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Biomedical subjects

H J Hermens

Publications and source records attributed to H J Hermens.

At least 19 recordsLinked to original sources
PubMed2005

Neuromuscular assessment in elderly workers with and without work related shoulder/neck trouble: the NEW-study design and physiological findings.

Musculoskeletal disorders in the neck and shoulder area are a major occupational concern in the European countries especially among elderly females. The aim was to assess these disorders based on quantitative EMG indicators and functional tests. 252 female computer users (45-68 years) were recruited from four European countries in two contrast groups: (1) 88 neck/shoulder (NS) cases reporting trouble in the neck and/or shoulder region for more than 30 days during the last year, and (2) 164 NS-controls reporting such trouble for no more than 7 days. Questionnaires, functional/clinical tests, and physiological recordings were performed in workplace related field studies. The results showed no differences in anthropometrics but NS-cases reported more strained head positions and more eye problems than controls. The psychosocial working factors were similar, although, NS-controls had slightly better scores on working conditions, general health, and vitality compared to cases. The NS-cases had lower maximal voluntary contraction (MVC) during shoulder elevation (mean (SD) 310 (122) N) compared to the controls (364 (122) N). During 30% MVC electromyography (EMGrms) in the trapezius muscle was lower in NS-cases (194 (105) muV) than in controls (256 (169) muV), while no differences were found regarding endurance time. Estimated conduction velocity was not different between NS-cases and -controls. Four functional computer tests were performed equally well by NS-cases and -controls, and the corresponding EMG variables also did not differ. A major finding in this large-scale epidemiological study is the significantly lower MVC in NS-cases compared with NS-controls together with lower EMGrms value at 30% MVC, while computer tasks were performed at similar relative muscle activation. The study was unable to reveal quantitative EMG indicators and functional tests that could objectively assess disorders in NS-cases.

Adult↗
PubMed2005

Comparison of the electromyographic activity in the upper trapezius and biceps brachii muscle in subjects with muscular disorders: a pilot study.

The aim of the present study was to investigate the extent to which work-related muscular disorders of the upper trapezius affect the activity of other pain-free muscles, in particular in the biceps brachii. Two groups of female subjects (age >43 years) participated in the study: seven affected subjects with self-reported disorders in the shoulder/neck region (cases) and nine healthy subjects (control group). Multi-channel electromyography (EMG) and force were recorded during maximum voluntary contractions (MVC) and during 6 min sustained contractions (at 30% MVC) of the upper trapezius and biceps brachii on the dominant side. From the EMG signals, the root mean square (RMS), median frequency (MDF) and single motor unit (MU) conduction velocity (CV) were estimated. From the force signal, the coefficient of variation was calculated. All data are presented as mean values and standard deviation. Differences between the cases and controls were found in the MVC force of the upper trapezius, which was lower in cases [253 (70) N] than in controls [357 (75) N], while the coefficient of variation of force during the sustained contraction was increased [cases 5.5 (2.2); controls 4.1 (1.9)]. The RMS (normalized to the RMS at MVC) during the 6 min sustained contractions was significantly lower in the cases than in the controls for both the upper trapezius and the biceps brachii. A tendency towards a smaller increase in the RMS with fatigue was only found in the trapezius muscle [slope: cases 6.5 (14.1) %/min, controls 10.2 (12.9) %/min]. No differences were found between the two subject groups with respect to the MDF and single MU CV in both muscles. While the lower RMS for the trapezius muscles of the cases may reflect changes at the local level, as well as in motor control, the lower biceps activity indicates a change in the central control strategies of the primarily unaffected muscle. Indications for a changed fatigability of the muscle were only found in the trapezius.

Case-Control Studies↗
PubMed2005

The effect of walking aids on muscle activation patterns during walking in stroke patients.

The purpose of this study was to investigate changes in muscle activation patterns with respect to timing and amplitude that occur when subjects with stroke walk with and without a walking aid. This knowledge could help therapists in deciding whether or not patients should use a cane or quad stick while walking. Thirteen patients suffering from a first unilateral ischemic stroke participated in the study. Surface electromyography (SEMG) of the erector spinae, gluteus maximus, gluteus medius, vastus lateralis, semitendinosus, gastrocnemius and tibialis anterior of the affected side were measured during three different conditions: (1) walking without a walking aid, (2) walking with a cane and (3) walking with a quad stick. Timing and amplitude parameters of the activation patterns were quantified using an objective burst detection algorithm and statistically evaluated. Results showed a statistically significant and clinically relevant decrease in burst duration of both erector spinae and tibialis anterior when walking with a cane. The amplitude of the vastus lateralis and tibialis anterior dropped when patients walked with a cane and quad stick. The use of a cane should be considered when therapy is given to stroke patients to achieve normal muscle activation patterns.

Adult↗
PubMed2004

The influence of different intermittent myofeedback training schedules on learning relaxation of the trapezius muscle while performing a gross-motor task.

The aim of this study was to investigate the influence of different intermittent myofeedback training schedules, as provided by a Cinderella-based myofeedback system, on learning relaxation and resistance to extinction of the trapezius muscle, in subjects performing a unilateral gross-motor task. Eighteen healthy subjects performed the task without and with feedback to study baseline and learning relaxation. Subsequently, resistance to extinction was investigated by performing the task without feedback. The gross-motor task consisted of continuously moving the dominant arm between three target areas at a constant pace. Subjects were randomly assigned into three groups, characterized by the sequence of feedback schedules with which the task was performed on 3 consecutive days. Auditory feedback was provided after a 5-, 10-, or 20-s interval when a pre-set level of 80% rest was not reached. Bipolar surface electromyography recordings performed at the dominant upper trapezius muscle were quantified using relative rest time (RRT) and root mean square (RMS) parameters. Learning relaxation was defined as an increase in RRT and a decrease in RMS values. Results showed the highest RRT levels as well as a decrease in RMS for the 10-s schedule. Additionally, the 10-s schedule was unique in its ability to elevate muscular rest above the 20% level, which may be considered relevant in preventing myalgia. None of the three schedules showed resistance to extinction. It was concluded that the 10-s interval was preferred over the 5- and 20-s schedules in learning trapezius relaxation in subjects performing a unilateral gross-motor task.

Adolescent↗
PubMed2004

Effects of electrode dislocation on electromyographic activity and relative rest time: effectiveness of compensation by a normalisation procedure.

Myofeedback seems a promising technique to treat myalgia related to computer work. A garment with embedded electrodes allows independent use by the subject. However, this inevitably results in electrode dislocations that can cause such variability in the electromyogram (EMG) parameters that the treatment fails. The objective was to investigate the variability introduced by electrode displacement on EMG root mean square (RMS) and relative rest time (RRT) and the effect of a normalisation procedure using a reference contraction to compensate for this. Dislocation was simulated using simultaneous recordings of pairs of electrodes situated 15mm apart on the trapezius muscle, surrounding a central electrode pair at the standard position. To assess sensitivity for electrode displacement, intra-subject variability was used. To assess the effects of normalisation, both intra and inter-subject variability were used. Results indicated a large sensitivity of RMS to electrode displacements, with no differences between typing (42%) and the reference task (43%). No systematic changes were found relative to a specific electrode dislocation. Normalisation of RMS resulted in a decrease in the sensitivity for electrode displacement (33%), but did not decrease inter-subject variability (27%). The median value of the intra-subject variability of RRT, using a fixed threshold, was 4.9%, whereas the normalised threshold did not decrease the intra-subject variability (7%). The results suggest that RRT is suitable for individual follow-up measurements and applications such as myofeedback, without the need for a normalisation procedure. The use of RMS requires considerably more care, owing to its large sensitivity to electrode displacement and lack of substantial effects of normalisation.

Adult↗
PubMed2004

Influence of hamstring lengthening on muscle activation timing.

The purpose of this study was to describe the changes in muscle activation patterns using surface electromyography (sEMG) during walking in patients with cerebral palsy (CP), before and after hamstring lengthening. In the current clinical use of sEMG during walking in CP for pre-operative planning, various authors have observed that timing of muscle activation patterns hardly changes after surgical intervention. This observation is based on tendon transfer studies and visual interpretation of raw EMG signals. Little is known about the effect of muscle lengthening on muscle activation patterns of the lengthened muscles and their antagonists. Fifteen children with CP comprising a total of 23 hamstring lengthenings were included in this study. Surface EMG of semitendinosus and vastus lateralis was measured before and after surgery. Timing parameters of the sEMG patterns were quantified, using an objective burst detection algorithm and statistically evaluated. Results showed that hamstring lengthening causes statistically significant differences in timing of both the semitendinosus and vastus lateralis. It is concluded that timing parameters of operated muscles and their antagonists after surgery do change. The delayed off-time of the semitendinosus and the decreased burst duration of the antagonist (the vastus lateralis) after surgery were the most important changes.

Adolescent↗
PubMed2004

Survey of the needs of patients with spinal cord injury: impact and priority for improvement in hand function in tetraplegics.

OBJECTIVE: To investigate the impact of upper extremity deficit in subjects with tetraplegia. SETTING: The United Kingdom and The Netherlands. STUDY DESIGN: Survey among the members of the Dutch and UK Spinal Cord Injury (SCI) Associations. MAIN OUTCOME PARAMETER: Indication of expected improvement in quality of life (QOL) on a 5-point scale in relation to improvement in hand function and seven other SCI-related impairments. RESULTS: In all, 565 subjects with tetraplegia returned the questionnaire (overall response of 42%). Results in the Dutch and the UK group were comparable. A total of 77% of the tetraplegics expected an important or very important improvement in QOL if their hand function improved. This is comparable to their expectations with regard to improvement in bladder and bowel function. All other items were scored lower. CONCLUSION: This is the first study in which the impact of upper extremity impairment has been assessed in a large sample of tetraplegic subjects and compared to other SCI-related impairments that have a major impact on the life of subjects with SCI. The present study indicates a high impact as well as a high priority for improvement in hand function in tetraplegics.

Activities of Daily Living↗
PubMed2004

The effect of an ankle-foot orthosis on walking ability in chronic stroke patients: a randomized controlled trial.

OBJECTIVE: Regaining walking ability is a major goal during the rehabilitation of stroke patients. To support this process an ankle-foot orthosis (AFO) is often prescribed. The aim of this study is to investigate the effect of an AFO on walking ability in chronic stroke patients. DESIGN: Cross-over design with randomization for the interventions. METHODS: Twenty chronic stroke patients, wearing an AFO for at least six months, were included. Walking ability was operationalized as comfortable walking speed, scores on the timed up and go (TUG) test and stairs test. Patients were measured with and without their AFO, the sequence of which was randomized. Additionally, subjective impressions of self-confidence and difficulty of the tasks were scored. Clinically relevant differences based on literature were defined for walking speed (20 cm/s), the TUG test (10 s). Gathered data were statistically analysed using a paired t-test. RESULTS: The mean difference in favour of the AFO in walking speed was 4.8 cm/s (95% CI 0.85-8.7), in the TUG test 3.6 s (95% CI 2.4-4.8) and in the stairs test 8.6 s (95% CI 3.1-14.1). Sixty-five per cent of the patients experienced less difficulty and 70% of the patients felt more self-confident while wearing the AFO. CONCLUSIONS: The effect of an AFO on walking ability is statistically significant, but compared with the a priori defined differences it is too small to be clinically relevant. The effect on self-confidence suggests that other factors might play an important role in the motivation to use an AFO.

Adult↗
PubMed2004

Distance training for the restoration of motor function.

We reviewed the literature on distance training for the restoration of motor function. Computerized literature searches were performed using the MEDLINE, EMBASE, Cinahl and Cochrane databases. Articles that met the criteria for inclusion were divided into three general areas concerning the type of training in relation to motor functions--muscle/joint, balance and cognition. From the publications identified in the literature search, 11 articles met the selection criteria. Six were related to muscle/joint functions, four to balance functions and one to cognitive functions. The articles were graded according to the strength of the scientific evidence they offered. The review revealed some promising applications of distance motor training, such as virtual reality (VR) and robotic devices. The strength of the evidence from these studies was poor, however, probably because the technology is relatively new. In contrast to the studies using VR and robotic devices, those using electromyographic (EMG) biofeedback showed a good to fair strength of scientific evidence. This can be explained by the substantial history of research on the restoration of motor function through the use of EMG biofeedback techniques. When implemented in clinical practice, these applications could reduce the pressure on scarce health-care resources.

Biofeedback, Psychology↗
PubMed2004

A feasibility study of remote consultation to determine suitability for surgery in stroke rehabilitation.

We studied knowledge transfer for the determination of the suitability of stroke patients for a specialist surgical procedure (split anterior tibial tendon transfer). Gait analysis data from patients at a general hospital were discussed with an expert in another country using personal computers, an ISDN connection (128 kbit/s) and TCP/IP-based communication tools. The key issue was whether the staff in the general hospital became better able to determine suitability for surgery. Twelve patients were studied. In three of the first four cases the advice of the remote expert changed the plan for surgery. After that the treatment plans did not change after consultation. After eight cases the local clinicians did not need to ask for further advice. There was a rapid increase in skill in determining suitability for surgery. The experience and skills of the local clinicians were thought to increase more rapidly than would have been the case without the consultations with a remote expert.

Clinical Competence↗
PubMed2003

The effect of an ergonomic computer device on muscle activity of the upper trapezius muscle during typing.

OBJECTIVE: Investigate whether an ergonomic computer device, characterised by an inclined working area and keyboard localisation close to the screen (the Up-Line), decreases the muscle activity of the upper trapezius muscle. METHODS: In a crossover design 19 healthy subjects and 19 patients with Whiplash Associated Disorder (WAD) typed during 10 min at the Up-Line and at a standard workstation with 15 min of rest in between. During typing surface EMG was measured of the trapezius muscle. The subjects were asked to rate sitting comfort and complaints. RESULTS: Although most subjects subjectively preferred the Up-Line, on average no significant differences were found in muscle activity between the two workstations for both patients and healthy subjects. Individually in 5 healthy subjects (25%) and in 6 patients (31%) muscle activity was lower when working at the Up-Line. CONCLUSION: Although some subjects subjectively prefer the Up-Line in sitting comfort, on average the Up-Line did not decrease the muscle activity, both in healthy subjects as in patients with WAD.

Adult↗
PubMed2003

Surface electromyography analysis for variable gait.

The surface electromyographic (SEMG) signal obtained during gait is often presented as the SEMG profile, the average SEMG activation pattern during one gait cycle. A disadvantage of this method is that it omits the step-to-step variability of the timing of the muscle activation patterns that might be relevant information as a performance measure of motor control and balance. In this paper, a method was used in which every step in the gait cycle could be analysed with respect to the timing of the muscle activation. For this purpose, the approximated generalised likelihood (AGLR) algorithm was implemented and tested. Results of the simulations show that the AGLR was much more accurate than a standard threshold criterion. Timing parameters could be calculated from a SEMG recording during gait and a measure for symmetry and coordination could be extracted. The amplitude distribution within and outside defined bursts is also presented to avoid the less precise classification into on and off patterns.

Algorithms↗
PubMed2002

Application of a dual channel peroneal nerve stimulator in a patient with a "central" drop foot.

Dropped foot is a common mobility problem amongst patients after a cerebro vascular accident. The condition arises from paresis of the muscles that control the foot movement during the swing phase of gait. If the abnormal movement is not compensated for, it results in a significant decrease in the mobility and hence quality of life. Compensation for the drop foot can be achieved through the application of functional electrical stimulation. To date, in the clinical environment, the stimulation has been applied through electrodes placed on the skin over the common peroneal nerve, and using a single channel implant device. It is well known that with these techniques it is difficult to establish a balanced response of the foot. An implantable dual channel system for stimulation of the deep and superficial peroneal nerve has now been developed for patients with a drop foot following a stroke. By stimulation of the two branches of the common peroneal nerve separately it is possible to achieve a precisely balanced dorsal flexion and eversion of the foot. Stimulation occurs via small bipolar electrodes which are placed subepineural. After successful tests on animals we have now started the two channel peroneal nerve stimulator implantation in patients. The preliminary results of the first implants are presented.

Cerebrovascular Disorders↗
PubMed2002

Assessment of activities of daily living with an ambulatory monitoring system: a comparative study in patients with chronic low back pain and nonsymptomatic controls.

OBJECTIVE: The aim of this study was twofold: (1) to investigate whether differences in activities of daily living exist between patients with chronic low back pain (CLBP) and nonsymptomatic controls; (2) to investigate the day-to-day variability in daily activities. DESIGN: Physical activities were measured over a 24-hour period with an ambulant monitoring system. SETTING: Measurements were carried out in the subject's own environment. SUBJECTS: Forty-seven CLBP patients and 10 nonsymptomatic controls participated in this study. RESULTS: On group level, CLBP patients show a lower activity pattern compared with controls, especially during the evening. This is reflected in a lower walking step frequency during the day and evening, more lying time during the day and a lower physical activity level, less standing time and more lying time during the evening. The day-to-day variability in activity pattern is high and similar for both the patient and control group. CONCLUSION: The lower activity level especially found during the evening might indicate that patients need all their capacity to perform the tasks imposed during the day and as a consequence have less capacity left for their leisure time, in general the evening. This suggests the existence of an imbalance between the patient's physical capacity and the imposed environmental load. The large but similar day-to-day variability in activity pattern, which does not support the clinical findings of 'bad days' in CLBP patients, suggests the need for repeated measures.

Activities of Daily Living↗
PubMed2001

Differences in treatment outcome between subgroups of patients with chronic low back pain using lumbar dynamometry and psychological aspects.

OBJECTIVE: To investigate whether subgroups of patients with chronic low back pain show differences in treatment outcome, measured with the Roland Disability Questionnaire. (RDQ). SETTING: The study was carried out in a rehabilitation centre. SUBJECTS: Eighty-four patients with chronic low back pain participated in this study. INTERVENTION: Patients followed a multidisciplinary treatment programme that primarily targets physical aspects. DESIGN AND MAIN OUTCOME MEASURE: Based on pretreatment lumbar dynamometry results and Symptom Checklist (SCL-90) scores, patients were divided into subgroups. The dynamometry subgroups were: performances lower than healthy subjects (expected performance), performances comparable with those of healthy subjects (normal performance) and inconsistent performances (submaximal performance). The SCL-90 subgroups were: a total score of 'average' or lower compared with a population of chronic pain patients (low psychological score) and a total score of 'above average' or higher compared with this population (high psychological score). Patients answered the RDQ in the week before (RDQ1; n = 84) and after treatment (RDQ2; n = 78) to investigate whether the subgroups show differences in outcome expressed as the percentage change between RDQ2 and RDQ1, (%RDQ2-1). A %RDQ2-1 > or = 20% was classified as an improvement. RESULTS: Improvement on disability level > or = 20% is shown in 64% and 55% of the patients with 'normal' and 'expected' lumbar dynamometry performances and low psychological scores compared with only 33% and 25% of those with high psychological scores. Patients with submaximal performances show hardly any changes in disability level and there are no differences betweenthose with low psychological scores (14%) and those reporting high scores (0%). CONCLUSION: The fact that patient subgroups with differences in treatment outcome can be defined using lumbar dynamometry and psychological questionnaires suggests that these instruments might facilitate treatment indication in clinical practice.

Adult↗
PubMed2000

Cervical muscle dysfunction in the chronic whiplash associated disorder grade II (WAD-II).

STUDY DESIGN: In a cross-sectional study, surface electromyography measurements of the upper trapezius muscles were obtained during different functional tasks in patients with a chronic whiplash associated disorder Grade II and healthy control subjects. OBJECTIVES: To investigate whether muscle dysfunction of the upper trapezius muscles, as assessed by surface electromyography, can be used to distinguish patients with whiplash associated disorder Grade II from healthy control subjects. SUMMARY OF BACKGROUND INFORMATION: In the whiplash associated disorder, there is need to improve the diagnostic tools. Whiplash associated disorder Grade II is characterized by the presence of "musculoskeletal signs." Surface electromyography to assess these musculoskeletal signs objectively may be a useful tool. METHODS: Normalized smoothed rectified electromyography levels of the upper trapezius muscles of patients with whiplash associated disorder Grade II (n = 18) and healthy control subjects (n = 19) were compared during three static postures, during a unilateral dynamic manual exercise, and during relaxation after the manual exercise. Coefficients of variation were computed to identify the measurement condition that discriminated best between the two groups. RESULTS: The most pronounced differences between patients with whiplash associated disorder Grade II and healthy control subjects were found particularly in situations in which the biomechanical load was low. Patients showed higher coactivation levels during physical exercise and a decreased ability to relax muscles after physical exercise. CONCLUSIONS: Patients with whiplash associated disorder Grade II can be distinguished from healthy control subjects according to the presence of cervical muscle dysfunction, as assessed by surface electromyography of the upper trapezius muscles. Particularly the decreased ability to relax the trapezius muscles seems to be a promising feature to identify patients with whiplash associated disorder Grade II. Assessment of the muscle (dys)function by surface electromyography offers a refinement of the whiplash associated disorder classification and provides an indication to a suitable therapeutic approach.

Adult↗