a better representation of how quickly the runner has left the starting block.

There are a number of sensors currently being used to create smart technology in shoes to help monitor the performance of an athlete. Pressure sensors and accelerometers are commonly used to advance sports-performance technology.

Pressure Sensors

Ground reaction force is measured using a pressure sensor to provide data on the speed of a person’s gait. The ground reaction force is the force applied as a result of contact of the body with a surface. In this instance, the pressure sensor works to measure changes in the loading to predict speed. The pressure impacting the point where two surfaces interact (i.e. between the shoe and the foot) is known as the plantar pressure.

In a study by A.J.Y. Lee and colleagues, insole pressure sensors were used to investigate the relationship between peak treadmill acceleration, peak plantar pressure and peak ground reaction force during a running exercise. A dual-axis accelerometer with a data acquisition system attached to a treadmill running board was used in the study. The board gathered information on the peak treadmill acceleration during a running exercise.

Fig. 1 illustrates a standard accelerometer used to measure peak treadmill acceleration.

During a running exercise, the accelerometer was activated by an electronic pulse. In this study, the accelerometer only measured speed in a vertical direction. The study revealed a linear correlation between peak treadmill acceleration and the speed of running.

Three-axis accelerometers with a wireless interface are commonly used in research to measure shoe-integrated sensing. For example, a team lead by Kazumasa Oshima at Kyushu University, Japan implemented such a system to the heel portion of a shoe with two sensors. One sensor was embedded at the toe end of a shoe and the other sensor at the heel.

Field experiments that involved monitoring participants’ gait patterns revealed fluctuation patterns in y-axis acceleration relating to up-down movement of the foot indicating that shoe-embedded sensors are useful for monitoring gait pattern.

Measurement of gait pattern is particularly useful in rehabilitation programs. It is challenging to measure gait patterns for patients when considering the space required to carry out such measurements. Yukinobu Sugimura and colleagues have developed a shoe-embedded sensor device specifically for measuring gait pattern for rehabilitation (Fig. 2).

This study involved use of a shoe-embedded sensor network (consisting of pressure sensors and an accelerometer to detect information on the length and width of a step and the plantar pressure) with a wireless module to transfer the data from the sensor network to a display. The accelerometers used to measure the three axes were positioned inside the shoe with two transmitters placed on the surface of the heel, inside the shoe.

Pressure sensors were also used to measure the change in plantar pressure during an individual’s gait. The display screen was used to present a gait pattern for interpretation by the physician.

Use of a pressure sensor to monitor gait patterns is a highly useful tool for applications such as rehabilitation. Development in this field of research has seen shoe manufacturing companies design shoes with the shoe-embedded sensor in the sole. The shoe-embedded sensor technology is also attractive to the sports industry as it helps athletes keep track of their speed and performance, and coaches effectively train elite athletes to the highest levels.

References

• Lee, A J Y., Chou J., Liu Y., et al. Correlation between treadmill acceleration, plantar pressure, and ground reaction force during running. (P52). Published in:  Estivalet, M., Brisson, P. (2008). The Engineering of Sport 7. Volume 1. France, Paris: Springer Science and Business Media.
• OSHIMA, k., Ishida, Y., Konomi, S., Thepvilojanapong, N., Tobe, Y. A Shoes-Integrated Sensing System for Context-Aware Human Probes. Published in DASFAA’10 Proceedings of the 15th International Conference on CDatabase Systems for Advanced Applications. Volume Part 2. Germany, Berlin: Springer Science and Business Media.
• Sugimura, Y., Wada, F., Makino, K., et al. Development of a shoe-type device for collecting gait information. Published in: Dossel, O., Schlegel, W.C. (2009). Ifmbe Proceedings. Volume 25/9. World Congress on Medical Physics and Biomedical Engineering. 7–12 September 2009. Munich, Germany. Germany, Berlin: Springer Science and Business Media.
• Duffy, V.G. Digital Human Modeling: Third International Conference, ICDHM 2011. Germany, Berlin: Springer Science and Business Media.