Title Promoter Affiliations Abstract "Naar een beter begrip van onderliggende mechanismen van verminderde controle van de dynamische balans na een beroerte middels een combinatie van experimenten en computermodellen." "Friedl De Groote" "Human Movement Biomechanics Research Group, Research Group for Neurorehabilitation (eNRGy)" "Ieder jaar krijgen meer dan 10,000 mensen in België een beroerte (cerebrovasculair accident, CVA), wat leidt tot een verlaagde kwaliteit van leven door verminderde mobiliteit en sociale isolatie.Een CVA is een (sub)corticale laesie, veroorzaakt door een propje (ischemische CVA) of een gescheurd bloedvat (bloederig CVA).Ambulante CVA-patiënten hebben vaak moeite met het bewaren van hun balans tijdens staan en stappen, doordat de centrale laesies leiden tot verminderde coördinatie van bewegingen, spierfunctie en sensorische functie.Deze problemen maken CVA-patiënten instabiel en minder bestand tegen verstoringen van de balans.Hoewel balans en stap-training na CVA constant geïnnoveerd wordt, is de uitkomst van behandelingen erg variabel en tevens al decennia gestagneerd, mogelijk door een gebrek aan begrip van de onderliggende mechanismen van de balans en stap problemen na CVA.Neuromusculoskeletale predictieve simulaties kunnen ons dit inzicht verschaffen, door beoordeling van de geïsoleerde effecten en interacties van elk mechanisme (e.g. verminderde coördinatie van bewegingen, spierfunctie en sensorische functie).In dit project gaan we daarom neuromusculoskeletale modellen ontwikkelen om predictieve simulaties van dynamische balans controle tijdens het lopen na CVA te maken.Daarnaast ontwikkelen we proof-of-concept voor een simulatie platform dat behandeluitkomst na CVA voorspelt, door een simulatie framework te ontwikkelen dat het effect voorspelt van AFO-gebruik op dynamische balans na CVA." "Neo-Ottomanism? New Strategies of Turkey and the Impact of Foreign Aid to Post-War Cultural Reconstruction in the Balkans." "Peter Vermeersch" "Leuven International and European Studies (LINES)" "This project seeks to find out how foreign assistance in the fields of culture, religious revival and education change regions ravaged by inter-ethnic violence and state breakdown, and how such foreign assistance is perceived locally. My case study is the assistance provided from the Turkish Republic to Bosnia-Herzegovina, and local responses to it. The empirical research will focus on Turkish aid in the areas of higher education, religious studies, and the rebuilding of Ottoman-era monuments. This project sets the analysis of the impact of Turkish aid in the Balkans in the context of the revival of the concept and debates on Neo-Ottomanism in the region and globally. The analysis poses following questions: How do the interpretations of the historical legacy of the Ottoman Empire in the post-Yugoslav region correspond with actual policies of aid that the Republic of Turkey provides as a major donor, especially for postwar reconstruction projects in Bosnia-Herzegovina? What sort of changes in the political and popular culture in the beneficiary country can we observe as a result of Turkish aid in the areas of culture, higher education and religious education, according to local responses in Bosnia-Herzegovina? What is the interaction between the fears of Neo-Ottomanism as an alleged expansionist and ‘Islamization’ program of Turkey in the Balkans and the anti-Turkish, anti-Muslim discourses as a recent characteristic of the populist rhetoric in several European Union states?" "Conflicting frames of reconciliation: the politics of peacebuilding in the Balkans." "Leuven International and European Studies (LINES)" "In order to rebuild peace successfully in a society that has been ravaged by (ethnic) conflict, it is commonly understood that the former warring parties should reconcile or engage in practices of reconciliation. However, it is not always clear what reconciliation precisely entails, and definitions of the concept often vary or remain vague. Some authors have tried to remedy this by proposing more concrete definitions or new ideal models of reconciliation. This project moves beyond this theoretical discussion by examining the practice of reconciliation and more precisely the definitions and frames of reconciliation used by practitioners in the field. We study the case of the former Yugoslavia, where a group of NGOs is currently working together to press politicians to establish a Truth and Reconciliation Commission (the RECOM initiative). This project investigates the ways in which three sets of actors (civil society at large, RECOM, and political elites) in three countries (Serbia, Croatia and Bosnia-Herzegovina) frame reconciliation. Our aim is to unearth the different meanings actors attribute to reconciliation and the tensions this ‘politics of signification’ causes in the relationships between them. Rather than seeing reconciliation simply as something that is either present or not, we open up the ‘black box’ of reconciliation and gain an understanding of the discursive and dynamic processes leading to changing interaction patterns between (former) adversaries." "BOF 2008: Short stay Dr. Balazs Hajgato" "Michael DELEUZE" "Center of Molecular and Materials Modelling" "BOF 2008 - Short Stays - Professor Doctor Michael Deleuze. On August 25, 2008, the Research council has the stay of Dr Balazs Hajgato approved. During this stay Doctor Hajgato will perform research in collaboration with professor doctor Michael Deleuze in the research group Theoretical Chemistry." "Balance control in young children: a synergistic approach combining functional assessment and neuromechanics to unravel balance control mechanisms." "Ann Hallemans" "Movement Antwerp (MOVANT)" "Adequate balance control is a prerequisite to achieve postures in early life and more complex gross and fine motor skills later in childhood. Balance deficits are a common problem in children with various pathologies such as cerebral palsy, developmental coordination disorder or sensorineural hearing loss. Because of the potential impact of these balance deficits on motor development, they need to be detected early in childhood. However, balance control is complex and comprises different mechanisms such as predictive, proactive and reactive control. At present none of the available paediatric balance tests comprehend to total concept of balance control. Most tests have been focussing on balance control in static and predictable environments, ignoring the contribution of reactive balance mechanisms. This is an underrepresentation of the daily life situation involving object interactions and changing physical environments. Therefore, the aim of this project is to develop an integrated approach of assessing balance in 5 to 7 year old children covering the entire concept of balance control. A synergistic approach, combining functional assessment methods of balance performance with more in-depth neuromechanical analysis will be used. Neuromechanics focusses on the interplay between the neural processes (e.g. reaction times) and the mechanical aspects of balance control (e.g. amount of sway) unravelling balance control strategies that might otherwise remain hidden. In this way, fundamental insights will be gained into the construct of balance control and the contribution of the different mechanisms in 5 to 7 year old children. These insights will result in a validated test that allows the clinician to identify overall balance deficits as well as the specific domains of balance control that are disturbed. Identification of these domains allows for specific physiotherapeutic intervention planning. Furthermore, the better understanding of balance control mechanisms in young children will open new horizons for research regarding the contribution of balance control deficits to developmental (motor) problems in children." "A Decision Support System incorporating a validated patient-specific, multi-scale Balance Hypermodel towards early diagnostic Evaluation and efficient Management plan formulation of Balance Disorders (EMBalance)." "Floris Wuyts" "Lab for Equilibrium Investigations and Aerospace (LEIA)" "The EMBalance project aims to extend existing but generic and currently uncoupled balance modelling activities leading to a multi-scale and patient-specific balance Hypermodel, which will be incorporated to a Decision Support System, towards the early diagnosis, prediction and the efficient treatment planning of balance disorders. Various data will feed the intelligent system increasing the dimensionality and personalization of the system. Human Computer Interaction techniques will be utilized in order to develop the required interfaces in a user-intuitive and efficient way, while interoperable web-services will enhance the accessibility and acceptance of the system." "Balkan GEO Network - Towards Inclusion of Balkan Countries into Global Earth Observation Initiatives" "Robert De Wulf" "Department of Forest and water management, University of Montenegro, Joanneum Research, Irida Labs (Greece), University of Novi Sad, Romanian Space Agency, National Institute of Geophysics, Geodesy and Geography, Polytechnic University of Tirana, Jozef Stefan Institute, Environment Agency Austria, International Institute for Applied Systems Analysis, University of Split, Geonardo (Hungary), University of Sarajevo" "This project aims to identify existing EO-data providers and users in the wider Balkan region, to determine their status, potentials and needs, and to coordinate EO players by establishing proper interfaces and networking between them. A broad analysis of gaps and complementarities of EO activities within the region will be performed, with the emphasis on user needs in the specific context of the Balkan region" "A blended experimental and computational approach to assess control of standing balance" "Friedl De Groote" "Human Movement Biomechanics Research Group" "With age, our ability to complete seemingly simple activities of daily living declines. Older adults move slower, less accurate and more often lose their balance resulting in frequent falls, which might lead to significant injuries requiring medical attention and leading to loss of independence. Age is associated with declines in muscle strength, sensory acuity, motor acuity and cognitive ability, but our understanding of the relative contribution of these different neural and muscular changes in sensorimotor function to reduced balance control is incomplete. This hampers the design and selection of prevention and rehabilitation therapies and devices that aim to maintain or restore efficient balance control in order to prevent falls.The combination of experimental data and model-based simulations has much potential to advance our understanding of the mechanisms underlying balance control. Such blended experimental-computational approach has mainly been applied to study the relation between muscular and skeletal properties and movement, but has been used less to study how limitations in the central nervous system affect human movement coordination. The efficient and accurate integration of sensory feedback signals by the central nervous system is key to perform skillful movement but is always imperfect and seems to deteriorate as we age.The main aim of this thesis was to identify how different age-related changes in the neuro-musculoskeletal system affect reactive balance performance, and how resistance and perturbation training, an established and novel intervention respectively, improve balance control. This overall goal was tackled using a blended experimental-computational approach. Experiments involved a protocol, quantifying balance performance, strength, sensory acuity and motor acuity in both young and older adults. This allowed testing associations between sensorimotor function and reactive balance performance. Experiments were complemented with optimal control simulations based on neuro-musculoskeletal models and were applied to test whether the experimentally established associations might be causal. Four studies were executed to accomplish the overall goal.In study 1, we developed a new simulation framework that extends currently available frameworks to incorporate sensory noise, motor noise and other types of uncertainty that affect human movement. The presented framework is novel compared to prior simulation approaches as it allows for simulations of systems that are both stochastic and nonlinear. Such an approach was previously only available for simple musculoskeletal models that neglected important features of muscle physiology and nonlinearities in the skeletal dynamics because of limitations in numerical efficiency. Incorporating uncertainty in human movement simulations is important to accurately study the neural control of movement and the limitations related to balance control.Our new approach combines recent advances in deterministic simulations of human movement with an approximate reformulation of the stochastic simulation problem into a deterministic form. We successfully applied the new framework to generate more accurate and detailed predictions of both standing balance and goal-directed reaching, which we chose as paradigm movement tasks since they are widely studied. We demonstrated that both accurate musculoskeletal representations and physiological noise contribute to the realism of movement predictions. The presented stochastic optimal control framework allowed simulating more realistic movement patterns and neural control laws compared to previously available simulation approaches. Neural control was more accurately simulated by (1) accounting for uncertainty with Gaussian properties, to represent sensory and motor noise or unpredictable interactions with the simulated environment, (2) allowing contributions from both sensorimotor feedback and feedforward controls to movement and (3) enabling the identification of minimum effort solutions under explicit movement accuracy and stability constraints. By increasing the fidelity of neuro-musculoskeletal simulations, we predicted and investigated features of human movement that have been difficult or impossible to study with available simple stochastic models or simulations based on complex deterministic models.In study 2, we aimed to understand the origins of trial-by-trial (intra-subject) and between-subject (inter-subject) variability in reactive balance responses to platform translations during standing. Reactive balance responses exhibit much intra- and inter-subject variability, which is not well understood. Such variability complicates studying the effect of aging and interventions. A better understanding of intra- and inter-subject variability in healthy young adults will allow better differentiation between groups. We collected the responses of ten young healthy adults to unpredictable platform translations and performed simulations to test for potential causality.Under the instruction to try and keep the feet in place, the responses to unpredictable platform translations exhibited a continuum of center of pressure strategies (COP strategies), i.e. single pendulum-like rotation around the ankle joint, hip strategies, i.e. counter rotation of leg and trunk segments, and stepping strategies in response to the perturbations. First, our experiments and simulations confirmed that initial posture explains the experimentally observed trial-by-trial variability with a more anterior initial COM position increasing the use of the hip strategy. Second, differences in task-level goal explain observed inter-subject variability with prioritizing effort minimization leading to COP strategies and prioritizing stability leading to hip strategies. Third, interactions between initial posture and task-level goal explained observed differences in intra-subject variability across subjects. Based on these results we formulated outcome measures that normalized for trial-by-trial differences in initial posture, and in turn allowed for better differentiation between groups in later studies.In study 3, we compared the effectiveness of perturbation and resistance training for reactive balance performance during standing and analyzed the mechanisms through which such training could improve reactive balance performance in different movement tasks. Based on the experimentally determined associations between strength and reactive balance performance, resistance training has been a popular fall prevention therapy. However, such interventions have at most resulted in limited improvements in balance performance. Perturbation training is a more recent training paradigm with some promising results but has not been compared to resistance training in terms of effectiveness to improve reactive balance performance. In addition, the adaptations in balance-correcting mechanisms that underlie improvements in reactive balance control after perturbation and resistance training are not well understood. Moreover, it is unclear whether perturbation and resistance training induce adaptations in balance control that generalize to movement tasks that were not part of the training. We performed two training interventions with two groups of healthy older adults: a 12-week resistance training intervention and a 3-week perturbation training intervention consisting of support-surface perturbations of standing balance. Reactive balance performance during standing and walking as well as a set of neuro-muscular properties were assessed pre- and post-intervention.Both perturbation training and resistance training induced training specific improvements. Perturbation training was more effective in reducing step incidence during perturbations of standing than resistance training. Resistance training increased maximal strength of the knee extensors whereas perturbation training did not. Following perturbation training, older adults were able to suppress the initiation of a step at higher deviations from upright equilibrium without adaptation in the application of COP and hip strategies. Improvements in reactive balance during standing induced by perturbation training did not generalize to perturbed walking or dynamic balance performance during narrow-beam walking, indicating the specificity of such training interventions and suggesting that different mechanisms drive the selection of a strategy during both tasks.In study 4, we sought to identify the cause-effect relations between age-related changes in sensorimotor function and reactive balance performance. Many factors of the neuro-musculoskeletal system change with age but our understanding of the relative contribution of these different neural and muscular changes in sensorimotor function to reduced balance control is incomplete. Here we collected a comprehensive dataset to associate vestibular function, proprioceptive function, visual function, sensory reweighting ability, strength and motor accuracy with balance performance across both young and older adults. Next, we tested whether the detected associations might reflect causal relations by applying the novel simulation framework of study 1.Older adults stepped more often in response to platform translations during standing compared to younger adults, indicating their decreased balance performance. We found that stepping threshold, but not the reliance on hip or COP strategies was associated with step incidence. The increased step incidence was associated with experimental measures of strength, visual acuity and the sensory organization test preference score, which quantifies the ability to suppress conflicting sensory information. Yet, only the sensory organization test preference score correlated with the stepping threshold. Using stochastic optimal control simulations we estimated parameters describing sensory and motor noise in our neuro-musculoskeletal model, which we used in predictive simulations of reactive balance responses to platform translations. Assuming optimal sensory reweighting, our simulations suggested that older adults can compensate for both increasing visual and vestibular noise to maintain reactive balance performance in response to support-surface translations. In simulation, decreased strength limited the efficiency of the COP strategy, which would induce increased step incidence for the highest perturbation magnitudes, but we did not observe age-related changes in the COP strategy in experiments.  Therefore, it remains unclear whether strength might have contributed to limited reactive balance performance in our group of older adults. Taken together, our blended experimental-computational approach suggest that healthy older adults may be able to adapt to alterations in sensory and motor noise, but that they may lack the ability to rapidly adjust their balance control strategy to a different context. A different context refers to a different movement task (e.g. standing and walking) or a different type of perturbation during the same task (e.g. platform translations vs platform rotations or translations in different directions). Further modeling developments are needed to capture the ability to adjust balance control to different contexts, which was measured here by the sensory organization test preference sub scores.The blended experimental-computational approach applied in this dissertation generated new insights specific to reactive balance control in aging populations. Although experimental measures of strength and sensory acuity on the one hand and reactive balance performance on the other hand are associated, it seems that healthy older adults may be able to compensate for such decreases in sensorimotor function. We propose that rather abilities that determine whether individuals can flexibly adjust sensorimotor responses to different movement contexts limit reactive balance performance in older adults. We demonstrated that such abilities might be improved following perturbation training, where  an increase in the ability to suppress stepping responses to unpredictable multidirectional perturbations, without changes in the application of COP and hip strategies, led to improved reactive balance performance. Future therapeutic approaches might benefit from increasing focus on applying balance perturbations that challenge balance throughout different contexts and require different motor corrections by for example combining perturbations in different directions or combining balance tasks with another task (dual task training).The combination of collected data on sensorimotor function with simulations of musculoskeletal models that incorporated the effects of uncertainty is innovative and might be useful to address more unanswered research questions on the limitations of human movement due to constraints in both the neural and musculoskeletal system and to develop interventions and devices to alleviate such limitations." "Towards Optimized Virtual Reality Interventions for Improving Balance and Muscle Strength in Healthy Elderly" "Sabine Verschueren" "Research Group for Musculoskeletal Rehabilitation, Human Movement Biomechanics Research Group" "SummaryIndependence at older age is compromised on a large scale by fall-related injuries. About 40% of those aged 65 and older, fall at least once per year. The high incidence of falls is attributable to risk factors such as age-related decreases in postural control and muscle strength. However, balance training programs can improve postural control and muscle strength and thereby reduce the risk of falls. Challenging weight shifts and muscle activation have shown to be important components of training programs that aim to reduce fall risk. Virtual Reality (VR) balance training may have advantages over regular exercise training in older adults. However, results so far are conflicting, potentially due to the lack of challenge imposed by weight shifts and muscular engagement in those VR training applications. The main aim of this research project was to design and test new VR training games for balance and muscle training in the elderly that optimally exploit age- specific movement requirements to challenge balance and muscle activation, as well as user requirements to increase intrinsic motivation.In chapter one we conducted a systematic review to study the effectiveness of different VR-training interventions in improving balance in healthy elderly, and to investigate whether the balance challenge of VR-training has been assessed. A computer aided search of the databases PubMed, Web of Science and Cinahl was performed until August 2015, to identify RCTs that studied the effectiveness of VR-balance-training in healthy elderly. The systematic search resulted in 41 articles, of which 26 were RCTs. Most common outcome measures were the timed up and go,Berg balance scale and a battery of force plate measures. The results and effect sizes of different studies showed large variability but mean change scores rarely exceeded minimal detectable change. Studies analyzing the balance challenge imposed by the training were missing. An improved understanding of the balance challenge in different types of games is needed to adequately select and prescribe them in the context of balance training programs and fall prevention tools.To investigate the challenge imposed on balance in VR balance games, the study in chapter two assessed to which extent two similar skiing games induce challenging weight shifts, as reflected in center of mass (COM) movements relative to participants’ functional limits of stability. The functional limits of stability (FLOS) represent the limits to which individuals can move their COM without the need to take a step. Thirty young and thirty elderly participants performed two skiing games, one on the Wii Balance board (Wiiski), which uses a force plate, and one with the Kinect sensor (Kinski), which performs motion tracking. The effect of the games, age groups and the progression over trials on COM displacement were tested with Generalized Estimated Equations. The results show that in all directions with anterior and medio-lateral, but not with a posterior component, subjects showed significantly larger maximal COM displacements during the Kinski game than during the Wiiski game. Furthermore, it was shown that during the skiing games young subjects quickly learned that they did not have to move their COM much in order to be successful in the game, whereas elderly did not show such a quick decrease in COM displacements. Moreover, elderly moved more in posterior directions whereas young subjects moved more anteriorly. These findings might be related to the game incentives, since posterior displacements slowed the game down, and anterior displacements speeded the game up. For the older participants, the game speed was more likely to be experienced as too fast than too slow. As a result, elderly moved their COM posteriorly to slow down the game. By appropriately adapting the settings of the games to the skills of the participants, such a quick decline in COM displacements might be prevented. These results emphasize the importance of assessing the movement challenge in games used for balance training. Similar games impose different challenges due to the controllers and their gain settings. In conjunction with game mechanics, controllers and their gain settings determine the movements that are elicited by the games.Muscle weakness is another important risk factor for falls in elderly. In chapter three, the intensity and duration of muscle activity in Virtual Reality balance games was assessed. To this end, thirty young and thirty healthy elderly subjects played seven different VR balance games. Muscle activity of the m.Vastus Lateralis, m.Vastus Medialis, m.Soleus and m.Gluteus Medius was obtained using surface EMG. The processed EMG signals were divided in 200ms blocks, after which each block was categorized by its average normalized EMG activity i.e. >80%, 60-80%, 40-60% or 40% MVC, to identify prolonged muscle activity. We found that muscle activity during these VR training games was mostly below 40% MVC and prolonged activation was lacking. Although the activation levels during these VR games were low in general, faster movements could potentially provide a strength-training stimulus when longer activity bouts with more repetitions are included.To be able to adjust VR training as to optimally benefit from improved motivation in VR training, we need to evaluate which games and underlying game mechanics are considered motivating by older adults. In chapter four, we studied 30 elderly who played eight different VR-training games, and afterwards filled out the Intrinsic Motivation Inventory (IMI). Differences in intrinsic motivation between games were analyzed using Friedman’s ranked ANOVAs. In addition, depth interviews were conducted according to the laddering technique, to unveil the underlying game mechanics that players preferred. Overall, IMI scores were relatively high for all games, indicating that these VR games might be effective for increasing intrinsic motivation. Wii yoga and Kinect Adventures were the best scoring games on all IMI subscales. Both games provided regular positive feedback. An important game mechanic was Variation, which showed a strong link to important values such as: Stay Focused, Improve Fitness and Health and Independency. Furthermore, the game mechanics Visual Feedback and Positive Feedback, which lead to an increased Drive to Perform, were perceived valuable. Seemingly contradicting, but both important attributes such as Speed versus Slow Movements, emphasize the importance of designing VR training that adapts to the skill level of the player. We have shown that games with different game mechanics can induce high intrinsic motivation. When designing or selecting VR balance training games for elderly, these game mechanics should be incorporated to optimize a positive user experience and increase intrinsic motivation.Finally, novel VR balance games that are controlled with off-the-shelf hardware were developed based on the findings in previous chapters and recommendations for conventional training to prevent falls in healthy elderly. In chapter five the challenge in our novel VR balance games was evaluated. More specifically, we studied to which extent these games elicited challenging weight shifts and muscle activity, by evaluating muscle activity blocks and COM displacements relative to the participants’ functional limits of stability. Furthermore, the potential motivational pull of the VR training was evaluated by administering the intrinsic motivation inventory. Sixteen healthy elderly were recruited to play the novel games and two reference games that were found to be the most challenging ones for inducing muscle activity, or weight shifts in previous studies. The results show that we succeeded in creating motivating balance games that successfully challenged participants to elicit challenging weight shifts, by setting the game parameters to the functional limits of stability of each player. Our novel VR balance games induced COM displacements that resulted in medians of around 80% of FLOS or higher for all directions. Furthermore, the COM displacements in our novel games were larger for each direction compared to the reference game, although for Slingshot the left direction only reached significance at the third trial. Additionally, we improved the elicitation of consecutive muscle activity, by introducing long bouts of exercises, but it seems hard to elicit high intensity muscle activity through unloaded VR training.We conclude that affordable hardware can be effectively used to create challenging and enjoyable VR training programs. VR training programs that are optimized to elicit challenging weight shifts and muscle activity should be further studied in longitudinal interventions. These longitudinal interventions should uncover the effects of optimized VR training on balance, muscle performance and eventually the reduction of fall risk in healthy elderly.However, further research is needed to study the effect of optimized VR balance games that are developed and thoroughly tested to meet the requirements for effective training, of muscle strength, balance performance and finally a reduction of fall risk.Overall, this thesis contributes to a better understanding of how different VR training concepts can be used to optimally exploit age-specific movement requirements to challenge balance and muscle activation, as well as user requirements to increase intrinsic motivation." "The effect of spasticity on reactive balance in children with cerebral palsy" "Friedl De Groote" "Human Movement Biomechanics Research Group, Research Group for Neurorehabilitation (eNRGy), Emory University School of Medicine" "Cerebral palsy (CP) is the most common cause of physical disability in children. CP is caused by a non-progressive lesion to the developing brain. The resulting inability to selectively control muscles, reflex hyper-excitability, and muscle weakness leads to gait and balance impairments. Children with CP have deficits in reactive balance control, which is defined as the ability to maintain balance after an unpredictable disturbance. Reactive balance is needed in daily gross motor skills such as walking. Therefore, it is not surprising that 35% to 55% of the children with CP fall daily. Joint hyper-resistance is the most common symptom in CP and is clinically characterized by increased resistance to imposed joint rotation. When clinically assessing joint hyper-resistance, muscles of a relaxed patient are stretched by an imposed joint rotation with the purpose of assessing resistance. Yet, similar muscle stretches occur on a daily basis during functional movements such as walking on uneven terrain or standing on a departing bus. Therefore, joint hyper-resistance might contribute to balance impairments that are common in CP but surprisingly little is known about the mechanisms by which joint hyper-resistance affects balance control. Hence, the overall goal of this thesis was to define the contribution of joint hyper-resistance to balance impairments in children with CP. This will improve our ability to dissociate the various ways that balance can be impaired in CP and might thereby improve treatment selection.We collected experimental evidence for a novel hypothesis about the mechanisms underlying joint hyper-resistance, i.e., the important role of muscle SRS due to increased muscle tone in CP and its interaction with hyper-reflexia. We then developed a neuromechanical model capturing our novel mechanistic understanding to identify subject-specific neural and non-neural contributions to joint hyper-resistance. Next, we investigated sensorimotor transformations underlying reactive standing balance. We found that responsive muscle activity in children with CP can be explained by CoM kinematics feedback as in TD children but that both agonistic and antagonistic muscles are more sensitive to CoM disturbances, which is reflected in higher muscle responses and more co-activation. We found that increased co-activation was also present when increased joint stiffness was not useful to stay upright, suggesting that this is not a compensation strategy but a consequence of the underlying motor control impairments. We found that reduced reciprocal inhibition observed during isolated joint rotations was associated with increased muscle co-activation during reactive standing balance, whereas the neural response to stretch during isolated joint rotations was not associated with higher muscle responses during reactive standing balance. Those suggests that reduced reciprocal inhibition contributes to reactive balance impairments in children with CP whereas the role of stretch hyper-reflexia is less clear. Our preliminary results indicate that children with CP can learn to suppress muscle co-activation and to improve balance control through perturbation training. Our insights are clinically important because they can be translated into improved clinical assessments of joint hyper-resistance. First, evaluating the effect of pre-movement during clinical tests of spasticity might help distinguishing the contribution of neural and non-neural factors. Second, combining existing clinical assessments of joint hyper-resistance with our novel model-based approach to identify the underlying origins might improve diagnosis. Third, agonist-antagonist co-activation during passive joint rotations as applied in clinical tests of joint hyper-resistance might predict balance impairments. Our results also suggest that training should target the reduced reciprocal inhibition, e.g., by rotational perturbations where increased co-activation will hinder performance."