Staff members involved
Karin de Gooijer – van de Groep, MSc
Prof. dr. ir. Herman van der Kooij
Prof. dr. Frans van der Helm
Ir. Leonard van Schelven (UMC Utrecht)
Dr. P.L. Oey, (UMC Utrecht)
Background
Human muscle reflexes can be regarded as closed loop control systems, consisting of muscles (actuators), the central nervous system (controller) and the muscle mechanoreceptors, notably the muscle spindles and Golgi tendon organs. The mechanoreceptors are sensitive to muscle length, velocity and force. To understand this reflex system, mathematical physiological models can be used. The model parameters can be estimated by applying mechanical stimuli to subjects, using robotic manipulators and measuring the applied force, position and EMG. With this method, it has for instance been shown that the loop-gain of the reflex control loop can vary, depending on the task given to the subject (e.g. hold this position, or: maintain a steady force). However, this method can not discriminate between the effects of muscle mechanoreceptors and the central nervous system, since there is no information about the mechanoreceptor output. Microneurography, in which a micro-electrode is inserted in a nerve bundle, can be used to measure mechanoreceptor signals.
Goal
In this project, microneurographic recordings of signals in peripheral nerves will be used for more detailed identification of the dynamics of the neuromuscular system. Dynamic and non-linear properties of the muscle mechanoreceptors will be investigated. Interesting is also the role of the fusimotor system. The fusimotor system can change the mechanical sensitivity of the muscle spindles via efferent nerve signals. This would influence the reflex loop gain.
Methods
Microneurography is infamous for being hard to perform in practice. It is hard to find a useful electrode position within the nerve bundle, and it is hard to hold such a position long enough to gather data. The first step in this project is therefore the investigation of a methodological variant of microneurography which uses an electrode with a bigger contact area. We hypothesize that this will improve the practical feasibility of the measurements in human subjects.
Collaboration
This project is a joint project of the University of Twente, UMC Utrecht and the TU Delft
UNIVERSITY OF TWENTE, ENSCHEDE
Laboratory for biomechanical Engineering, MIRA institute for biomedical engineering and technical medicine
UMC UTRECHT
Ir. Leonard van Schelven is supported by the department of Medical Technology and Clinical Physics.
Dr. P.L. Oey, clinical neurophysiologist, Rudolf Magnus Institute of Neuroscience (advisor)
TU DELFT 
Department of BioMechanical Engineering, Neuro Muscular Control Lab