# Distributed Sensor Systems

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projects:muscletension

# Measurement of Muscle Tension

Çaǧlar Çetin, Yorick van der Kroef, Marnix Teunissen, Lars Verheijen, Bas Lengkeek, Toma Garofil, Sergi Bidlot
Coach: Duncan van Meeteren
Client: Geert Langereis
August 2016 - November 2016

Ismail Pasazade, Luc Wagener, Yorick van der Kroef, Tom Wullems
Client: Geert Langereis
November 2016 - February 2017

Bart Scholten, Thomas van der Putten, Martijn van de Wijdeven, Luc Wagener, Ruben Hoogenraad, Phine van Hattum, Teun Jacobs
Coach: Bert Huis in 't Veld
Client: Geert Langereis
February 2017 - April 2017

With surface electromyography (sEMG) we can measure the electrical activity of the human muscles. Therefore, sEMG has become a many used method in sports and biomechanical studies. The sEMG measurements are sometimes combined with motion measurements: while sEMG measures the inputs of the muscles, a motion analysis measured the effective outputs of the muscles.

We have the strong impression, that measuring the tension on the muscles can be an even better indicator for the muscle output. The tension of any elastic surface can be measured by applying a force and measuring the displacement. This experiment can easily be done by a linear motor like a solenoid.

The research question for this project was: Determine the tension of a human muscle (biceps or gastrocnemius) by applying pressure with an actuator (solenoid or speaker) while measuring the displacement.

The proposed method to measure the tension of a muscle is to apply a force $F$ and to measure the displacement $\Delta x$. In that case, the tension can be determined by the spring constant $k$ which relates the force and the displacement by $F = k \Delta x$. When using a solenoid (or a speaker) as the actuator, the applied voltage and current relate to the displacement and force. That would mean that if we apply a solenoid current and measure the voltage, the $V$-$I$ relation also relates to the spring constant! Experience yields that this can best be done by using an AC signal (vibration). The set-up is sketched in figure 1. This method, which is in fact impedance spectroscopy, is theoretically explained on te page with the electrodynamic actuator.

Fig. 1: The proposed set-up to measure the muscle tension with a solenoid

The student assignment is to make the electronics to apply a current and measure the voltage (or vice versa) in order to determine the elasticity of an object. It was suggested to find a test object first with similar properties as a human muscle for the experiments. Next, a set-up has to be made to measure the tension (elasticity) of a surface similar to a human muscle in contraction and rest by means of a linear motor like a solenoid or speaker.

The quantitative specifications had to be determined by the project team:

• Find the elasticity of a muscle (biceps) in rest and under contraction
• Find an equivalent experimentation system for both the tense and relaxed states (rubber balls?)
• Select a linear motor to excite the surface with an AC signal (mechanical) having “sufficient” force.
• Find the optimum frequency and amplitude to measure the $V$-$I$ (or $F$-$\Delta x$) relation
File Version Date Description
muscle_tension_final_report_q1_2016-2017.pdf 1.0 November 9, 2016 Final report
2016-2017_q2_expo19_eindverslag_final.pdf 1.0 February 1, 2017 Final report
2016-2017_q3_muscle_strength_expo_19.pdf 1.0 April, 2017 Intermediate report (Dutch)