Textile pressure sensors for sports applications

Wearable sports trainers are built upon sensor systems recognizing the activities performed by its users. In snowboarding, one of the fastest growing sports in the world, traditional activity recognition approaches make use of pressure insoles with force-sensitive resistors, which, however, are particularly uncomfortable to wear. To make these measurements more convenient, we have developed textile pressure sensors using the principle of a variable capacitor. Electrodes of conductive textiles coated with silver arranged on both sides of compressible spacers made from Croslite™ form a capacitor, whose capacitance indicates the applied pressure. We integrated three sensors into a snowboarding sock at relevant positions under the heel and the ball of the foot. Outdoor experiments on a ski slope in the Matterhorn Glacier Paradise (Zermatt, Switzerland) show that the machine learning algorithm NCC can detect turns, the basic activity of snowboarding, from the sensor data with an accuracy of 84 percent. Moreover, indoor experiments reveal that NCC can clearly distinguish whether a person wearing our sensor socks is standing on the ball of the foot, flat or on the heel. These results suggest the socks might also be used for gait analysis or the monitoring of the in-shoe pressure distribution of runners.