Biomedical subjects

Theo Mulder

Publications and source records attributed to Theo Mulder.

18 recordsLinked to original sources

PubMed2007

Relationship between landing strategy and patellar tendinopathy in volleyball.

OBJECTIVE: The aetiology of patellar tendinopathy (jumper's knee) remains unclear. To see whether landing strategy might be a risk factor for the development of this injury, this study examined whether landing dynamics from drop jumps differed among healthy volleyball players (CON) and volleyball players with a jumper's knee. The patients with jumper's knee were divided into an asymptomatic group with a previous jumper's knee (PJK) and a symptomatic group with a recent jumper's knee (RJK). METHODS: Inverse dynamics analyses were used to estimate lower extremity joint dynamics from 30, 50 and 70 cm drop jumps in the three groups (CON, n = 8; PJK, n = 7; RJK, n = 9). A univariate repeated measures analysis of variance was used to compare the different landing techniques. RESULTS: Data analysis of the landing dynamics revealed that PJK showed higher knee angular velocities (p<0.01), and higher ankle plantar flexion moment loading rate (p<0.01). Furthermore, strong tendencies of higher loading rate of vertical ground reaction force (p = 0.05) and higher knee extensor moment loading rate (p = 0.08) were found compared with CON. Higher values for peak knee moment, peak knee power and knee work (all p<0.01) were found for CON compared with RJK. The comparison of the two jumper's knee groups yielded higher knee angular velocities (p<0.01), together with higher ankle plantar flexion and knee extensor moment loading rate (p<0.01 and p<0.05, respectively). CONCLUSION: Where RJK used a landing technique to avoid high patellar tendon loading, PJK used a stiffer landing strategy, which may be a risk factor in the development of patellar tendinopathy.

Adult↗

PubMed2007

Motor imagery and stroke rehabilitation: a critical discussion.

Motor disorders are a frequent consequence of stroke and much effort is invested in the re-acquisition of motor control. Although patients often regain some of their lost function after therapy, most remain chronically disabled. Functional recovery is achieved largely through reorganization processes in the damaged brain. Neural reorganization depends on the information provided by sensorimotor efferent-afferent feedback loops. It has, however, been shown that the motor system can also be activated "offline" by imagining (motor imagery) or observing movements. The discovery of mirror neurones, which fire not only when an action is executed, but also when one observes another person performing the same action, also show that our action system can be used "online" as well as offline. It is an intriguing question as to whether the information provided by motor imagery or motor observation can lead to functional recovery and plastic changes in patients after stroke. This article reviews the evidence for motor imagery or observation as novel methods in stroke rehabilitation.

Cognition↗

PubMed2006

Walking trajectory in neglect patients.

A lateral deviation of the walking trajectory is often observed in stroke patients with unilateral spatial neglect. However, existing research appears to be contradictory regarding the direction of this deviation. The aim of the present study was to gain more insight into the walking trajectory of neglect patients. Twelve right hemisphere stroke patients (six neglect, six no neglect), eight left hemisphere stroke patients (none neglect) and 10 healthy control subjects were instructed to walk towards a target while a two-dimensional ultrasonic positioning system recorded their walking trajectory. Patients' recovery of walking ability was assessed and they were tested for the presence of neglect. Neglect patients showed a larger lateral deviation in their walking trajectory compared to stroke patients without neglect or controls. Neglect patients with good walking ability showed a deviation to the contralesional side. Neglect patients with limited walking ability showed a deviation to the ipsilesional side. Within the neglect group we found no relation between the severity of neglect and lateral deviation. Differences in walking ability may account for the contradictory results between studies regarding the lateral deviation in neglect patients' walking trajectory. We suggest that when a neglect patient's walking ability is limited, walking towards a target becomes a dual task: heading control and walking. A limited walking ability will cause a higher task priority of walking compared to heading control. This shift in task priority may be causing the change in walking trajectory deviation.

Adult↗

PubMed2006

A five-week exercise program can reduce falls and improve obstacle avoidance in the elderly.

BACKGROUND: Falls in the elderly are a major health problem. Although exercise programs have been shown to reduce the risk of falls, the optimal exercise components, as well as the working mechanisms that underlie the effectiveness of these programs, have not yet been established. OBJECTIVE: To test whether the Nijmegen Falls Prevention Program was effective in reducing falls and improving standing balance, balance confidence, and obstacle avoidance performance in community-dwelling elderly people. METHODS: A total of 113 elderly with a history of falls participated in this study (exercise group, n = 79; control group, n = 28; dropouts before randomization, n = 6). Exercise sessions were held twice weekly for 5 weeks. Pre- and post-intervention fall monitoring and quantitative motor control assessments were performed. The outcome measures were the number of falls, standing balance and obstacle avoidance performance, and balance confidence scores. RESULTS: The number of falls in the exercise group decreased by 46% (incidence rate ratio (IRR) 0.54, 95% confidence interval (CI) 0.36-0.79) compared to the number of falls during the baseline period and by 46% (IRR 0.54, 95% CI 0.34-0.86) compared to the control group. Obstacle avoidance success rates improved significantly more in the exercise group (on average 12%) compared to the control group (on average 6%). Quiet stance and weight-shifting measures did not show significant effects of exercise. The exercise group also had a 6% increase of balance confidence scores. CONCLUSION: The Nijmegen Falls Prevention Program was effective in reducing the incidence of falls in otherwise healthy elderly. There was no evidence of improved control of posture as a mechanism underlying this result. In contrast, an obstacle avoidance task indicated that subjects improved their performance. Laboratory obstacle avoidance tests may therefore be better instruments to evaluate future fall prevention studies than posturographic balance assessments.

Accidental Falls↗

PubMed2006

Psychomotor speed: possibly a new marker for overtraining syndrome.

Overtraining syndrome (OTS) is a major threat for performance and health in athletes. OTS is caused by high levels of (sport-specific) stress in combination with too little regeneration, which causes performance decrements, fatigue and possibly other symptoms. Although there is general consensus about the causes and consequences, many different terminologies have been used interchangeably. The consequences of overreaching and overtraining are divided into three categories: (i) functional overreaching (FO); (ii) non-functional overreaching (NFO); and (iii) OTS. In FO, performance decrements and fatigue are reversed within a pre-planned recovery period. FO has no negative consequences for the athlete in the long term; it might even have positive consequences. When performance does not improve and feelings of fatigue do not disappear after the recovery period, overreaching has not been functional and is thus called NFO. OTS only applies to the most severe cases. NFO and OTS could be prevented using early markers, which should be objective, not manipulable, applicable in training practice, not too demanding, affordable and should be based on a sound theoretical framework. No such markers exist up to today. It is proposed that psychomotor speed might be such a marker. OTS shows similarities with chronic fatigue syndrome and with major depression (MD). Through two meta-analyses, it is shown that psychomotor slowness is consistently present in both syndromes. This leads to the hypothesis that psychomotor speed is also reduced in athletes with OTS. Parallels between commonly used models for NFO and OTS and a threshold theory support the idea that psychomotor speed is impaired in athletes with NFO or OTS and could also be used as an early marker to prevent NFO and/or OTS.

Biomarkers↗

PubMed2005

Six-month effects of the Groningen active living model (GALM) on physical activity, health and fitness outcomes in sedentary and underactive older adults aged 55-65.

OBJECTIVE: To determine the effects on energy expenditure, health and fitness outcomes in sedentary older adults aged 55-65 after 6-month participation in the GALM program. METHODS: In three Dutch communities, subjects from matched neighbourhoods were assigned to an intervention (n = 79) or a waiting-list control group (n = 102). The GALM program consisted of fifteen 60 min sessions once a week emphasising moderate-intensity recreational sports activities. RESULTS: The intervention group showed significant increases in energy expenditure for recreational sports activities, other leisure-time physical activity, health indicators, and perceived and performance-based fitness. Contrary to our expectations, the same increases were found for the control group. Consequently, only significant between-group differences, favouring the intervention group, were obtained for sleep, diastolic blood pressure, perceived fitness score and grip strength. CONCLUSION: The increases in energy expenditure for physical activity from the GALM program, especially for the more intensive recreational sports activities, look promising and are in line with the expected amounts necessary to improve health. Further research is needed to evaluate long-term effects of participation in the GALM program. PRACTICE IMPLICATIONS: These results underline that GALM can be considered successful in stimulating leisure-time physical activity and improving health and fitness in older adults.

Age Factors↗

PubMed2005

Observation, imagination and execution of an effortful movement: more evidence for a central explanation of motor imagery.

In this study subjects had to imagine, observe and perform a series of 25 squat movements while lifting two dumbbells of 12.5 kg each (one with each hand). This movement is effortful and requires substantial activation of peripheral systems. It was asked whether subjects when they imagined that they were performing the movements or when they observed a model performing the squat movements would show increased activity in EMG, heart rate and respiration compared with a control condition where they sat relaxed in a comfortable chair or a condition where they actually performed the squat movements. Two groups of subjects participated in the experiment: experienced squatters and novices. By employing these two groups we were able to study the differential effect of earlier experience with the target movement on peripheral activation. The results showed that with the exception of respiration no significant peripheral activation could be measured related to motor imagery. Although a clear distinction in experience existed between the experienced squatters versus the novices, no relevant imagery-related differences could be obtained between the two groups. The results are discussed in the light of a central explanation of motor imagery.

Adolescent↗

PubMed2005

Differences between participants and non-participants in an RCT on physical activity and psychological interventions for older persons.

BACKGROUND AND AIMS: Volunteer bias in intervention studies on successful aging has been poorly explored. This paper investigated differences between participants and non-participants of the Groningen Intervention Study on Successful Aging (GISSA) over a wide range of demographic, physical, psychological and social subject characteristics. METHODS: Subjects were recruited among a longitudinal cohort study (Groningen Longitudinal Aging Study) and included 558 men and 711 women, aged 65-96 years, who were invited to participate in the GISSA. Measures were obtained by questionnaires at the moment of invitation and eight years before invitation. Participants were compared with three groups of non-participants: persons who refused to participate, those who did not respond after a reminder, and those who intended to participate but withdrew before pre-test. RESULTS: At the moment of invitation, participants were younger, better educated, and functionally and physically more active than the three groups of non-participants. They also had better scores on the physical functioning subscale of the medical outcome scale, better ADL, iADL and vigorous ADL functions and fewer depressive symptoms, and perceived less social support in everyday and problem situations. Participants reported a less strong rate of decline in physical and psychological functioning in the eight years prior to the invitation than did the other groups. CONCLUSION: Due to volunteer bias, results of intervention studies on successful aging may have limited generalizability.

Activities of Daily Living↗

PubMed2005

Patients' and relatives' reports of disturbances 9 months after stroke: subjective changes in physical functioning, cognition, emotion, and behavior.

OBJECTIVE: To quantify the frequency of physical, cognitive, emotional, and behavioral changes as reported by patients and relatives after a stroke and to determine their degree of agreement. DESIGN: Follow-up study of 172 stroke patients to a mean of 9.8 months poststroke and 143 relatives interviewed separately with a questionnaire. SETTING: Home-based stroke patients. PARTICIPANTS: The 172 patients (107 men, 68 women) were a subset of 229 patients enrolled in a previous study. Their mean age +/- standard deviation was 55.3+/-10.9 years (age range, 18-70 y). Other participants were 143 relatives (mostly spouses; 43 men, 100 women) had a mean age of 52.4+/-12.2 years. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURE: Structured interview using a questionnaire. RESULTS: The overall percentage of frequency of different disturbances was comparable between patients' and relatives' reports. However, the degree of agreement between patients and their relatives tended to be low. Several possible explanations for this finding are considered, including the potential role of residuals of anosognosia in this stroke population. CONCLUSIONS: Educating families and rehabilitation specialists about the frequency of disturbances and possible reasons for different opinions between patients and families may provide useful information for therapeutic interventions.

Adolescent↗

PubMed2005

Effect of ageing on the ability to adapt to a visual distortion during walking.

Degradation of major sensory systems such as proprioception, the vestibular system and vision may be a factor that contributes to the decline in walking stability in older people. In the present study this was examined by introducing a visual distortion by means of prism glasses shifting subject's view 10 degrees to the right while subjects walked towards a target (exposure condition). Shifting the view while walking towards a target will cause subjects to alter their heading in such a way that their walking trajectory describes a curvilinear path. It was expected that older people, when compared to young people, would have greater difficulty adjusting their heading and would show a greater decrease in heading stability, quantified by means of the standard deviation of the lateral position (SDLP). This was indeed the case. When performance in a pre- and post-exposure condition, in which subjects walked without prism glasses, were compared to each other, older people (O group) showed a greater decrease in heading stability than young people (Y group) and middle aged people (M group). Furthermore, it appeared that during the exposure condition adaptation effects were present in the Y and M group, which were absent in the O group. It is discussed that this adaptation is a form of realignment of the proprioceptive and visual system. The absence of realignment in the O group is argued to be caused by degradation of the proprioceptive system, which results in a lowering of the proprioceptive bias of vision.

Adaptation, Physiological↗

PubMed2005

Deficits in motor control processes involved in production of graphic movements of children with attention-deficit-hyperactivity disorder.

This study aimed to investigate whether two distinct motor control processes, i.e. motor planning and parameter setting, were impaired in children with attention-deficit-hyperactivity disorder (ADHD). An experiment was designed in which children copied figures of increasing complexity under increasing accuracy levels on a digitizer. Sixteen children with ADHD (11 males, 5 females; mean age 8 y 4 mo, SD 1 y 1 mo) and 16 comparison children, without impairment, matched for age and sex participated. ADHD was diagnosed by a psychiatrist following the criteria of the DSM-V. Only children with IQ scores greater than 80 were included. Across all graphic tasks, children with ADHD made slower, inaccurate strokes with relatively high axial pen force compared with the comparison group. No evidence was found for a deficit in motor planning, but parameter setting appeared to be deficient as the ADHD group made less accurate strokes when accuracy demands increased.

Adolescent↗

PubMed2004

Functional recovery of gait and joint kinematics after right hemispheric stroke.

OBJECTIVE: To gain insight into the relation between changes in gait patterns over time and functional recovery of walking ability in stroke patients. DESIGN: Cohort study. SETTING: Inpatient rehabilitation center of a university hospital in the Netherlands. PARTICIPANTS: Thirteen stroke patients admitted, or awaiting admission, for inpatient rehabilitation 3 weeks poststroke, and 16 healthy control subjects. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: At 3, 6, 12, 24, and 48 weeks poststroke, functional recovery of walking ability was assessed with the Rivermead Mobility Index (RMI) and the Functional Ambulation Categories (FAC). When possible, kinematics of the knee, hip, and pelvis were assessed through gait analysis in an 8 x 4 m gait laboratory. Minimal scores of 8 on the RMI and 4 on the FAC were necessary before patients were classified as functionally recovered. RESULTS: Patients whose joint kinematics during ambulation had recovered to within the range of the control group showed functional recovery of walking ability. However, some patients whose kinematics had developed toward an abnormal pattern also showed functional recovery. CONCLUSIONS: Recovery of joint kinematics toward a normal pattern is not required for functional recovery of walking ability. Early recognition of compensatory walking patterns that facilitate functional recovery may have implications for rehabilitation programs.

Adult↗

PubMed2003

The role of motor imagery in learning a totally novel movement.

The aim of the present study is to gain more insight into the mechanisms underlying mental practice. The question of whether a totally novel movement may be learned by mental practice was investigated. Healthy young adults had to learn the abduction of the big toe (dominant right foot) without moving the other toes or the foot. The subjects were divided into two groups: subjects who were absolutely unable to abduct their big toe ("absolute zero" group) and subjects who were able to abduct their toe to some extent but showed clear room for improvement ("already doing it" group). Two separate experiments were executed. In the first experiment, 37 absolute-zero subjects had to practice, mentally or physically, the target movement. In the second experiment 40 already-doing-it subjects had to improve their toe-abduction skill. The results showed that absolute-zero subjects could not acquire the toe-abduction movement by means of mental practice. Only subjects who physically practiced the target movement improved significantly. Subjects who had some experience in the task (already-doing-it subjects) improved significantly after mental practice as well as after physical practice. The results seem to indicate that it is more plausible to explain the learning effects of mental practice in terms of a "top-down" mechanism based on the activation of a central representation of the movement than in terms of a peripheral "bottom-up" mechanism based on the activation of muscles.

Adult↗

PubMed2003

Pharmacologic treatment of complex regional pain syndrome I: a conceptual framework.

Pain may be a leading symptom in complex regional pain syndrome type I (CRPS I) and may hinder functional recovery. In this case, a pharmacotherapeutic approach to pain should be part of the individually tailored interdisciplinary treatment regimen. However, operational criteria for determining which patient may profit from what therapeutic intervention are lacking. This article discusses a conceptual framework in which the rapid progress made in basic pain research may contribute to the clinical management of pain in CRPS I. First, recent insights in the pathophysiologic mechanisms underlying CRPS I are reviewed. CRPS I is considered a neuropathic pain syndrome with a mixed and time-dependent profile of a regional inflammation, sensitization of primary somatosensory afferents (peripheral sensitization), and sensitization of spinal neurons (central sensitization). The dominant mechanisms may vary across individual patients with different time profiles. Second, a model was constructed in which signs and symptoms in an individual patient are related to these mechanisms. Finally, relating the clinical picture to the underlying pathophysiology may help determine the pharmacotherapeutic approach for an individual patient. Pharmacologic options are discussed in this context. The presented framework does not aim to provide an evidence-based treatment algorithm, ready to be used in daily clinical practice; rather it offers a crude, first step toward a mechanism-based pharmacotherapy in CRPS I, in an effort to shift from a mainly empirical treatment paradigm toward theory-driven treatment procedures.

Animals↗

PubMed2003

Reorganization of gait after limb-saving surgery of the lower limb.

OBJECTIVE: In this study, the concept of a cognitive dual-task performance and visual restriction during walking has been used to study the recovery of gait after limb-saving surgery in ten patients. DESIGN: All patients were recovering from some form of treatment to tumors of the lower limbs. Patients had to walk on a treadmill at their preferred speed. During the course of recovery, we measured normal walking, walking while performing an attention-demanding dual task, and walking during restricted vision, starting 5 mo postoperatively. RESULTS: Patients are able to reach an acceptable level of gait within 15 mo, especially when the basic locomotor activity (i.e., step-cycle duration, walking speed, gait symmetry) is taken into account. Nevertheless, the results showed that during the recovery, the patients were still hindered by the dual task and visual restriction while walking because they exhibited a decrease in step-cycle duration under these conditions. CONCLUSIONS: In general, an improvement in walking speed and a decrease in asymmetry was seen. On the other hand, patients still had a basically reduced control of gait after the 15-mo recovery period. This can be attributed to a lack of gait automatism caused by an irreversible loss of somatosensory input.

Adult↗

PubMed2002

Assessment of motor recovery and decline.

Assessment of motor disorders forms an important ingredient of neurology, rehabilitation medicine and orthopaedics. Until now, however, many of the employed assessment tools are derived from empirical knowledge. Almost no relation exists with modern theoretical notions about motor control. In the present article, motor control theory is reviewed in the light of its potential contribution to understanding motor recovery. An attempt is made to present a theoretical framework for the assessment of motor disorders related to recent insights in motor control. The framework emphasizes the dynamical character of recovery. The principle of output optimization is discussed and it is stressed that compensation plays a permanent role in adapting to damage of the body or to changes in the environment. An assessment procedure is introduced to measure the (mental) costs of this compensation. It is argued that changes in the costs of compensation across time reflect recovery.

Adaptation, Physiological↗

PubMed2002

Reflex sympathetic dystrophy of the left hand and motor impairments of the unaffected right hand: impaired central motor processing?

OBJECTIVE: To test whether central motor processing can be impaired in chronic reflex sympathetic dystrophy (RSD). DESIGN: Experimental 2-group analysis. SETTING: Tertiary care center in the Netherlands. PARTICIPANTS: Five patients with stage 3 RSD of the left forearm, free of symptoms and complaints in the right forearm; and 10 healthy control subjects. INTERVENTION: On a digitizer, RSD patients and controls had to draw 3 sequences of graphemes of different complexity with their (unaffected) dominant right hand. The drawing tracks were segmented in time periods between points of velocity minima of the pen tip. MAIN OUTCOME MEASURES: Mean velocity, coefficients of variation of both length and movement time per segment, and mean intersegmental pausing time were calculated for each sequence. RESULTS: A repeated-measures analysis of variance by using the multivariate method yielded a 35% lower mean velocity (F(1,13) = 5.83, P =.031), a 110% larger segment length variability (F(1,13) = 9.72, P =.008) and a 60% larger variability of movement time per segment (F(1,13) = 5.78, P =.032) in RSD patients. No group difference was found for intersegmental pausing time or any interaction effect with the type of task. CONCLUSION: Patients with chronic RSD have a normal ability to preprogram sequential movements of their unaffected hand; but with impaired temporospatial coding and movement execution. We concluded that cortical mechanisms may be involved in motor impairments in patients with chronic RSD.

Adult↗

PubMed2002

Motor control impairment of the contralateral wrist in patients with unilateral chronic wrist pain.

OBJECTIVE: Assessment of the quality of fine motor control in patients with unilateral chronic wrist pain seldom focuses on the possibility that control of movements is effector independent at the cerebral level. This mechanism may be involved in an impairment of motor function in the unaffected wrist. We studied the possible motor impairment in the unaffected wrist in patients with chronic wrist pain. DESIGN: Eighteen patients with chronic wrist pain in their dominant hand and 20 healthy controls performed, using their nondominant hand, back-and-forth, left-to-right stroke patterns with a pen on a digital writing tablet connected to a computer. Fluency of movement, defined as the number of zero-crossings of the acceleration curve (pZC), average stroke size, and average velocity were calculated. RESULTS: The controls moved significantly more fluently than the patients (pZC, 0.26+/-0.07 for controls and 0.46+/-0.20 for patients; P < 0.001), suggesting that long-term afferent disturbances may compromise cerebral motor control mechanisms. CONCLUSIONS: This result is in accordance with the view that chronic pain complaints may be maintained by persistently abnormal cerebral motor control. This finding opens a new perspective on the understanding and treatment of chronic wrist pain.

Adolescent↗