[Risk factors for Parkinson's disease: possibilities for prevention and intervention]. / Risicofactoren voor de ziekte van Parkinson.

Considering age to be the primary risk factor for developing Parkinson's disease and the observation that the Dutch population is rapidly aging, the parkinson prevalence is expected to increase over the coming years, as there is still no cure available for the disease. This has been confirmed by epidemiological data, which show a steady increase of the disease prevalence in the Netherlands for the period 2010-2021. Genetic risk factors only partially explain the disease pathogenesis. Environmental factors, such as exposure to pesticides and trichloroethylene are associated with a higher risk for developing Parkinson's disease. Lifestyle factors such as exercise, caffeine intake and the Mediterranean diet are associated with a lower risk for developing the disease and possibly delay the disease progression. Policy makers and healthcare providers should employ stricter regulations for pesticide use and should stimulate a healthy lifestyle to slow down the increasing prevalence.

Quantifying proprioceptive reflexes during position control of the human arm.

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 parameters were derived, being 1) the mechanical admittance and 2) the reflexive impedance. These FRFs were analysed by a neuromusculoskeletal model that implicitly separates the reflexive feedback properties (position, velocity and acceleration feedback gains) from intrinsic muscle visco-elasticity. The results show substantial changes in estimated reflex gains under conditions of variable bandwidth of the applied force disturbance or variable degrees of external damping. Position and velocity feedback gains were relatively larger when the force disturbance contained only low frequencies. With increasing damping of the environment, acceleration feedback gain decreased, velocity feedback gain remained almost constant and position feedback gain increased. It is concluded that under the aforementioned circumstances, the reflex system increases its gains to maximize the mechanical resistance to external force disturbances while preserving sufficient stability.

Design of a torque-controlled manipulator to analyse the admittance of the wrist joint.

This paper describes the design of a torque-controlled manipulator to identify the dynamics of the wrist joint. With torque disturbances, the subject can actively control the joint angle, giving a natural task. The application of a hybrid haptic controller guarantees linearity over a large bandwidth and adjustable virtual dynamics. The haptic controller has a bandwidth of 50 Hz, meaning that the virtual dynamics are realistically felt at up to 50 Hz. To let the subject 'feel' the torque, disturbances as well as possible the apparent, or virtual, dynamics of the device must be small. The minimal apparent inertia of the device is 1.6 g m(2), which is of the same order as for a normal wrist, and the minimal damping and stiffness are negligible. To judge the accuracy of the manipulator, loads of known physical properties were attached and their parameters were quantified. The parameters of the loads were estimated with a maximum error of 5%. As the eigenfrequency of a (co)-contracted human wrist is approximately 15 Hz, the 50-Hz bandwidth of the haptic device is sufficient to measure all relevant dynamics of the human wrist. With this device, the dynamics of the human wrist joint can be measured under varying virtual dynamics, as well as the effect of neurological dysfunction on human motor control, for example.