Paul Willems

Paul Willems
Maastricht University | UM · NUTRIM School for Nutrition, Toxicology and Metabolism

About

88
Publications
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Publications

Publications (88)
Article
Full-text available
Evaluating variability and stability using measures for nonlinear dynamics may provide additional insight into the structure of the locomotor system, reflecting the neuromuscular system’s organization of gait. This is in particular of interest when this system is affected by a respiratory disease and it’s extrapulmonary manifestations. This study a...
Article
Full-text available
Background Falls risk is elevated in chronic obstructive pulmonary disease (COPD). However, there is a lack of evidence regarding the contributing factors. Here, we examined the feasibility of, and initial responses to, large walking perturbations in COPD, as well as the adaptation potential of people with COPD to repeated walking perturbations tha...
Article
Full-text available
Understanding balance and gait deficits in vestibulopathy may help improve clinical care and our knowledge of the vestibular contributions to balance. Here, we examined walking speed effects on gait variability in healthy adults and in adults with bilateral vestibulopathy (BVP). Forty-four people with BVP, 12 healthy young adults and 12 healthy old...
Article
Full-text available
In gait stability research, neither self-selected walking speeds, nor the same prescribed walking speed for all participants, guarantee equivalent gait stability among participants. Furthermore, these options may differentially affect the response to different gait perturbations, which is problematic when comparing groups with different capacities....
Preprint
Full-text available
Study of balance and gait deficits associated with vestibulopathy is important for improving clinical care and is critical to our understanding of the vestibular contributions to gait and balance control. Previous studies report a speed-dependency of the vestibular contributions to gait, so we examined the walking speed effects on gait variability...
Article
Full-text available
Background and aim Overground gait assessment is limited by the analysis of multiple strides or both spatiotemporal gait characteristics, while fixed speed treadmill walking restricts natural gait speed variations. The Gait Real-time Analysis Interactive Lab (GRAIL)-based 6-minute walk test (6MWT) enables 3D motion analysis and self-paced treadmill...
Data
Heterogeneity in COPD and healthy elderly group. (PDF)
Data
Boxplots of spatiotemporal gait characteristics in the total sample. (PDF)
Data
Data correction and event detection. (PDF)
Data
Boxplots of spatiotemporal gait characteristics in the sub-analysis. (PDF)
Article
Full-text available
Background: We investigated whether substituting sitting with standing and self-perceived light walking in free-living conditions would improve cardiometabolic risk factors, mood, and cognition in overweight/obese adults. Methods: In a randomized, cross-over study, 24 (m/f: 13/11) sedentary overweight/obese participants (64 ± 7 years, BMI 29 ± 2 kg...
Poster
Full-text available
Poster presentation at the 2nd International Congress on NeuroRehabilitation and Neural Repair, May 2017, Maastricht, The Netherlands.
Article
Full-text available
Background: The 6-minute walk test (6MWT) in a regular hallway is commonly used to assess functional exercise capacity in patients with chronic obstructive pulmonary disease (COPD). However, treadmill walking might provide additional advantages over overground walking, especially if virtual reality and self-paced treadmill walking are combined. Th...
Article
Introduction: Bilateral vestibular hypofunction causes balance deficits, increases falls risk and decreases quality of life [1]. Recent work has demonstrated that vestibulo-ocular reflexes [2] and postural responses [3] can be elicited by electrical stimulation via vestibular implants. Research question: This pilot study aimed to determine if elec...
Conference Paper
Patients with COPD have an increased fall risk and gait disturbances. As falls usually occur during locomotion, characterizing gait patterns is important. To date, 3D gait analysis during a self-paced treadmill 6-minute walk test (6MWT) has not been conducted, while this method gives more insight into gait disturbances during exercise testing in CO...
Article
Full-text available
Sedentary behavior (sitting/lying at low energy expenditure while awake) is emerging as an important risk factor that may compromise the health-related quality of life (HRQoL) of colorectal cancer (CRC) survivors. We examined associations of sedentary time with HRQoL in CRC survivors, 2–10years post-diagnosis. In a cross-sectional study, stage I–II...
Article
Full-text available
Aims/hypothesis: The study investigated cross-sectional associations of total amount and patterns of sedentary behaviour with glucose metabolism status and the metabolic syndrome. Methods: We included 2,497 participants (mean age 60.0 ± 8.1 years, 52% men) from The Maastricht Study who were asked to wear an activPAL accelerometer 24 h/day for 8...
Article
Full-text available
Purpose Previous research indicates that sedentary behavior is unfavorably associated with health-related quality of life (HRQoL) of colorectal cancer (CRC) survivors. Using isotemporal substitution modeling, we studied how substituting sedentary behavior with standing or physical activity was associated with HRQoL in CRC survivors, 2–10 years post...
Article
Full-text available
As accelerometers are commonly used for 24-h measurements of daily activity, methods for separating waking from sleeping time are necessary for correct estimations of total daily activity levels accumulated during the waking period. Therefore, an algorithm to determine wake and bed times in 24-h accelerometry data was developed and the agreement of...
Article
Background: Calcaneal fractures are associated with substantial morbidity and socioeconomic impact, frequently leading to limited functional outcome and high economic costs. The Oxford foot model (OFM) has been reported as a valid addition to the biomechanical examination of the foot. The aim of our study was to analyze the gait of patients after...
Article
A previous study by Savelberg et al. indicated higher plantar flexion moments at 40% of the stance phase and simultaneously an increase in plantar loading in people with diabetic polyneuropathy. It was hypothesised that muscle weakness in the lower extremity caused by polyneuropathy can affect the ability to generate enough momentum during the firs...
Article
Diabetic polyneuropathy (DPN) is a common co morbidity in diabetic patients. It has been associated with diminished muscle strength, impaired mobility and decreased quality of life (QoL). The purpose of this study was to evaluate the acute and long term effect of a moderate intensive intervention on muscle strength, mobility and QoL in patients wit...
Article
Walking aids, such as rollator or draisine, improve mobility and functional exercise performance in individuals with chronic obstructive pulmonary disease (COPD) during an indoor 6-min walk test. However, this test does not reflect everyday walking, which is the most frequently reported problematic activity of daily life in individuals with COPD. T...
Conference Paper
Full-text available
The availability of equipment for pedal force measurement is growing rapidly. However, not the measured pedal force but only its muscular part represents the effort generated by the athlete. To optimize cycling performance it is necessary to understand how interventions (training methods, pedaling techniques, body configurations, visual feedback of...
Article
Full-text available
A valid non-wear algorithm for activity monitors is crucial to avoid the misclassification of sedentary time as non-wear time, and vice versa. Characteristics of the algorithm, such as time windows, should be well defined and tested. Furthermore, using tri-axial data might influence the algorithm's performance. This study assessed the optimal time...
Article
Full-text available
Background Improving the use (eg, initial visit and revisits) of Internet-delivered interventions to promote healthy lifestyles such as non-smoking is one of the largest challenges in the field of eHealth. Prompts have shown to be effective in stimulating reuse of Internet-delivered interventions among adults and adolescents. However, evidence conc...
Article
Full-text available
Higher plantar pressures play an important role in the development of plantar foot ulceration in diabetic polyneuropathy and earlier studies suggest that higher pressures under the forefoot may be related to a decrease in lower leg muscle strength. Therefore, in this randomised controlled trial we evaluated whether lower-extremity strength training...
Article
The aim of this study was to identify the cascade of effects leading from alterations in force generation around the ankle joint to increased plantar pressures under the forefoot. Gait analysis including plantar pressure measurement was performed at an individually preferred and a standardized, imposed gait velocity in diabetic subjects with polyne...
Article
Full-text available
To date, detailed analyses of walking patterns using accelerometers during the 6-min walk test (6MWT) have not been performed in patients with chronic obstructive pulmonary disease (COPD). Therefore, it remains unclear whether and to what extent COPD patients have an altered walking pattern during the 6MWT compared to healthy elderly subjects. 79 C...
Data
Intra-individual differences between best and worst 6-min walk tests. (DOCX)
Data
Patients' characteristics for all COPD patients and a subgroup of COPD patients with a 2nd test. (DOCX)
Article
Full-text available
The purpose of the present study was to distinguish the effects of both diabetes mellitus type 2 (DM2) and diabetic polyneuropathy (DPN) on mobility, muscle strength and health related quality of life (HR-QoL). DPN patients (n=98), DM2 patients without DPN (DC) (n=39) and healthy subjects (HC) (n=19) performed isometric and isokinetic lower limb mu...
Article
Type 2 diabetes mellitus (DM2) patients may have decreased muscle strength. This decline can have multiple causes, among them diabetic polyneuropathy (DPN). We sought to determine the effect of nerve deterioration on muscle strength in DM2 patients with and without DPN. Nineteen DM2 patients with DPN (DPN group), 15 DM2 patients without DPN (DC gro...
Article
In plantar pressure measurement, both peak pressure and pressure time integral are used as variables to assess plantar loading. However, pressure time integral shows a high concordance with peak pressure. Many researchers and clinicians use Novel software (Novel GmbH Inc., Munich, Germany) that calculates this variable as the summation of the produ...
Article
Joint moments have been acknowledged as key factors in understanding gait abnormalities. Gait velocity is further known to affect joint moments and foot pressures. Keeping gait velocity constant is thus a strategy to cancel out the influence of different preferred gait speed between groups. But even if gait velocity is controlled, individuals can c...
Article
People with diabetes or diabetic polyneuropathy often experience limitations in mobility and gait. These limitations are believed to be related to disturbed muscle function and sensory information. In previous studies on diabetic gait, results were confounded by a lower, preferred walking speed in people with diabetes or diabetic polyneuropathy. Th...
Article
Adapted strategies in rising from a chair occur with muscle weakness. To assess whether muscle weakness caused the strategy change, an experimental simulation was performed that allowed to investigate separately effects of reduced muscle capacity and of strategy change on movement dynamics. It was hypothesized that a sit-to-stand (STS) strategy cha...
Article
Full-text available
Patients with diabetic polyneuropathy (DPN) are often confronted with ulceration of foot soles. Increased plantar pressure under the forefoot has been identified as a major risk factor for ulceration. This study sets out to test the hypothesis that changes in gait characteristics induced by DPN related muscle weakness are the origin of the elevated...
Article
Full-text available
This article examined the contribution of selection and influence processes in smoking behavior similarity among friends, and changes in these processes during early and mid adolescence. Data from 1886 Dutch high school students in the control group of the European Smoking prevention Framework Approach (ESFA) study were used. Changes in selection a...
Article
The aim of this study was to study attentional bias when viewing one's own and a control body, and to relate this bias to body-weight and attractiveness ratings. Participants were 51 normal-weight female students with an unrestrained eating style. They were successively shown pictures of their own and a control body for 30s each, while their eye mo...
Chapter
Mensen met diabetes en diabetische polyneuropathie lijken een ander looppatroon te hebben en hebben vaak ook minder spierkracht dan hun gezonde leeftijdsgenoten. Hierdoor lopen ze niet alleen langzamer, maar ook anders: de momenten en krachten rond heup-, knie- en enkelgewricht veranderen en dit heeft gevolgen voor de voetdrukken. Deze theoretische...
Article
The goal of this study was to examine social selection and social influence within reciprocal and non-reciprocal friendships, and the role of parents and siblings, as factors explaining similarity of smoking behaviour among adolescent friends. A new social selection-social influence model is proposed. Longitudinal design with two measurements. Data...
Article
In this study the effect of a changed load/capacity ratio on sit-to-stand performance and on the underlying net joint moments was investigated. In subjects with muscle weakness the load/capacity ratio is increased due to reduced muscle capacity. In the current study this ratio was manipulated by changing the load. This approach allowed studying the...
Article
Previous studies showed age-related redistribution of joint torques from ankle joint plantar flexion to hip joint extension in gait. In the present study it was hypothesized that running can prevent the occurrence of this joint torque redistribution. Four groups of subjects participated in this study (young and elderly both physically active and in...
Chapter
The aim of this study was to compare the human-surface interaction during running on artificial soccer turf pitches. For this purpose a biomechanical analysis (kinetics and kinematies) was performed on twenty soccer players while they ran at three different speeds across a 25 meter long track covered with a third generation artificial soccer turf....
Article
Numerical models of contracting muscle offer a powerful tool to study local mechanical load. For validation of these models, the spatial and temporal distribution of strain was quantified in fixed-end contracting rat tibialis anterior muscle in situ at optimal muscle length (L(o)) and at 120 degrees plantar flexion as well as at 125 and 33Hz stimul...
Article
In this study, the deformation of different fibers of the rat m. plantaris during "isometric" contractions at different muscle lengths was considered. Because the m. plantaris has an obviously inhomogeneous architecture, its fibers on the medial side of the muscle belly are judged to be shorter than those on the lateral side of it. It was expected...
Article
The availability of animal models with disrupted genes has increased the need for small-scale measurement devices. Recently, we developed an experimental device to assess in situ mechanical properties of isometric contractions of intact muscle complexes of the mouse. Although this apparatus provides valuable information on muscle mechanical perform...
Article
An isometric torque sensor for measuring in situ contractions of plantar or dorsal flexors of intact mouse hindlimb has been developed and evaluated. With this device, muscle torque can be accurately measured within the range of -14 mN.m to +14 mN.m. Special attention was paid to fixation of the mouse hindlimb to the measurement device. Halothane-a...
Article
Full-text available
A series of 8 experiments examined the phenomenon that a rapid aimed hand movement is executed faster when it is performed as a single, isolated movement than when it is followed by a second movement (the 1-target advantage). Three new accounts of this effect are proposed and tested: the eye movement hypothesis, the target uncertainty hypothesis, a...
Article
An isometric torque sensor for measuring in situ contractions of plantar or dorsal flexors of intact mouse hindlimb has been developed and evaluated. With this device, muscle torque can be accurately measured within the range of –14 mN·m to +14 mN·m. Special attention was paid to fixation of the mouse hindlimb to the measurement device. Halothane-a...
Article
Full-text available
A series of 8 experiments examined the phenomenon that a rapid aimed hand movement is executed faster when it is performed as a single, isolated movement than when it is followed by a second movement (the 1-target advantage). Three new accounts of this effect are proposed and tested: the eye movement hypothesis, the target uncertainty hypothesis, a...
Article
An important assumption in 2D numerical models of skeletal muscle contraction involves deformation in the third dimension of the included muscle section. The present paper studies the often used plane strain description. Therefore, 3D muscle surface deformation is measured from marker displacements during isometric contractions at various muscle le...
Article
Full-text available
Optical marker tracing methods have been applied successfully in recent years to quantify local material deformation of heart tissue, skin and striated muscles. In this study, polystyrene fluorescent spheres (d = 0.6 mm) are glued to the ventral serosal bladder wall in the rabbit. Three dimensional video registration of the polystyrene spheres is u...
Article
An in vivo method for measuring local deformations of the surface of skeletal muscles is presented. The method was applied to the aponeurosis of the medial gastrocnemius muscle (MG) of cat. Approximately 150 fluorescent polystyrene markers were attached to the aponeurosis and the distal muscle fibres of the MG. Two-dimensional video recordings of t...
Article
Uniaxial confined compression and swelling experiments on cylindrical specimens taken either in an axial or in a radial direction from a canine lumbar annulus fibrosus are presented. The loading protocol consisted of a combination of stepwise mechanical and chemical loading. Swelling and consolidation curves of normalized displacement versus square...
Chapter
A finite deformation model for charged hydrated tissues, such as the intervertebral tissue, is developed. The model predicts not only the response to a mechanical load but also to a chemical load. This response is characterised by ion diffusion, fluid flow relative to the solid matrix and osmotic pressure. The reasonable agreement between experimen...