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A rigorous model of reflex function indicates that position and force feedback are flexibly tuned to position and force tasks

Mugge, W. (author), Abbink, D.A. (author), Schouten, A.C. (author), Dewald, J.P.A. (author), Van der Helm, F.C.T. (author)

This study aims to quantify the separate contributions of muscle force feedback, muscle spindle activity and co-contraction to the performance of voluntary tasks (‘‘reduce the influence of perturbations on maintained force or position’’). Most human motion control studies either isolate only one contributor, or assume that relevant reflexive...

journal article 2009

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Design and evaluation of two different finger concepts for body-powered prosthetic hand

Smit, G. (author), Plettenburg, D.H. (author), Van der Helm, F.C. (author)

The goal of this study was to find an efficient method of energy transmission for application in an anthropomorphic underactuated body-powered (BP) prosthetic hand. A pulley-cable finger and a hydraulic cylinder finger were designed and tested to compare the pulley-cable transmission principle with the hydraulic cylinder transmission principle....

journal article 2014

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Muscle weakness and lack of reflex gain adaptation predominate during post-stroke posture control of the wrist

Meskers, C.G.M. (author), Schouten, A.C. (author), De Groot, J.H. (author), De Vlugt, E. (author), Van Hilten, B.J.J. (author), Van der Helm, F.C.T. (author), Arendzen, H.J.H. (author)

Background Instead of hyper-reflexia as sole paradigm, post-stroke movement disorders are currently considered the result of a complex interplay between neuronal and muscular properties, modified by level of activity. We used a closed loop system identification technique to quantify individual contributors to wrist joint stiffness during an...

journal article 2009

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Relating reflex gain modulation in posture control to underlying neural network properties using a neuromusculoskeletal model

Schuurmans, J. (author), Van der Helm, F.C.T. (author), Schouten, A.C. (author)

During posture control, reflexive feedback allows humans to efficiently compensate for unpredictable mechanical disturbances. Although reflexes are involuntary, humans can adapt their reflexive settings to the characteristics of the disturbances. Reflex modulation is commonly studied by determining reflex gains: a set of parameters that quantify...

journal article 2010

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Analysis of isometric cervical strength with a nonlinear musculoskeletal model with 48 degrees of freedom

De Bruijn, E. (author), Van der Helm, F.C.T. (author), Happee, R. (author)

Background: Musculoskeletal models served to analyze head–neck motion and injury during automotive impact. Although muscle activation is known to affect the kinematic response, a model with properly validated muscle contributions does not exist to date. The goal of this study was to enhance a musculoskeletal neck model and to validate passive...

journal article 2015

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Development of a comprehensive musculoskeletal model of the shoulder and elbow

Asadi Nikooyan, A. (author), Veeger, H.E.J. (author), Chadwick, E.K.J. (author), Praagman, M. (author), Van der Helm, F.C.T. (author)

The Delft Shoulder and Elbow Model (DSEM), a musculoskeletal model of the shoulder and elbow has been extensively developed since its introduction in 1994. Extensions cover both model structures and anatomical data focusing on the addition of an elbow part and muscle architecture parameters. The model was also extended with a new inverse...

journal article 2011

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Fixed Dystonia in Complex Regional Pain Syndrome: A Descriptive and Computational Modeling Approach

Munts, A.G. (author), Mugge, W. (author), Meurs, T.S. (author), Schouten, A.C. (author), Marinus, J. (author), Lorimer Moseley, G. (author), Van der Helm, F.C.T. (author), Van Hilten, J.J. (author)

Background: Complex regional pain syndrome (CRPS) may occur after trauma, usually to one limb, and is characterized by pain and disturbed blood flow, temperature regulation and motor control. Approximately 25% of cases develop fixed dystonia. Involvement of dysfunctional GABAergic interneurons has been suggested, however the mechanisms that...

journal article 2011

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Quantifying Proprioceptive Reflexes During Position Control of the Human Arm

Schouten, A.C. (author), De Vlugt, E. (author), Van Hilten, J.J. (author), Van der Helm, F.C. (author)

This study aimed to analyse the dynamic properties of the muscle spindle feedback system of shoulder muscles during a posture task. External continuous force disturbances were applied at the hand while subjects had to minimize their hand displacements. The results were analysed using two frequency response functions (FRFs) from which the model...

journal article 2008

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Comprehensive neuromechanical assessment in stroke patients: Reliability and responsiveness of a protocol to measure neural and non-neural wrist properties

Van der Krogt, H. (author), Klomp, A. (author), De Groot, J.H. (author), De Vlugt, E. (author), Van der Helm, F.C.T. (author), Meskers, C.G.M. (author), Arendzen, J.H. (author)

Background: Understanding movement disorder after stroke and providing targeted treatment for post stroke patients requires valid and reliable identification of biomechanical (passive) and neural (active and reflexive) contributors. Aim of this study was to assess test-retest reliability of passive, active and reflexive parameters and to...

journal article 2015

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Comparison of Two Methods for In Vivo Estimation of the Glenohumeral Joint Rotation Center (GH-JRC) of the Patients with Shoulder Hemiarthroplasty

Asadi Nikooyan, A. (author), Van der Helm, F.C.T. (author), Westerhoff, P. (author), Graichen, F. (author), Bergmann, G. (author), Veeger, H.E.J. (author)

Determination of an accurate glenohumeral-joint rotation center (GH-JRC) from marker data is essential for kinematic and dynamic analysis of shoulder motions. Previous studies have focused on the evaluation of the different functional methods for the estimation of the GH-JRC for healthy subjects. The goal of this paper is to compare two widely...

journal article 2011

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Design of Perturbation Signals for the Estimation of Proprioceptive Reflexes

Schouten, A.C. (author), De Vlugt, E. (author), Van der Helm, F.C.T. (author)

This study aimed to identify the functional contribution of reflexes to human motor control during posture maintenance. Continuous random force disturbances were applied at the hand while the subjects were instructed to minimize the deviation resulting from the force disturbances. The results were analyzed in the frequency domain with frequency...

journal article 2008

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EMG feedback tasks reduce reflexive stiffness during force and position perturbations

Forbes, P.A. (author), Happee, R. (author), Van der Helm, F.C.T. (author), Schouten, A.C. (author)

Force and position perturbations are widely applied to identify muscular and reflexive contributions to posture maintenance of the arm. Both task instruction (force vs. position) and the inherently linked perturbation type (i.e., force perturbations-position task and position perturbations-force tasks) affect these contributions and their mutual...

journal article 2011

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A novel self-aligning mechanism to decouple force and torques for a planar exoskeleton joint

Schorsch, J.F. (author), Keemink, A.Q.L. (author), Stienen, A.H.A. (author), Van der Helm, F.C.T. (author), Abbink, D.A. (author)

The design of exoskeletons is a popular and promising area of research both for restoring lost function and rehabilitation, and for augmentation in military and industrial applications. A major practical challenge to the comfort and usability for exoskeletons is the need to avoid misalignment of the exoskeletal joint with the underlying human...

journal article 2014

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Energy efficient walking with central pattern generators: From passive dynamic walking to biologically inspired control

Verdaasdonk, B.W. (author), Koopman, H.F.J.M. (author), Van der Helm, F.C.T. (author)

Like human walking, passive dynamic walking—i.e. walking down a slope with no actuation except gravity—is energy efficient by exploiting the natural dynamics. In the animal world, neural oscillators termed central pattern generators (CPGs) provide the basic rhythm for muscular activity in locomotion. We present a CPG model, which automatically...

journal article 2009

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The intermuscular 3–7 Hz drive is not affected by distal proprioceptive input in myoclonus-dystonia

Van der Meer, J.N. (author), Schouten, A.C. (author), Bour, L.J. (author), De Vlugt, E. (author), Van Rootselaar, A.F. (author), Van der Helm, F.C.T. (author), Tijssen, M.A.J. (author)

In dystonia, both sensory malfunctioning and an abnormal intermuscular low-frequency drive of 3–7 Hz have been found, although cause and eVect are unknown. It is hypothesized that sensory processing is primarily disturbed and induces this drive. Accordingly, experimenter-controlled sensory input should be able to inXuence the frequency of the...

journal article 2010

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Sensory Weighting of Force and Position Feedback in Human Motor Control Tasks

Mugge, W. (author), Schuurmans, J. (author), Schouten, A.C. (author), Van der Helm, F.C.T. (author)

In daily life humans integrate force and position feedback from mechanoreceptors, proprioception, and vision. With handling relatively soft, elastic objects, force and position are related and can be integrated to improve the accuracy of an estimate of either one. Sensory weighting between different sensory systems (e.g., vision and...

journal article 2009

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Identifying intrinsic and reflexive contributions to low-back stabilization

Van Drunen, P. (author), Maaswinkel, E. (author), Van der Helm, F.C.T. (author), Van Dieën, J.H. (author), Happee, R. (author)

Motor control deficits have been suggested as potential cause and/or effect of a-specific chronic low-back pain and its recurrent behavior. Therefore, the goal of this study is to identify motor control in low-back stabilization by simultaneously quantifying the intrinsic and reflexive contributions. Upper body sway was evoked using continuous...

journal article 2013

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Human error in strabismus surgery: Quantification with a sensitivity analysis

Schutte, S. (author), Polling, J.R. (author), Van der Helm, F.C.T. (author), Simonsz, H.J. (author)

Background- Reoperations are frequently necessary in strabismus surgery. The goal of this study was to analyze human-error related factors that introduce variability in the results of strabismus surgery in a systematic fashion. Methods- We identified the primary factors that influence the outcome of strabismus surgery. For each of the human...

journal article 2008

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Integration of Sensory Force Feedback Is Disturbed in CRPS-Related Dystonia

Mugge, W. (author), Van der Helm, F.C.T. (author), Schouten, A.C. (author)

Complex regional pain syndrome (CRPS) is characterized by pain and disturbed blood flow, temperature regulation and motor control. Approximately 25% of cases develop fixed dystonia. The origin of this movement disorder is poorly understood, although recent insights suggest involvement of disturbed force feedback. Assessment of sensorimotor...

journal article 2013

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The relation between neuromechanical parameters and Ashworth score in stroke patients

De Vlugt, E. (author), De Groot, J.H. (author), Schenkeveld, K.E. (author), Arendzen, J.H. (author), Van der Helm, F.C.T. (author), Meskers, C.G.M. (author)

Quantifying increased joint resistance into its contributing factors i.e. stiffness and viscosity ("hypertonia") and stretch reflexes ("hyperreflexia") is important in stroke rehabilitation. Existing clinical tests, such as the Ashworth Score, do not permit discrimination between underlying tissue and reflexive (neural) properties. We propose an...

journal article 2010