Jaap Harlaar

Jaap Harlaar
Delft University of Technology | TU

45.02
 · 
Prof

About

298
Publications
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Publications

Publications (298)
Article
Full-text available
Background: In this systematic review we investigate which instrumented measurements are available to assess motor impairments, related activity limitations and participation restrictions in children and young adults with dyskinetic cerebral palsy. We aim to classify these instrumented measurements using the categories of the international classif...
Article
Full-text available
With the rise of biofeedback in gait training in cerebral palsy there is a need for real-time measurements of gait kinematics. The Human Body Model (HBM) is a recently developed model, optimized for the real-time computing of kinematics. This study evaluated differences between HBM and two commonly used models for clinical gait analysis: the Newing...
Article
In children with cerebral palsy (CP), rigid ventral shell ankle-foot orthoses (vAFOs) are often prescribed to reduce excessive knee flexion in stance and lower the energy cost of walking (ECW). However, how vAFOs affect ECW is a complex issue, as vAFOs may have an impact on lower limb biomechanics, upper body movements, and balance. Besides, the vA...
Article
Full-text available
Objective: To describe the orthotic properties and evaluate the effects of ankle-foot orthoses for calf muscle weakness in persons with non-spastic neuromuscular disorders compared with shoes-only. Design: Cross-sectional study. Subjects: Thirty-four persons who used ankle-foot orthoses for non-spastic calf muscle weakness. Methods: The foll...
Article
Background: Estimating muscle-tendon complex (MTC) lengths is important for planning of soft tissue surgery and evaluating outcomes, e.g. in children with cerebral palsy (CP). Conventional musculoskeletal models often represent the foot as one rigid segment, called a mono-segment foot model (mono-SFM). However, a multi-segment foot model (multi-SF...
Article
Full-text available
Background: To improve gait, persons with calf muscle weakness can be provided with a dorsal leaf spring ankle foot orthosis (DLS-AFO). These AFOs can store energy during stance and return this energy during push-off, which, in turn, reduces walking energy cost. Simulations indicate that the effect of the DLS-AFO on walking energy cost and gait bi...
Article
Objective: To evaluate muscle activation patterns and co-contraction around the knee in response to walking with modified gait patterns in patients with medial compartment knee-osteoarthritis (KOA). Design: 40 medial KOA patients walked on an instrumented treadmill. Surface EMG activity from seven knee-spanning muscles (gastrocnemius, hamstrings...
Article
Accurate assessment of the talo-crural (ankle) joint angle at physical examination is important for assessing extensibility of m. triceps surae (TS) in children with spastic cerebral paresis (SCP). The main aim of this study was to quantify foot flexibility during standardized measurements of TS muscle-tendon complex extensibility (i.e. based on fo...
Article
Full-text available
Background Children with cerebral palsy (CP) often show impaired selective motor control (SMC) that induces limitations in motor function. Children with CP can improve aspects of pathological gait in an immediate response to visual biofeedback. It is not known, however, how these gait adaptations are achieved at the neural level, nor do we know the...
Article
Background: Virtual reality presents a platform for therapeutic gaming, and incorporation of immersive biofeedback on gait may enhance outcomes in rehabilitation. Time is limited in therapeutic practice, therefore any potential gait training tool requires a short set up time, while maintaining clinical relevance and accuracy. The aim of this study...
Article
Full-text available
Comprehensive instrumented muscle and joint assessments should be considered when prescribing Botulinum NeuroToxin‐A (BoNT‐A) treatment in spastic paresis. In a child with spastic paresis, comprehensive evaluation following treatment with BoNT‐A, serial casting, and physiotherapy showed that short‐term improvements in gait occurred without changes...
Conference Paper
Full-text available
Measuring foot kinematics during gait is a great challenge because of the numerous bones in the foot. Even multi-segment foot models like the Oxford Foot Model and Rizzoli Foot Model must combine bones to describe foot kinematics. Moreover, the definition of the coordinate system attached to the segment and soft tissue artefacts will influence thes...
Conference Paper
Wearable actuators in lower-extremity active orthoses or prostheses have the potential to address a variety of gait disorders. However, whenever conventional joint actuators exert moments on specific limbs, they must simultaneously impose opposing reaction moments on other limbs, which may reduce the desired effects and perturb posture. Momentum ex...
Article
Neuro-musculoskeletal modelling can provide insight into the aberrant muscle function during walking in those suffering cerebral palsy (CP). However, such modelling employs optimization to estimate muscle activation that may not account for disturbed motor control and muscle weakness in CP. This study evaluated different forms of neuro-musculoskele...
Article
Computed tomography (CT) imaging can be used to determine bone pose, sometimes combined with skin-mounted markers. For this specific application, a lower radiation dose than the conventional clinical dose might suffice. This study aims to determine how lowering the radiation dose of a CT-scan of the ankle and foot affects the precision of detecting...
Article
Background: There are numerous static measures of foot posture but there is no published score of dynamic foot motion. Three-dimensional gait analysis can include a multi-segment foot model like the Oxford Foot Model (OFM) to comprehensively quantify foot kinematic deviations across the gait cycle but it lacks an overall score, like the Gait Profi...
Article
Background: In the process of 3D-gait analysis interpretation, gait deviations in children with cerebral palsy are identified through comparison with reference data of typically developing children (TD). Generally, TD-data are presented based on averaged normalized curves of numerous strides for different ages and walking velocities. In patients ho...
Article
Aims: For violinists, the shoulder rest is an ergonomic adaptation to reduce musculoskeletal load. In this study, we aimed to evaluate how the height of the shoulder rest affects the violin fixation force and electromyographic (EMG) activity of the superficial neck and shoulder muscles. Methods: In professional violinists, four different shoulde...
Article
This study aimed to identify critical physiological outcome variables underlying reduced upper extremity task performance in Duchenne muscular dystrophy (DMD). These critical variables were used to propose an explanatory biophysical model of the upper extremity working mechanisms in DMD. Twenty-three DMD patients (8–21 years) participated in this s...
Article
Background: Instability of the knee joint during gait is frequently reported by patients with knee osteoarthritis or an anterior cruciate ligament rupture. The assessment of instability in clinical practice and clinical research studies mainly relies on self-reporting. Alternatively, parameters measured with gait analysis have been explored as suit...
Article
Full-text available
Background: Gait retraining interventions using real-time biofeedback have been proposed to alter the loading across the knee joint in patients with knee osteoarthritis. Despite the demonstrated benefits of these conservative treatments, their clinical adoption is currently obstructed by the high complexity, spatial demands, and cost of optical mo...
Article
Background: Patients with multiple sclerosis (pwMS) often experience a decline in motor function and performance during prolonged walking, which potentially is associated with reduced ankle push-off power and might be alleviated through structured exercise. The objectives of this pilot study were to assess ankle push-off power and walking performa...
Article
Purpose The aim of this study is to determine the relationship between complaints of the neck and shoulder region, the jaw-shoulder violin fixation force, and the activity of the neck and shoulder muscles in violinists. Methods In this case-control study twenty professional violinists were included, of which ten with current complaints of the neck...
Article
Objective: To investigate the immediate response to avatar-based biofeedback on three clinically important gait parameters; step length, knee extension and ankle power, in children with cerebral palsy (CP). Design: Repeated measures design. Setting: Rehabilitation clinic. Participants: Twenty-two children with spastic paresis (10y4m±3y1m), a...
Article
Full-text available
Objective To evaluate whether improvement of proprioception, pain or dynamic knee instability mediate the effect of wearing a soft knee brace on activity limitations in persons with knee osteoarthritis (OA). Methods Exploratory analysis from 44 participants with knee OA and self‐reported knee instability in a laboratory trial evaluating the effect...
Article
Full-text available
Background: Patients with calf muscle weakness due to neuromuscular disorders have a reduced ankle push-off work, which leads to increased energy dissipation at contralateral heel-strike. Consequently, compensatory positive work needs to be generated, which is mechanically less efficient. It is unknown whether neuromuscular disorder patients compe...
Article
Objectives: Wearing a soft knee brace has been shown to reduce self-reported knee instability in persons with knee OA. There is a need to assess whether a soft knee brace has a beneficial effect on objectively assessed dynamic knee instability as well. The aims of the study were to evaluate the effect of a soft knee brace on objectively assessed d...
Article
Objective: To identify factors associated with long-term improvement in gait in children after selective dorsal rhizotomy (SDR). Design: Retrospective cohort study SETTING: University medical center PARTICIPANTS: 36 children (age 4-13y) with spastic diplegia (gross motor classification system level I (n=14), II (n=15) and III (n=7) were included...
Article
Background: The knee adduction moment (KAM) is often elevated in medial knee osteoarthritis (KOA). The aim of this study was to evaluate effects on KAM and patient-reported outcomes of a six-week gait training program. Methods: Twenty-one patients (61 ± 6 years) with KOA participated in a six-week biofeedback training program to encourage increa...
Article
Video games are increasingly used in balance rehabilitation since literature has indicated promising effects on motivation [1] and functional outcomes [2] in several patient populations. Several pilot studies investigated the effectiveness of video game-based balance-training (VGBT) in children with cerebral palsy (CPc) [3,4], as these children exp...
Conference Paper
Background Wearing a soft knee brace has been shown to reduce self-reported knee instability in persons with knee osteoarthritis (OA).¹ There is a need to assess whether a soft knee brace has a beneficial effect on objectively assessed dynamic knee instability as well. Objectives The aims of the study were: (i) to evaluate the immediate effect of...
Conference Paper
Background We have previously shown that wearing a soft knee brace reduced activity limitations in persons with knee osteoarthritis (OA).¹ Several underlying mechanisms have been proposed via which a soft knee brace reduces activity limitations in persons with knee OA.² However, to our knowledge, no study has identified mechanisms explaining this e...
Article
Objective: To evaluate i) the relationship between the knee contact force (KCF) and knee adduction and flexion moments (KAM and KFM) during normal gait in people with medial knee osteoarthritis (KOA), ii) to evaluate the effects on the KCF of walking with a modified gait pattern and iii) to evaluate the relationship between changes in the KCF and...
Article
Full-text available
To improve gait in children with spastic paresis due to cerebral palsy or hereditary spastic paresis, the semitendinosus muscle is frequently lengthened amongst other medial hamstring muscles by orthopaedic surgery. Side effects on gait due to weakening of the hamstring muscles and overcorrections have been reported. How these side effects relate t...
Article
The objective of this study was to investigate the learning process of knee osteoarthritis (KOA) patients learning to change their foot progression angle (FPA) over a six-week toe-in gait training program. Sixteen patients with medial KOA completed a six-week toe-in gait training program with real-time biofeedback. Patients walked on an instrumente...
Article
Full-text available
Abstract Background We aimed to (i) evaluate the immediate effect of a soft knee brace on pain, activity limitations, self-reported knee instability, and self-reported knee confidence, and (ii) to assess the difference in effect between a non-tight and a tight soft brace in patients with knee osteoarthritis (OA). Methods Forty-four patients with kn...
Article
Introduction: The Oxford Foot Model (OFM) is a multi-segment, kinematic model developed to assess foot motion. It has previously been assessed for repeatability in healthy populations. To determine the OFM's reliability for detecting foot deformity, it is important to know repeatability in pathological conditions. The aim of the study was to asses...
Article
Full-text available
The developmental goal of 3D ultrasound imaging (3DUS) is to engineer a modality to perform 3D morphological ultrasound analysis of human muscles. 3DUS images are constructed from calibrated freehand 2D B-mode ultrasound images, which are positioned into a voxel array. Ultrasound (US) imaging allows quantification of muscle size, fascicle length, a...
Article
Gait analysis is used for the assessment of walking ability of children with cerebral palsy (CP), to inform clinical decision making and to quantify changes after treatment. To simplify gait analysis interpretation and to quantify deviations from normality, some quantitative synthetic descriptors were developed over the years, such as the Movement...
Article
Background: Gait modifications can reduce the knee adduction moment, a representation of knee loading. Reduced loading may help to slow progression of medial knee osteoarthritis. We aimed to investigate the response of patients with medial knee osteoarthritis to direct feedback on the knee adduction moment as a method for modifying the gait patter...
Article
Knee instability is a major problem in patients with anterior cruciate ligament injury or knee osteoarthritis. A valid and clinically meaningful measure for functional knee instability is lacking. The concept of the gait sensitivity norm, the normalized perturbation response of a walking system to external perturbations, could be a sensible way to...
Conference Paper
Background The Animated Activity Questionnaire (AAQ) measures activity limitations in hip and knee osteoarthritis (HKOA), and was developed in close collaboration with patients¹. Previously we showed an adequate construct- and cross-cultural validity of the AAQ² Objectives To determine the reliability, responsiveness and interpretability of the AA...
Article
Background and purpose: To support clinical decision-making in central neurological disorders, a physical examination is used to assess responses to passive muscle stretch. However, what exactly is being assessed is expressed and interpreted in different ways. A clear diagnostic framework is lacking. Therefore, the aim was to arrive at unambiguous...
Article
Full-text available
Background Therapeutic management of upper extremity (UE) function of boys and men with Duchenne Muscular Dystrophy (DMD) requires sensitive and objective assessment. Therefore, we aimed to measure physiologic UE function of healthy subjects and DMD patients in different disease stages, and to evaluate the relation between these physiologic measure...
Article
Full-text available
Introduction In patients with neuromuscular disorders and subsequent calf muscle weakness, metabolic walking energy cost (EC) is nearly always increased, which may restrict walking activity in daily life. To reduce walking EC, a spring-like ankle-foot-orthosis (AFO) can be prescribed. However, the reduction in EC that can be obtained from these AFO...
Article
Background: Knowledge on lower extremity strength is imperative to informed decision making for children with cerebral palsy (CP) with mobility problems. However, a functional and clinically feasible test is not available. We aimed to determine whether the squat test is suitable for this purpose by investigating test performance and execution in c...
Article
Full-text available
Background: Increased resistance in muscles and joints is an important phenomenon in patients with cerebral palsy (CP), and is caused by a combination of neural (e.g. spasticity) and non-neural (e.g. contracture) components. The aim of this study was to simulate instrumented, clinical assessment of the hamstring muscles in CP using a conceptual mo...
Article
Full-text available
To increase knee range of motion and improve gait in children with spastic paresis (SP), the semitendinosus muscle (ST) amongst other hamstring muscles is frequently lengthened by surgery, but with variable success. Little is known about how the pre-surgical mechanical and morphological characteristics of ST muscle differ between children with SP a...
Data
Data. Supplementary table containing all individual data from which the summary data are presented in the manuscript. Absolute data as well as normalized data are included in the supplementary table. (XLSX)
Article
Real-time feedback may be useful for enhancing information gained from clinical gait analysis of children with cerebral palsy (CP). It may also be effective in functional gait training, however, it is not known if children with CP can adapt gait in response to real-time feedback of kinematic parameters. Sixteen children with cerebral palsy (age 6–1...