Creating a Portable System to Measure the Forces Developed in Ultra-Endurance Races

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"The ease and speed of graphical prototyping in the LabVIEW environment with the potential of calculation and reduced size of the myRIO card make this platform a success."

- Paolo Boscariol, Università di Udine - DIEGM

The Challenge:
Creating a highly portable and lightweight device that can measure and record the contact forces between an athlete’s foot and the ground during runs both at amateur and professional levels. The data acquired provides analysis of the mechanics of running and the expenditure of energy by the athlete.

The Solution:
Using a myRIO device to build a high-performance system that can quickly acquire data from pressure sensors, grouped into three analog channels and a load cell, built into a special sole inserted into the shoe of the athlete for analysis of the forces of horizontal thrust exchanged between the foot and ground.

Paolo Boscariol - Università di Udine - DIEGM
E. Shojaei Barjuei - Università di Udine - DIEGM
A. Gasparetto - Università di Udine
N. Giovanelli - Università di Udine - DSMB
P. Taboga - Università di Udine -DSMB
S. Lazzer - Università di Udine - DSMB

The study of the mechanics of running is a very important application, if the number of professional athletes and amateurs that test themselves in this sport are to be considered. In addition, in recent years, there has been a growing interest for new disciplines, such as mountain climbing and ultra marathons, which subject athletes to very tiring tests. With this in mind, numerous studies have been developed to obtain realistic assessments of the “correct” method of running to evaluate biomechanical elements such as the contact time between the foot and ground, the flight time, the frequency of the stride, and especially the forces exchanged between the foot and ground.

The solutions developed so far are dedicated to acquiring data in the laboratory through the use of sensor-fitted platforms, treadmills, and systems of vision. These devices, though very precise and advanced, do not allow seeing the athlete in more realistic conditions, that is, while running on the track or in open spaces. Other wearable devices have been developed, however, they are applicable for only the analysis of the mechanics of walking and do not allow the athlete to run in a natural way.

The purpose of this study is to develop a device equipped with the following features:

  • High portability
  • High accuracy
  • The ability to acquire the vertical and horizontal forces exchanged between athlete and ground
  • Integration of sensors in a sole of limited thickness

The system we developed is composed of a wearable acquisition system, based on the myRIO architecture, and a sensing insole inserted into the shoe of the athlete. The sole, whose thickness is only 7 mm, contains in its interior a FUTEK load cell that can read the forces exchanged in horizontal direction between the foot and ground. It is also equipped with force-sensing resistors to detect the forces exchanged in the vertical direction between the foot and ground. The voltages obtained from these sensors are grouped into three analog channels. The fourth analog channel is constituted by the tension signal that represents the force detected by the load cell.

The force-sensing resistors behave as functioning variable resistors of the pressure applied to them. The signal is transformed into a tension change by means of a simple resistive divider and an operational amplifier. With this solution, we can obtain a good signal-to-noise ratio, and then carry out reliable readings. The conditioning of the signal from the load cell is carried out by an amplifier for strain gages RS846-171.

The acquisition software and data logging implemented on the edge of the myRIO device allows the athlete, through the use of a key that is already present on the card, to manage the acquisition and launch, pause, resume, or end the cycle of data acquisition. The device’s state of operation is indicated by the various LEDs on the myRIO chassis.

In addition to signals from the sensing insole, the program gives us the ability to record acceleration data on three axes measured on the myRIO device. Given that this is mounted on a belt worn by the athlete, the acceleration datum are significant for the estimation of the acceleration of the center of mass, a very important fact for the biometric analysis of running.

The acquired data is saved on a USB key mounted in the prepared slot on the myRIO card, in a text file compatible with all data analysis programs.

Also under development is a new version of the measurement and acquisition program that can transmit the data that is acquired live by exploiting the potential of a WiFi module mounted on the myRIO card, to be able to realize a telemetry in direct while running.

The first device prototype is currently at an advanced stage in verifying functionality and accuracy—various numerical feedback, carried out in comparison with platforms of force, confirms the accuracy of results and the validity of the approach. The ease and speed of graphical prototyping in the LabVIEW environment with the potential of calculation and reduced size of the myRIO card makes this platform a success; however, the success of the application should also be measured by the fact that we developed the device with a budget considerably lower than that provided for the purchase of devices from the laboratory normally used for diagnostics of the mechanics of walking.

By using myRIO, we quickly developed a low-cost application that gave us the ability to obtain very precious data acquired during the workouts of athletes. The device is in the light complex and does not prevent the normal conduct of sport.

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