MIRA University of Twente
Department of Biomechanical Engineering


Balroom - Effect of velocity on short range stiffness in the ankle joint


Twente University (also open for students from TU Delft)


(Bio-)Mechanical engineering, Electrical engineering, Biomedical engineering or similar




Denise Engelhart (Twente, daily supervisor)

Alfred Schouten



The mechanical behavior of a joint can be described by a (linear) musculoskeletal model of a human limb with intrinsic feedback due to the visco-elasticity of active muscles, and with reflexive feedback (length, velocity and force) of muscle afferents (muscle spindles and Golgi tendon organs).

Description: CrossbridgeMuscles behave as elastic springs during the initial strain phase, indicated as short range stiffness (SRS). Beyond a certain amount of strain the muscle demonstrates a more viscous behavior. The strain at which the muscle transits from elastic- to viscous-like behavior is called the elastic limit and is believed to be the result of breakage of cross-bridges between the contractile filaments.

Assignment introduction

In a recent study of the arm (de Vlugt, 2011) it was shown that the elastic limit, measured in vivo at the wrist joint, is depended on the speed of lengthening. Brief extension rotations were imposed to the wrist joint at four different speeds and at three different levels of voluntary torque. With closed loop system identification techniques (CLSIT), the elastic limit from measured joint angle and torque was quantified. The question now rises if the same behavior exists at the ankle joint. Furthermore, we want to know if CLSIT can be used to investigate the contribution of passive, active and reflexive components in SRS, so more insight can be gained in the underlying (patho-) physiology.


The Bilateral Ankle Perturbator (BAP) consists of two small foot-size platforms driven by an electromotor, which can rotate around the ankle axis; therefore different ankle torques at different speeds can be set and the reaction can be measured over time. The aim is to investigate short range stiffness of the ankle joint using the BAP.


o Literature review on mechanical behavior of a joint including short range stiffness

o Study the effect of angular velocity on SRS using the BAP

o Study the effect of joint torque on SRS using the BAP

o Use system identification techniques to quantitative discriminate between the contribution of passive, active and reflexive components in SRS

o Write a report in the form of a scientific paper

Further information

If you are interested in this assignment, please contact Alfred Schouten (a.c.schouten@tudelft.nl) or Denise Engelhart (d.engelhart@utwente.nl) for further information.