Using a model for the neuromuscular control of human arm movements, the possible roles of different proprioceptive signals are analyzed. The control model is represented by a neural network and includes both feedback and feedforward control modes. After a learning process, the controller regulates a wide range of arm movements. Evaluation of the roles of different afferent signals shows that se...

OBJECTIVE To evaluate if hyperreflexia (exaggerated reflexes) due to disinhibition is associated with dystonia in Complex Regional Pain Syndrome (CRPS). METHODS Stretch reflexes at the wrist were assessed in healthy controls (n=10) and CRPS-patients with dystonia (n=10). Subjects exerted a wrist flexion torque of 5% of maximum voluntary contraction torque (T(MVC)) to a manipulandum which appl...

OBJECTIVE The external knee adduction moment (EAM) is often considered a surrogate measure of the distribution of loads across the tibiofemoral joint during walking. This study was undertaken to quantify the relationship between the EAM and directly measured medial tibiofemoral contact forces (Fmed ) in a sample of subjects across a spectrum of activities. METHODS The EAM for 9 patients who u...

In the last decade new actuator designs have been presented trying to introduce at mechanical level the advantages of compliance. Ranging from serial elastic actuators to different designs of variable stiffness actuators, various prototypes have been proposed and implemented on robots, thus allowing performance of novel and challenging tasks. Nevertheless some of these new devices often are aff...

BACKGROUND AND PURPOSE Proprioceptive neuromuscular facilitation (PNF) stretches are widely used in athletics and rehabilitation. Although it has been shown that they produce better range-of-motion (ROM) increases than the slow or static stretch, the mechanisms responsible remain an enigma. This study was conducted to determine whether the previously proposed neurophysiological mechanisms of re...

BACKGROUND Work-related Upper Extremity Disorders (WRUEDs) are conceived of as a multifactorial syndrome caused by the effects of excessive repetitive motions, sustained static postures, and muscular stiffness. Our aim is to test an etiological model derived from a theory by Van Galen and Van Huygevoort [2000] Biol Psychol 51:151-171. The theory holds that physical, emotional, and psychosocial ...

This study investigated the neuromuscular mechanisms underlying the initial stage of adaptation to novel dynamics. A destabilizing velocity-dependent force field (VF) was introduced for sets of three consecutive trials. Between sets a random number of 4-8 null field trials were interposed, where the VF was inactivated. This prevented subjects from learning the novel dynamics, making it possible...

In the traditional approaches to Clifford algebras, the Clifford product is evaluated by recursive application of the product of a one-vector (span of the generators) on homogeneous i.e. sums of decomposable (Graßmann), multi-vectors and later extended by bilinearity. The Hestenesian ’dot’ product, extending the one-vector scalar product, is even worse having exceptions for scalars and the need...

Although cats that have been spinalized can also be trained to stand and step with full weight support, directionally appropriate long-latency responses to perturbations are impaired, suggesting that these behaviors are mediated by distinct neural mechanisms. However, it remains unclear whether these responses reflect an attenuated postural response using the appropriate muscular coordination p...

A patient affected by thoracic outlet syndrome, with an involvement of the left lower primary trunk due to a rudimentary cervical rib, developed a severe hand dystonia on the same side. The dystonic posture was characterised by a flexion of the wrist with the fingers curled into the palm. Polygraphic recordings performed on the left flexor digitorum superficialis (FDS4) and extensor digitorum s...