About Vrije Universiteit, Amsterdam 

The aim of the research within this theme is to prevent or recover damage to the motor system, due to disposition, ageing, inadequate nutrition, incorrect movement or loading habits. This is found in patients with osteoporosis, arthrosis and discus degeneration, as well as in patients with damaged bone, cartilage or muscle tissues. Tissue regeneration will be possible by means of mechanical loading and through growth factors, hormones and medication. A very important future tool for the regeneration of tissue will be the use of stem cells which are able to differentiate in bone, cartilage and muscle cells. This will be achieved by comparing results from tissue culture and animal models to computer simulations of the motor system and to biomechanical research in clinical trials with patients.

The primary aim of this theme is to increase understanding of the dynamics (disease, injury, recovery, adaptation, and optimization) of the neuro-musculo-skeletal system in the light of its function as a system subserving functional movement. Combinations of biomechanical and (neuro-) physiological tools are used to study the dynamics in experimental/interventional studies. Ultimately, the research conducted in this theme should provide understanding and allow prediction of effects of interventions on the neuro-musculo-skeletal system (ergonomics, rehabilitation, sports, surgery, and aging).

Mechanics of musculoskeletal injury and adaptation. The primary aim of the research programme is to increase understanding of the dynamics (injury, recovery, adaptation) of the musculo-skeletal system in the light of its function as a mechanical system. The aim is not only described on the basis of a theoretical interest, but also because such increased understanding will facilitate problem-solving, with respect to issues regarding injury and adaptation of the musculo-skeletal system, in several fields of practice (e.g. ergonomics and surgery). Projects include:

Mechanical properties of muscles and muscle groups in physiological or pathological conditions:

• Muscle force-length properties
• Force transmission from muscle to intra- and extramuscular connective tissue structures in series with it.
• Mechanisms of adaptation of the, parallel and in series, number of sarcomeres in skeletal muscle.

Injury mechanisms and -probabilities in relation to task demands:

• Control of joint stability in the spine, upper extremity and knee
• Control of balance after mechanical perturbations of gait
• Effects of task demands on injury probability

Adaptation of motor control in musculoskeletal disorders:

• Changes in control of joint stability in the spin, upper extremity, and knee
• Changes in control of gait with musculoskeletal disorders after knee replacement
• Interactions of structural and control changes in Cerebral Palsy

(Patho)physiology and mechanics in human performance. The primary goal of this programme is to improve the understanding of the underlying mechanisms of optimum performance of the different organ systems relevant for human movement, how these organ systems contribute to optimum human movement performance, and how natural or clinical changes in (part of) one of more of the (sub) systems affect performance and the optimalisation of whole body performance. Projects include:

• Effects of (changing) muscular properties for neural control
• The role of energy metabolism in the qualitative and quantitative changes in neuromuscular properties during exercise (fatigue)
• The influence of chronic adaptations on neuromuscular properties and the consequences for performing during exercise
• Underlying biomechanical and physiological processes in the optimalisation of physical exercise under different boundary conditions in health, athletics and disease
• Artificial exercise in the impaired (paralysed) human movement system
• Cyclic arm work: optimising (neuro-) physiological, energetic and biomechanical performance in upper body exercise
• Mechanisms of practice, exercise, training and learning in the restoration of mobility and functioning in persons with a spinal cord injury
• Functional performance capacity in persons with lower limb impairment, especially persons with an amputation

In general, the performance of everyday perceptual-motor actions involves a high degree of coordination between the various parts of the human body as well as between limb movements and the environment. The goal of the research conduction within the theme Motor Control is to gain insight into how this functionally effective coordination comes about and how it changes adaptively in response to changes in the human motor apparatus (i.e. fatigue, injury) and the environment, as well as a result of learning, rehabilitation and ageing.

Coordination dynamics. The main goal of this programme is to gain insight into interlimb coordination and the coordination between limb movements and the environment using the formal concepts and analytical tools of dynamical systems theory. The adopted approach focuses on the stability properties of behavioural patterns and how they are affected by movement parameters (e.g., accuracy, frequency, amplitude, and force), cognitive influences and perception. If tractable, the observed properties and effects are explicitly modelled in terms of (stochastic) equations of motion to uncover the functional and operational design of motor control systems. The experimental tasks of interest range from basic laboratory tasks like rhythmic limb movements, tapping, isometric force production, reaching and pointing, to more complex behaviours like standing upright, locomotion, juggling, catching and hitting. Projects include:

• Unified dynamics of discrete and cyclical movements
• Cognitive influences on stability-related interlimb interactions
• Asymmetries in interlimb coordination
• Interlimb and intersegmental coordination during gait
• Rehabilitation in Parkinson’s disease: strategies for cueing (RESCUE)
• Functional recovery of gait and posture after stroke
• Preventions of falls in the elderly
• Functional recovery following knee replacement

Perceptual motor control: development, learning and performance. The research of this programme focuses on how perceptual-motor control at the different time scales of development, learning and peak performance is brought about by the constraints on the actor-environment system. The main objective of the current programme is to identify the relative contribution of these constraints to perceptual-motor control and their changes therein at the different time scales. The core of the research lies with the interaction between the task (e.g., object properties, task instructions) and organismic constraints (e.g., brain damage, anxiety) with special emphasis on the use of perceptual information. Projects include:

• Calibration in perception and action
• The structure of the visual workspace in object manipulation
• Environmental influences on the development of fetal movement coordination
• The information-based control of interceptive timing: a developmental perspective
• Visual timing in the context of road crossing
• Balance and walking coordination
• Visual information processing for action in complex sport tasks
• Mental skills and task focus
• Impact of state variables, particularly anxiety on movement behaviour

The biophysics and psychophysics of sensorimotor control. The general objective of this programme is to understand, for various perceptual and motor tasks, why they are performed the way they are performed, and how they are controlled. This understanding is ultimately sought for humans, but some studies are also directed at animal motion, for various reasons. Although the primary objective is to gain fundamental insights, the results are translated whenever possible into recommendations for rehabilitation programs in health care, and training programs and equipment used in sports. Projects include:

Mechanics:

• Does force rise time explain the difference in jump height between countermovement and squat jumps?
• What are the effects of skin suits on drag in swimming?
• What are the requirements on joint stiffness during human standing?
• Does length-dependent calcium sensitivity of contractile tissue enhance muscle stiffness?
• How is oscillation frequency of a freely swinging body segment affected by mass perturbation?
• What determines the optimal pedalling rate during sprint cycling?

Energetics:

• How should cycling and speed skating races be paced?
• Does high altitude training affect swimming performance?
• Can mechanical energy be coupled to metabolic energy in running?
• Does metabolic energy used in running correspond to heat production?

Control:

• How is balance in upright standing regulated?
• How is ‘leg stiffness’ regulated in hopping?
• Can mechanical power output in FES cycling be improved by releasing the ankle joint?
• How are visual cues about target orientation used in on-line control of aiming movements?
• Does visuo-motor adaptation involve sensory recalibration?
• How is gravity taken into account in the control of fast goal-directed arm movements?
• How are intersegmental forces and moments taken into account in the control of fast goal-directed arm movements?

Perception:

• How good is colour constancy in our daily environment?
• Can haptic spatial information be processed in parallel across digits?
• Does Gestalt formation help haptic perception?
• What are the temporal limitations of combining cues in visual perception?