Biomedical subjects

Hermie J Hermens

Publications and source records attributed to Hermie J Hermens.

At least 19 recordsLinked to original sources

PubMed2006

Behaviour of motor unit action potential rate, estimated from surface EMG, as a measure of muscle activation level.

BACKGROUND: Surface electromyography (EMG) parameters such as root-mean-square value (RMS) are commonly used to assess the muscle activation level that is imposed by the central nervous system (CNS). However, RMS is influenced not only by motor control aspects, but also by peripheral properties of the muscle and recording setup. To assess motor control separately, the number of motor unit action potentials (MUAPs) per second, or MUAP Rate (MR) is a potentially useful measure. MR is the sum of the firing rates of the contributing MUs and as such reflects the two parameters that the CNS uses for motor control: number of MUs and firing rate.MR can be estimated from multi-channel surface EMG recordings. The objective of this study was to explore the behaviour of estimated MR (eMR) in relation to number of active MUs and firing rate. Furthermore, the influence of parameters related to peripheral muscle properties and recording setup (number of fibers per MU, fiber diameter, thickness of the subcutaneous layer, signal-to-noise-ratio) on eMR was compared with their influence on RMS. METHODS: Physiological parameters were varied in a simulation model that generated multi-channel EMG signals. The behaviour of eMR in simulated conditions was compared with its behaviour in experimental conditions. Experimental data was obtained from the upper trapezius muscle during a shoulder elevation task (20-100 N). RESULTS: The simulations showed strong, monotonously increasing relations between eMR and number of active MUs and firing rate (r(2) > 0.95). Because of unrecognized superimpositions of MUAPs, eMR was substantially lower than the actual MUAP Rate (aMR). The percentage of detected MUAPs decreased with aMR, but the relation between eMR and aMR was rather stable in all simulated conditions. In contrast to RMS, eMR was not affected by number of fibers per MU, fiber diameter and thickness of the subcutaneous layer. Experimental data showed a strong relation between eMR and force (individual second order polynomial regression: 0.96 < r(2) < 0.99). CONCLUSION: Although the actual number of MUAPs in the signal cannot be accurately extracted with the present method, the stability of the relation between eMR and aMR and its independence of muscle properties make eMR a suitable parameter to assess the input from the CNS to the muscle at low contraction levels non-invasively.

Journal Article↗

PubMed2006

Myoelectric manifestations of fatigue at low contraction levels in subjects with and without chronic pain.

The aim of the present study was to investigate differences in myoelectric responses to fatigue development between cases with chronic neck-shoulder pain (n=10) and healthy controls (n=10) during a low force level sustained contraction. Subjects performed a 15-min isometric shoulder elevation at a force level of 40 N (sustained contraction), preceded and followed by a step contraction, consisting of five force levels from 20 to 100 N. EMG recordings were made with a two-dimensional electrode array on the upper trapezius of the dominant side. Root-mean-square (RMS(G)), median power frequency (FMED(G)), conduction velocity (CV), number of motor unit action potentials per second (MUAP Rate) and MUAP shape properties were estimated. Changes over time and differences between the groups were statistically evaluated with a linear mixed model. During the sustained contraction, cases showed less increase in RMS(G) than controls (controls: 58.5%, cases: 33.0%). FMED(G) and CV decreased in controls (FMED(G): -6.3%, CV: -5.3%) and stayed constant (FMED(G)) or slightly increased (CV, 3.15%) in cases. Overall, cases showed a less pronounced myoelectric response to the fatiguing task than controls, which may be related to additional recruitment of higher-threshold MUs. A possible explanation might be that cases were already (chronically) fatigued before the experiment started.

Adult↗

PubMed2006

Comparison of electric stimulation methods for reduction of triceps surae spasticity in spinal cord injury.

OBJECTIVES: To compare the effect of 3 methods of electric stimulation to reduce spasticity of the triceps surae in patients with complete spinal cord injury (SCI) and to investigate the carryover effect. DESIGN: Placebo-controlled study with repeated measurements after the interventions. SETTING: Research department affiliated with a rehabilitation hospital in the Netherlands. PARTICIPANTS: Ten patients with a complete SCI were recruited from the outpatient population of the rehabilitation hospital. All subjects had American Spinal Injury Association grade A impairment scores, except for one, who had grade C. The patients had no voluntary triceps surae contractibility. INTERVENTIONS: Forty-five minutes of cyclic electric stimulation of the agonist, antagonist, or dermatome of the triceps surae or a placebo approach. MAIN OUTCOME MEASURES: Outcome measures were the Modified Ashworth Scale (MAS), clonus score, and the H-reflex and M wave (H/M) ratio. The electromyographic response to a stretch of the soleus over the whole range of motion was also determined. The magnitude and ankle angle at which the electromyographic response started were calculated. RESULTS: Stimulation of the agonist provided a significant reduction in the MAS compared with the placebo approach (P<.001). There was no significant change in the H/M ratio or the electromyographic response amplitude after any of the stimulation methods, whereas stimulation of the antagonist muscle resulted in a significant reduction in the ankle angle at which the electromyographic response started, compared with the placebo approach (P<.037). CONCLUSIONS: Triceps surae stimulation reduces the MAS for that specific muscle, whereas the angle at which the reflex starts changes after antagonist stimulation.

Adult↗

PubMed2006

Influence of posture and muscle length on stretch reflex activity in poststroke patients with spasticity.

OBJECTIVE: To investigate the influence of different positions on stretch reflex activity of knee flexors and extensors measured by electromyography in poststroke patients with spasticity and its expression in the Ashworth Scale. DESIGN: Crossover trial with randomized order of positioning. SETTING: Outpatient rehabilitation center in the Netherlands. PARTICIPANTS: Poststroke patients (N = 19) with lower-limb spasticity. INTERVENTION: Changing position: sitting versus supine. MAIN OUTCOME MEASURES: Root mean square (RMS) values of muscle activity and goniometric parameters, obtained during the pendulum test and passive knee flexion and extension, and Ashworth scores. RESULTS: RMS values of bursts of rectus femoris activity were significantly higher in the supine compared with the sitting position (P = .006). The first burst of vastus lateralis activity during the pendulum test (P = .049) and semitendinous activity during passive stretch (P = .017) were both significantly higher in the supine versus the sitting position. For both the pendulum test and passive movement test, the duration and amplitude of the cyclic movement of the lower leg changed significantly as well. In the supine position, we found significantly higher Ashworth scores for the extensors (P = .001) and lower scores for the flexors (P = .002). CONCLUSIONS: The outcome of clinical and neurophysiologic assessment of spasticity is influenced considerably by subject positioning.

Cross-Over Studies↗

PubMed2006

Changes in pain, disability, and muscle activation patterns in chronic whiplash patients after ambulant myofeedback training.

OBJECTIVE: The aim of this exploratory study was to investigate changes in pain, disability, and muscle activation patterns in patients with chronic whiplash-associated disorder (WAD) after 4 weeks of myofeedback training. METHODS: Eleven WAD patients received ambulatory myofeedback training, during which upper trapezius muscle activation and relaxation were continuously recorded and processed for 4 weeks. Feedback was provided when muscle relaxation was insufficient. Pain in neck, shoulders, and upper back (Visual Analogue Scale), disability (Neck Disability Index), and muscle activation patterns during rest, typing, and stress tasks (surface electromyography) were assessed before and after the 4 weeks of training. RESULTS: Pain intensity decreased after 4 weeks of training. Clinically relevant changes were found with regard to pain in the neck and upper back region (55% of the patients), right shoulder (64%), and left shoulder (18%). A trend for decreased disability was found which was clinically relevant in 36% of the patients. A remarkable reduction was found in the Neck Disability Index items concerning headache and lifting weights. Overall, muscle activation was lower and muscle relaxation was higher after the training period with the largest differences during rest. Clinically relevant changes in surface electromyography parameters were found in a minority of patients. CONCLUSION: Four weeks of ambulant training may be beneficial in reducing pain and disability levels and normalizing muscle activation patterns in chronic WAD patients. A randomized-controlled study is recommended to further explore the effects of myofeedback training.

Activities of Daily Living↗

PubMed2006

Effects of age and timing of augmented feedback on learning muscle relaxation while performing a gross motor task.

OBJECTIVE: To examine the combined effect of age and timing of augmented feedback on learning muscle relaxation. Performing a gross motor task, subjects had to lower their trapezius muscle activity using the electromyographic signal as visual myofeedback. DESIGN: Healthy subjects (16 young adults: 20-35 yrs; and 16 older adults: 55-70 yrs) were randomly assigned to one of two timing conditions of myofeedback: concurrent (feedback was provided immediately during the trial) and terminal (feedback was provided delayed after the trial) condition. RESULTS: The results indicated that young adults had a higher level of motor performance (i.e., lower muscle activity) compared with older adults when myofeedback was provided. These effects persisted during short- (after 10 mins) and long-term retention (after 1 wk) when no myofeedback was provided. In contrast to young adults, older adults did not improve their performance throughout the experiment. There were no interactions of age with the timing conditions of myofeedback during acquisition and retention. CONCLUSIONS: Either timing condition of augmented feedback was equally helpful to young adults, whereas neither was helpful for older adults in learning muscle relaxation.

Adult↗

PubMed2006

Tele-treatment of patients with amyotrophic lateral sclerosis (ALS).

Management of patients with amyotrophic lateral sclerosis (ALS) mainly consists of (psycho) social support and advice on activities of daily living. We evaluated the effects of tele-treatment in addition to the conventional method of care in four patients with ALS. A Web application was built with information about ALS and a link to the tele-treatment environment. The latter contained a chat room and a link to start personal computer (PC)-based videoconferencing with a rehabilitation physician. The effect on quality of care was evaluated by questionnaires and interviews. The interviews showed that patients were satisfied with tele-treatment and experienced a pleasant contact during teleconsultations. The rehabilitation physician experienced acceptance of tele-treatment by the patients and a decrease in the time needed for travelling. Tele-treatment was especially suitable for discussing the practical issues about ALS. On the other hand, psychosocial and emotional issues still needed to be discussed during traditional face-to-face contact. Therefore tele-treatment should only be given in addition to face-to-face contact, rather than as a replacement for it.

Adult↗

PubMed2006

Artificial feedback for remotely supervised training of motor skills.

Electromyographic (EMG) biofeedback can be used to train motor functions at a distance, which makes therapy at home a possibility. To enable patients to train properly without the presence of a therapist, artificial feedback is considered essential. We studied the combined effect of age and timing of artificial feedback on training muscle relaxation in 32 healthy subjects (younger: 20-35 years; older: 55-70 years). All subjects improved their performance significantly (F = 6.1, P<0.001). The effect of different timing of feedback (feedback provided during or after performance) was similar in young and older adults. However, this conclusion should be interpreted with caution owing to the small sample size. It can be argued that the artificial feedback used was too complicated for older adults to interpret. When designing remotely supervised treatment programmes, one should consider carefully the way that artificial feedback is being applied as it may enable (elderly) subjects to train without the presence of a therapist.

Aged↗

PubMed2005

Development of a new method for objective assessment of spasticity using full range passive movements.

OBJECTIVE: To develop a method for assessment of spasticity, in which the whole range of motion (ROM) at a wide variation of speeds is applied. DESIGN: Cross-sectional design to study construct validity. SETTING: Research department affiliated with a rehabilitation hospital in The Netherlands. PARTICIPANTS: Nine patients with complete spinal cord injury recruited from the rehabilitation hospital. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Thirty to 45 stretches over the whole ROM were applied to the triceps surae muscle at varying velocities measuring from 30 degrees to 150 degrees/s. Electromyographic responses were measured in order to assess reflex excitability. The torque over the ankle joint was measured during the whole stretch. The angle and velocity at which the reflex was initiated was also determined. RESULTS: The electromyographic responses increased significantly at increasing stretch velocities (P<.001). The applied maximum angles are reproducible (intraclass correlation coefficient, .81) and provide representative torque responses. CONCLUSIONS: The assessment method of spasticity using full range passive movements provides objective outcomes. The angular velocity is responsible for an exponential increase in amplitude of the electromyographic response.

Adult↗

PubMed2005

Effect of augmented feedback on motor function of the affected upper extremity in rehabilitation patients: a systematic review of randomized controlled trials.

OBJECTIVE: Assessment of the available evidence regarding the effect of augmented feedback on motor function of the upper extremity in rehabilitation patients. METHODS: A systematic literature search was performed to identify randomized controlled trials that evaluated the effect of augmented feedback on motor function. Two reviewers systematically assessed the methodological quality of the trials. The reported effects were examined to evaluate the effect of therapeutic interventions using augmented feedback and to identify a possible relationship with patient characteristics, type of intervention, or methodological quality. RESULTS: Twenty-six randomized controlled trials were included, 9 of which reported a positive effect on arm function tests. Follow-up measurements were performed in 8 trials, 1 of which reported a positive effect. Different therapeutic interventions using augmented feedback, i.e. electromyographic biofeedback, kinetic feedback, kinematic feedback, or knowledge of results, show no difference in effectiveness. CONCLUSION: No firm evidence was found of effectiveness regarding the use of augmented feedback to improve motor function of the upper extremity in rehabilitation patients. Future studies should focus more on the content, form and timing of augmented feedback concerning the therapeutic intervention. It should be emphasized that motor learning effects can only be determined by re-examining the population after a follow-up period.

Arm↗

PubMed2005

Gait impairments in a group of patients with incomplete spinal cord injury and their relevance regarding therapeutic approaches using functional electrical stimulation.

The purpose of this study is to determine the most important impairments affecting the gait pattern of the incomplete spinal cord injury (SCI) patient and the potential impact of their treatment. The study consists of two parts. Firstly, a survey amongst 16 professionals was done to find out the impact of the impairments in incomplete-SCI patients. Secondly, gait data from 21 individuals were analyzed to determine the most common impairments. Frequently observed and relevant impairments were: inadequate hip extension (occurrence 76%), limited hip flexion (52%), limited knee flexion (71%), excess of plantar flexion (76%), and impaired foot contact (52%). In conclusion, for gait improvement in incomplete spinal cord injured patients not only ankle movements must be treated, which is done frequently, but also hip extension/flexion and knee flexion are important for gait restoration. The impact on the gait and potential solutions of these impairments are discussed.

Adolescent↗

PubMed2005

Use of information and communication technology in health care.

This report describes the possibilities of information and communication technology in healthcare. Attention is paid of how ICT can support the communication between health care professionals mutually as well as the communication between professionals and patients. Besides this some barriers that hampers implementation in everyday healthcare practice are described.

Communication↗

PubMed2005

Context aware tele-monitoring and tele-treatment services.

This report describes the Awareness project which attempts to make a step forward new kind of e-health services by realizing remote monitoring of health functions and by demonstrating the feasibility of free health treatment concepts; meaning monitoring and treatment independent of time and place utilizing a mobile service infrastructure.

Computer Systems↗

PubMed2004

Motor unit action potential rate and motor unit action potential shape properties in subjects with work-related chronic pain.

The objective of this study was to investigate differences in motor control of the trapezius muscle in cases with work-related chronic pain, compared to healthy controls. Ten cases with chronic pain and 13 controls participated in the study. Electromyographic (EMG) signals were recorded from the upper trapezius during five computer work-related tasks. Motor control was assessed using global root-mean-square value (RMS(G)), motor unit action potential (MUAP) rate (number of MUAPs per second, MR) and two MUAP shape parameters, i.e. root-mean-square (RMS(MUAP)) and median frequency (FMED(MUAP)). MR and FMED(MUAP) were higher for the cases than for the controls (P < 0.05). RMS(MUAP) showed a trend for higher values in the chronic pain group (P < 0.13), whereas RMS(G) did not show a significant difference between the groups. The higher MR, FMED(MUAP) and the trend for higher RMS(MUAP) suggest that more high-threshold MUs contribute to low-level computer work-related tasks in chronic pain cases. Additionally, the results suggest that the input of the central nervous system to the muscle is higher in the cases with chronic pain.

Action Potentials↗

PubMed2004

Predictive value of fear avoidance in developing chronic neck pain disability: consequences for clinical decision making.

OBJECTIVE: To improve clinical decision making in posttraumatic neck pain by investigating the additional value of fear-avoidance variables in predicting chronic neck pain disability. DESIGN: An inception cohort with baseline assessment 1 week posttrauma and outcome assessment 24 weeks posttrauma. Predictive factors include pain intensity, Neck Disability Index (NDI), catastrophizing, fear of movement (Tampa Scale for Kinesiophobia [TSK]), and avoidance muscle behavior. SETTING: Hospital emergency department of a general hospital. PARTICIPANTS: A consecutive sample of 90 people reporting of pain in neck or head region after a motor vehicle collision. Eighty-two subjects (91.1%) of the sample provided 24-week follow-up on the outcome. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURE: The NDI assessing physical disability of subjects with neck pain. RESULTS: By using a combination of the baseline NDI and TSK, it appears to be possible to predict chronic disability with a probability of 54.3% (95% confidence interval [CI], 35.2%-72.3%) after entering the NDI (cutoff, 15) as a first test, and with a probability of 83.3% (95% CI, 70.3%-91.3%) after entering the TSK (cutoff, 40) in a second test. CONCLUSIONS: A simple rating of baseline neck pain disability within a week of the trauma, separately or in combination with a test for fear of movement, can be used to predict future outcome. Patients showing fear of movement can be offered an intervention that focuses on reduction of this fear.

Adult↗

PubMed2004

Differences in outcome of a multidisciplinary treatment between subgroups of chronic low back pain patients defined using two multiaxial assessment instruments: the multidimensional pain inventory and lumbar dynamometry.

OBJECTIVE: To investigate the effects of a multidisciplinary back school programme (Roessingh Back Rehabilitation Programme, RRP) compared with usual care, as well as differences in treatment outcome between subgroups defined using two multiaxial assessment instruments: the Multidimensional Pain Inventory (MPI-DLV) and lumbar dynamometry. DESIGN: Randomized controlled trial. SETTING: Rehabilitation. SUBJECTS: One hundred and sixty-three patients with chronic, aspecific low back pain. INTERVENTION: All subjects were randomly assigned either to a multidisciplinary, physically oriented group treatment or to their usual care. MAIN OUTCOME MEASURES: The Roland Disability Questionnaire and health-related quality of life (EuroQol, EQ5-D) were measured as primary outcomes before randomization and after eight weeks and six months follow-up. RESULT: Only 30-50% of the patients in the RRP group showed improvement and this number is not significantly different from the control group. Subgroup analyses give some first indications that multiaxial measurement instruments can be used to identify subgroups with differences in treatment effects. CONCLUSION: The overall effect of a multidisciplinary treatment is disappointing, however multiaxial assessment before admission might be valuable in clinical practice, resulting in more effective treatments for patients with chronic low back pain.

Adult↗

PubMed2003

Effect of side dominance on myoelectric manifestations of muscle fatigue in the human upper trapezius muscle.

The purpose of this study was to investigate whether differences in the peripheral and control properties of the neuromuscular system due to long-term preferential use, related to side dominance, affect postural muscles, such as the upper trapezius. Therefore, fatigability properties of the upper trapezius muscles of the dominant and non-dominant side were assessed. Surface EMG signals were detected from the upper trapezius muscles of both sides of nine right- and five left-handed subjects with adhesive linear electrode arrays consisting of eight contact points. Static constant force contractions with the arms 90 degrees abducted were performed by the subjects while holding hand loads of 0 kg, 0.5 kg, and 1 kg. Surface EMG spectral and amplitude variables were computed from the recorded signals. EMG spectral variable rate of change (indicating fatigue) showed a statistically significant difference between the two sides, with the dominant side less fatigable than the non-dominant one. The observed differences held for both the right- and left-handed subject group. A possible explanation for the results is that long preferential use of one side with respect to the other leads to changes in muscle fiber membrane and control properties, in agreement with previous results on limb muscles.

Adult↗

PubMed2003

Chronic neck pain disability due to an acute whiplash injury.

Several theories about musculoskeletal pain syndromes such as whiplash-associated disorder (WAD) suggest that pain and muscle activity interact and may contribute to the chronicity of symptoms. Studies using surface electromyography (sEMG) have demonstrated abnormal muscle activation patterns of the upper trapezius muscles in the chronic stage of WAD (grade II). There are, however, no studies that confirm that these muscle reactions are initiated in the acute stage of WAD, nor that these muscle reactions persist in the transition from acute neck pain to chronic neck pain disability. We analyzed the muscle activation patterns of the upper trapezius muscles in a cohort of 92 subjects with acute neck pain due to a motor vehicle accident (MVA). This cohort was followed up in order to evaluate differences in muscular activation patterns between subjects who have recovered and those subjects who have not recovered following an acute WAD and developed chronic neck pain. sEMG parameters were obtained at 1, 4, 8, 12, and 24 weeks after an MVA. The level of muscle reactivity (the difference in pre- and post-exercise EMG levels) and the level of muscle activity during an isometric and a dynamic task were used as EMG parameters. The results revealed no elevated muscle reactivity either in the acute stage, or during the follow-up period. The results of both the isometric and dynamic task, showed statistically significant different EMG levels between four neck pain disability subgroups (analysis of variance reaching P-levels of 0.000), with an inverse relationship between the level of neck pain disability and EMG level. Furthermore, follow-up assessments of the EMG level during these two tasks, did not show a time related change. In conclusion, in subjects with future disability, the acute stage is characterized by a reorganization of the muscular activation of neck and shoulder muscles, possibly aimed at minimizing the use of painful muscles. This change of motor control, is in accordance with both the (neurophysiological) 'pain adaptation model' and (cognitive behavioral) 'fear avoidance model'.

Accidents, Traffic↗