Jacques Duysens

• MD, PhD
• Professor at KU Leuven

Clinicians require quantitative measures of functional movement to inform care decisions for persons with Parkinson’s disease (PWPs). To address this need, we developed the Parkinson’s Disease—Functional Movement Battery (PD-FUNC), which includes valid items from existing assessments and evaluates five key areas from the MDS-UPDRS-III: manual dexte...

Background Generalized Joint Hypermobility (GJH) offers flexibility that could enhance motor activities. However, if it leads to injury and pain, it increases functional difficulties and activity limitations. The far-reaching consequences of activity limitations and restricted participation include poor physical fitness and diminished quality of li...

Background Joint hypermobility provides flexibility and is known to enhance motor performance but can also give rise to musculoskeletal complaints. There is evidence that young people are more flexible than older individuals, and females are more flexible than males. However, information about age- and sex-related changes in the range of motion (RO...

Clinicians require quantitative measures of functional movement to inform care decisions for persons with Parkinson’s disease (PWPs). To address this need, we developed the Parkinson’s Disease - Functional Movement Battery (PD-FUNC), which includes valid items from existing assessments and evaluates five key areas from the MDS-UPDRS-III: manual dex...

To investigate differences in proprioception using four proprioceptive tests in children with and without hypermobility. Additionally, it was tested if the results on one proprioceptive test predict the results on the other tests. Of the children (8-11years), 100 were classified as normal mobile (Beighton score 0–4) and 50 as hypermobile (Beighton...

Background Generalized Joint hypermobility (GJH) is predominantly non-symptomatic. In fact, individuals with joint flexibility usually perform better than their non-hypermobile counterparts during physical activities. Notwithstanding, strength and balance are essential to maintain the control of the extra range of motion during activities and to pr...

Freezing as seen from the inside In this viewpoint, based on personal experience, it is argued that freezing in PPD (People with Parkinson) can have a beneficial effect, as it can prevent that subjects perform actions that are beyond their capabilities. Fighting against freezing can be counterproductive and even lead to falls. Instead it is import...

Background: The purpose of this study was to determine the prevalence of hypermobility in randomly selected healthy children, without previous trauma or disease process affecting the joints and whether other demographic variables (age, sex, BMI) had an impact on Beighton scores and range of motion (RoM) in children between 6 and 10 years of age....

Eight healthy subjects walked on a treadmill at 1.25 m/s. Gait was perturbed unexpectedly by forward pushes or backward pulls at various phases in the gait cycle, of equal magnitude. Vertical ground reaction force, centre of pressure, and electromyography from 14 muscles were recorded. According to the inverted pendulum model, A-P perturbations mig...

Different levels of sleep restriction affect human performance in multiple aspects. However, it is unclear how sleep deprivation affects gait control. We applied a paced gait paradigm that included subliminal rhythm changes to analyze the effects of different sleep restriction levels (acute, chronic and control) on performance. Acute sleep deprivat...

Purpose: Human sensory and motor systems deteriorate with age. When walking, older adults may therefore find it more difficult to adjust their steps to new visual information, especially considering that such adjustments require control of balance as well as of foot trajectory. Our study investigates the effects of ageing on lower limb responses t...

This chapter discusses the importance of basic and clinical science for the rehabilitation of patients with stroke or SCI (spinal cord injury). Examples are given from novel approaches in rehabilitation. Insights can be obtained by investigating normal locomotor or postural activity but it is argued that the use of more challenging locomotor tasks...

In 1836, English physician Marshall Hall in his lectures on the nervous system posited that proprioception, vestibular function, and vision underlie postural control. In 1851, German physician Moritz Heinrich Romberg observed that patients suffering from tabes dorsalis lost their balance when they stood with eyes closed, giving rise to the Romberg...

Not necessary for this section.

Key points Goal‐directed arm movements can be adjusted at short latency to target shifts. We tested whether similar adjustments are present during walking on a treadmill with shifting stepping targets. Participants responded at short latency with an adequate gain to small shifts of the stepping targets. Movements of the feet during walking are cont...

Purpose Many falls in older people occur after tripping or slipping, mainly due to unsuccessful vertical clearances or horizontal distances. A first fall may be explained by several factors related to aging and can be a trigger to subsequent falls. It is unclear if a history of fall changes the kinematics of obstacle crossing, increasing the risk o...

If the surrounding of a visual target unexpectedly starts to move during a fast goal-directed hand movement, the hand reflexively moves along with it. This is known as the ‘manual following response’. One explanation for this response is that it is a compensation for inferred self-motion in space. Previous studies have shown that background motion...

Background: Children with Generalized Joint Hypermobility (GJH) have been reported to have poorer proprioception than children with normal mobility. However, they were usually tested under unloaded conditions and in an age-group in which pain starts to play a role. Research question: In contrast, some young children with GJH perform well in moto...

Introduction: This study investigated the effect of operative claw toe correction with release of the metatarsophalangeal (MTP) joint, repositioning of the plantar fat pad and resection of the proximal interphalangeal joint on foot kinematics, plantar pressure distribution and Foot Function Index (FFI). Methods: Prospective experimental study wi...

Following unpredictable large-magnitude stance perturbations diverse patterns of arm and leg movements are performed to recover balance stability. Stability of these compensatory movements could be properly estimated through qualitative evaluation. In the present study, we present a scale for evaluation of compensatory arm and leg movements (CALM)...

Biological motion control paradigms can be analyzed from a control theory point of view and translated to control applications. This paper revises and updates important aspects about the neural control of biped gait based on the Central Pattern Generator (CPG)and provides a controller view, including possible artificial implementations of these con...

[This corrects the article DOI: 10.3389/fneur.2018.00986.].

People can quickly adjust their goal-directed hand movements to an unexpected visual perturbation (a target jump or background motion). Does this ability decrease with age? We examined how aging affects both the timing and vigor of fast manual and postural adjustments to visual perturbations. Young and older adults stood in front of a horizontal sc...

In the present experiments, multiple balance perturbations were provided by unpredictable support-surface translations in various directions and velocities. The aim of this study was to distinguish the passive and the active phases during the pre-impact period of a fall. It was hypothesized that it should be feasible if one uses a specific quantita...

This paper provides an update on the neural control of bipedal walking in relation to bioinspired models and robots. It is argued that most current models or robots are based on the construct of a symmetrical central pattern generator (CPG). However, new evidence suggests that CPG functioning is basically asymmetrical with its flexor half linked mo...

The original publication of this paper contained an error. The background motion speeds were actually 20 and 60 cm/s instead of the 2 and 6 cm/s mentioned in the paper (also in figures). It does not affect any of the results, interpretation or conclusion.

Stable gait requires active control of the mediolateral (ML) kinematics of the body center of mass (CoM) and the base of support (BoS) in relation to each other. Stance leg hip abductor (HA) muscle spindle afference may be used to guide contralateral swing foot placement and adequately position the BoS in relation to the CoM. We studied the role of...

When reaching towards an object while standing, one’s hand responds very quickly to visual perturbations such as the target being displaced or the background moving. Such responses require postural adjustments. When the background moves, its motion might be attributed to self-motion in a stable world, and thereby induce compensatory postural adjust...

Humans can navigate through challenging environments (e.g., cluttered or uneven terrains) by modifying their preferred gait pattern (e.g., step length, step width, or speed). Growing behavioral and neuroimaging evidence suggests that the ability to modify preferred step patterns requires the recruitment of cognitive resources. In children, it is ar...

During walking our balance is maintained by muscle action. In part these muscle actions automatically respond to the imbalance. This paper considers responses to balance perturbations in muscles around the ankle, peroneus longus (PL), tibialis anterior (TA) and soleus (SO). It is investigated if their action is related to previously observed balanc...

Walking is one of the preferred exercises among elderly, but could a prolonged walking increase gait variability, a risk factor for a fall in the elderly? Here we determine whether 30 min of treadmill walking increases coefficient of variation of gait in elderly. Because gait responses to exercise depend on fitness level, we included 15 sedentary a...

Online gait corrections are frequently used to restore gait stability and prevent falling. They require shorter response times than voluntary movements which suggests that subcortical pathways contribute to the execution of online gait corrections. To evaluate the potential role of the cerebellum in these pathways we tested the hypotheses that onli...

Online movement adjustments are crucial for daily life. This is especially true for leg movements in relation to gait, where failed adjustments can lead to falls, especially in elderly. However, most research has focused on reach adjustments following changes in target location. This arm research reports two categories of online adjustments (see Ga...

Background: In negotiating stairs, low foot clearance increases the risk of tripping and a fall. Foot clearance may be related to physical fitness, which differs between active and sedentary participants, and be acutely affected by exercise. Impaired stair negotiation could be an acute response to exercise. Here we determined acute changes in foot...

Background: We aimed to study the contribution of upper limb movements to propulsion during walking in typically developing (TD) children (n = 5) and children with hemiplegic and diplegic cerebral palsy (CP; n = 5 and n = 4, respectively). Methods: Using integrated three-dimensional motion capture data and a scaled generic musculoskeletal model tha...

Traumatic brain injury (TBI) often leads to impairments in gait performance. However, the underlying neurostructural pathology of these gait deficits is poorly understood. We aimed to investigate regional gray matter (GM) volume in young moderate-to-severe TBI participants (n = 19; age 13 years 11 months ±3 years 1 month), compared with typically d...

Little is known about the ability of blind people to cross obstacles after they have explored haptically their size and position. Long-term absence of vision may affect spatial cognition in the blind while their extensive experience with the use of haptic information for guidance may lead to compensation strategies. Seven blind and 7 sighted partic...

In this observational case-control study we aimed to determine whether altered arm postures in children with unilateral CP (uniCP) are related to gait instability in a specific direction. Antero-posterior and medio-lateral Foot Placement Estimator instability measures and arm posture measures (vertical and antero-posterior hand position, sagittal a...

Background. Even though lower-limb motor disorders are core features of spastic cerebral palsy (sCP), the relationship with brain lesions remains unclear. Unraveling the relation between gait pathology, lower-limb function, and brain lesions in sCP is complex for several reasons; wide heterogeneity in brain lesions, ongoing brain maturation, and ga...

Locomotor malfunction represents a major problem in some neurological disorders like stroke and spinal cord injury. Robot-assisted walking devices have been used during rehabilitation of patients with these ailments for regaining and improving walking ability. Previous studies showed the advantage of brain-computer interface (BCI) based robot-assis...

Gait cycles were determined according to the right heel strike (red dots) using the accelerometer’s data from the right (blue continue line) leg. The left leg’s accelerometer data is as well illustrated (black dotted line) for comparisons. (TIF)

Power density analysis of EMG artifacts in healthy volunteers. a. Spectral density analysis over all electrodes for active and passive walking and the baseline before passive and active walking conditions. b. Topographic distribution of event related desynchronization (ERD) and synchronization (ERS) in the mu (8–12 Hz), beta (15-30Hz) and low gamma...

Supporting Information. (PDF)

Studies on neural decision making mostly investigated fast corrective adjustments of arm movements. However, fast leg movement corrections deserve attention as well, since they are often required to avoid falling after balance perturbations. The present study aimed at elucidating the mechanisms behind fast corrections of tripping responses by analy...

Complex gait (e.g. obstacle avoidance) requires a higher cognitive load than simple steady state gait, which is a more automated movement. The higher levels of the central nervous system, responsible for adjusting motor plans to complex gait, develop throughout childhood into adulthood. Therefore, we hypothesize that gait strategies in complex gait...

Many patients with traumatic brain injury (TBI) suffer from postural control impairments that can profoundly affect daily life. The cerebellum and brain stem are crucial for the neural control of posture and have been shown to be vulnerable to primary and secondary structural consequences of TBI. The aim of this study was to investigate whether mor...

Making step adjustments is an essential component of walking. However, the ability to make step adjustments may be compromised when the walker’s attentional capacity is limited. This study compared the effects of ageing and dual tasking on step adjustments in response to stepping target perturbations during visually cued treadmill walking. Fifteen...

To prevent falls, adjustment of foot placement is a frequently used strategy to regulate and restore gait stability. While foot trajectory adjustments have been studied during discrete stepping, online corrections during walking are more common in daily life. Here, we studied quick foot placement adjustments during gait, using an instrumented tread...

There are several control mechanisms that contribute to keep gait stability under the presence of perturbations. For larger perturbations, responses with longer latencies produce adequate reactions to the perturbation. Latencies might be shorter, and the risk for falling might decrease provided that the reaction is adequate. It is possible that tra...

To walk efficiently and stably on different surfaces under various constrained conditions, humans need to adapt their gait pattern substantially. Although the mechanisms behind locomotor adaptation are still not fully understood, the cerebellum is thought to play an important role. Here we aimed to address the specific localization of cerebellar in...

Gait adaptation is essential for humans to walk according to the different demands of the environment. Although locomotor adaptation has been studied in different contexts and in various patient populations, the mechanisms behind locomotor adaptation are still not fully understood. The aim of the present study was to test two opposing hypotheses ab...

Background and aim: The ability to modify attentional resources to variations in terrain complexity is of critical importance for safe community ambulation. Age-related changes in cognitive and visual control of walking may influence this ability among elderly people. As executive function (EF) affects the ability to efficiently deal with changes i...

Maturation of level walking reaches adult-like behavior around the age of 5 years [1,2]. However, studies on more complex walking situations (e.g. obstacle avoidance) suggested ongoing development of anticipatory gait strategies until early adolescence [3-6]. The age at which anticipatory gait strategies are matured is not clearly defined yet becau...

Traumatic brain injury (TBI) can lead to deficits in gait and posture which are often asymmetric. A possible factor mediating these deficits may be asymmetry in strength of the leg muscles. However, muscle strength in the lower extremities has rarely been investigated in (young) TBI patients. Here, we investigated associations between lower extremi...

This chapter discusses the importance of basic and clinical science for the rehabilitation of patients with stroke or SCI (spinal cord injury). Examples are given from novel approaches in rehabilitation. Insights can be obtained by investigating normal locomotor or postural activity but it is argued that the use of more challenging locomotor tasks...

We investigated whether balance control in young TBI patients can be promoted by an 8-week balance training program and whether this is associated with neuroplastic alterations in brain structure. The cerebellum and cerebellar peduncles were selected as regions of interest because of their importance in postural control as well as their vulnerabili...

The aim of this study was to examine how feedback, or its absence, affects children with Developmental Coordination Disorder (DCD) during a visuo-manual tracking task. This cross-sectional study included 40 children with DCD and 40 typically developing (TD) children between six and ten years old. Participants were required to track a target moving...

Modulation of cutaneous reflexes is important in the neural control of walking, yet knowledge about underlying neural pathways is still incomplete. Recent studies have suggested that the cerebellum is involved. Here, we evaluated the possible roles of the cerebellum in cutaneous reflex modulation and in attenuation of self-induced reflexes. First i...

In a recent work on locomotor symmetry while walking on a split-belt treadmill, Lauzière and co-workers determined the perception threshold of gait symmetry in a sample of healthy elderly. In addition, they aimed to determine which particular gait parameters affect the symmetry of the perception threshold. Although only temporal and kinetic gait pa...

Finding muscle activity generating a given motion is a redundant problem, since there are many more muscles than degrees of freedom. The control strategies determining muscle recruitment from a redundant set are still poorly understood. One theory of motor control suggests that motion is produced through activating a small number of muscle synergie...

Study design: Case series. Objectives: To determine the optimal testing speed at which the recovery of the EMG (electromyographic) activity should be assessed during and after body weight supported (BWS) locomotor training. Setting: Tertiary hospital, Sint Maartenskliniek, Nijmegen, The Netherlands. Methods: Four participants with incomplete...

Tripping over obstacles is one of the main causes of falls. One potential hazard to actually fall when tripped is inadequate foot landing. Adequate landing is required to control the body's angular momentum, while avoiding dangerous surfaces (slippery patch, uneven ground). To avoid such dangers, foot trajectory needs to be controlled by inhibiting...

Understanding age-related decline in gait stability and the role of alterations in brain structure is crucial. Here, we studied the relationship between white matter microstructural organization using Diffusion Tensor Imaging (DTI) and advanced gait stability measures in 15 healthy young adults (range 18-30 years) and 25 healthy older adults (range...

During walking, attention needs to be flexibly allocated to deal with varying environmental constraints. This ability may be affected by aging and lower overall executive function. The present study examined the influence of aging and executive function on the attentional costs of visually guided walking under different task demands. Three groups,...

Background Spasticity is an important complication after stroke, especially in the anti-gravity muscles, i.e. lower limb extensors. However the contribution of hyperexcitable muscle spindle reflex loops to gait impairments after stroke is often disputed. In this study a neuro-musculoskeletal model was developed to investigate the contribution of an...

Freezing of gait is an episodic gait disorder, characterized by the inability to generate effective forward stepping movements. The pathophysiology underlying freezing of gait remains insufficiently understood, and this hampers the development of better treatment strategies. Preliminary evidence suggests that impaired force control during walking m...

There is growing evidence that human locomotion is controlled by flexibly combining a set of basic muscle activity patterns. To explore how these patterns are modified to cope with environmental constraints, ten healthy young adults first walked on a split-belt treadmill at symmetric speeds of 4 and 6 km/h for 2 min. An asymmetric condition was the...

Based on the windlass mechanism theory of Hicks, the medial longitudinal arch (MLA) flattens during weight bearing. Simultaneously, foot lengthening is expected. However, changes in foot length during gait and the influence of walking speed has not been investigated yet. The foot length and MLA angle of 34 healthy subjects (18 males, 16 females) at...

Lateral stability during gait is of utmost importance to maintain balance. This was studied on human subjects walking on a treadmill who were given 100-ms perturbations of known magnitude and timing with respect to the gait cycle by means of a computer-controlled pneumatic device. This method has the advantage that the same perturbations can be giv...

Fast cyclic movements and discrete motor acts are controlled differently, presumably because fast cyclic tasks are more automated, thereby depending on different circuits. If fast cyclic movements are made less predictable (e.g., by mixing frequencies), one would predict that their control will be less automated, requiring increased activity in mot...

Objective: Limb kinematics in backward walking (BW) are essentially those of forward walking (FW) in reverse. It has been argued that subcortical mechanisms could underlie both walking modes. Methods: Therefore, we tested whether participants with supraspinal/cortical deficits (i.e. cerebral palsy) show the kinematic reversal from FW to BW. 3D gait...

Dual-task designs have been used widely to study the degree of automatic and controlled processing involved in postural stability of young and older adults. However, several unexplained discrepancies in the results weaken this literature. To resolve this problem, a careful selection of dual-task studies that met certain methodological criteria are...

Maintaining mediolateral (ML) balance is very important to prevent falling during walking, especially at very slow speeds. The effect of walking speed on support and propulsion of the center of mass (COM) has been focus of previous studies. However, the influence of speed on ML COM control and the associated coupling with sagittal plane control rem...

Facilitation of leg muscle activity by active arm movements during locomotor tasks could be beneficial during gait rehabilitation after spinal cord injury. The present study explored the effects of arm movements on leg muscle activity during sub-maximal recumbent stepping. Healthy subjects exercised on a recumbent stepping machine both with and wit...

Previous studies comparing forward (FW) and backward (BW) walking suggested that the leg kinematics in BW were essentially those of FW in reverse. This led to the proposition that in adults the neural control of FW and BW originates from the same basic neural circuitry. One aspect that has not received much attention is to what extent development p...