Foot-worn electronic devices for fitness and sport studies

Aim: This paper gives an overview of foot-worn electronic devices (FWED) for fitness and sport studies, and, in particular, it describes two FWEDs developed at DIII (University of Pavia). Methods: Searching in Google Scholar with keywords ‘‘wearable electronic sport’’ yields a number of results which increased significantly in the last 5 years. Focusing on FWEDs, a relevant number of examples can be found, whether conceived for research purposes, or designed for sportsmen that like to monitor their performances. Film pressure sensors connected to simple data acquisition hardware have been proposed to study plantar pressure in order to improve sports achievements. Inertial sensors are widely exploited in commercial systems: miCoach (Adidas), Nike + (- Nike), Foot Pod (Garmin) and MTwTM (Xsense) cover a wide range of applications based on signals recorded on the shoe. At the Microcomputers and Biomedical Devices Lab. of DIII two FWEDs have been developed: the Wireless Sensors System for Sport Studies (WS) and the Sensorized Insole (SI). The WS is composed by a 2-axes accelerometer, a Bluetooth module and a microcontroller powered by 3 AAA batteries. Small (85 9 60 9 20 mm) and light (200 g), it is fastened to the subject’s ankle by a strap band and provides external connections for 2 force sensors inserted in the shoe. The SI is a technological improvement of WS. Developed in collaboration with Lotto Sport Italia (Italy), it is a 3.7 mm thick insole integrating humidity and temperature sensors, a 3-axes accelerometer, 4 pressure sensors, a microcontroller, a ZigBee module and a LI-ion polymer battery. The weight of a size 43 SI is 47 g. Results: WS was used in a research funded by the league ruling amateur soccer in Italy where we gathered ankles’ vibrations during standardized tasks performed by a soccer team on natural and artificial pitches. Results showed how the fillings used in the artificial pitches modify the interaction between the athlete and the playing surface. WS was also used to test a series of athletic track prototypes (Mondo, Italy). One type of track allowed the athletes to decrease the foot–ground contact time and was selected as the official track of the Beijing 2008 Olympic Games. SI recently passed its testing phase and will be used for a series of experiments, planned at CRIAMS, with the aim of evaluating the comfort level of sport footwear. Conclusion: FWEDs are widely used by research centres and by final users for sport studies. Two FWEDs made by the authors are presented: WS was used for studying the athlete—sport surface interaction, highlighting the effects of materials and structure of the track/turf on foot biomechanics. SI is a promising device for ergonomic studies on sport footwear.