Hermanus J. Hermens

Development of recommendations for SEMG sensors and sensor placement procedures

The knowledge of surface electromyography (SEMG) and the number of applications have increased considerably during the past ten years. However, most methodological developments have taken place locally, resulting in different methodologies among the different groups of users.A specific objective of the European concerted action SENIAM (surface EMG for a non-invasive assessment of muscles) was, besides creating more collaboration among the various European groups, to develop recommendations on sensors, sensor placement, signal processing and modeling. This paper will present the process and the results of the development of the recommendations for the SEMG sensors and sensor placement procedures. Execution of the SENIAM sensor tasks, in the period 1996-1999, has been handled in a number of partly parallel and partly sequential activities. A literature scan was carried out on the use of sensors and sensor placement procedures in European laboratories. In total, 144 peer-reviewed papers were scanned on the applied SEMG sensor properties and sensor placement procedures. This showed a large variability of methodology as well as a rather insufficient description. A special workshop provided an overview on the scientific and clinical knowledge of the effects of sensor properties and sensor placement procedures on the SEMG characteristics. Based on the inventory, the results of the topical workshop and generally accepted state-of-the-art knowledge, a first proposal for sensors and sensor placement procedures was defined. Besides containing a general procedure and recommendations for sensor placement, this was worked out in detail for 27 different muscles. This proposal was evaluated in several European laboratories with respect to technical and practical aspects and also sent to all members of the SENIAM club (>100 members) together with a questionnaire to obtain their comments. Based on this evaluation the final recommendations of SENIAM were made and published (SENIAM 8: European recommendations for surface electromyography, 1999), both as a booklet and as a CD-ROM. In this way a common body of knowledge has been created on SEMG sensors and sensor placement properties as well as practical guidelines for the proper use of SEMG.

Spasticity: Clinical perceptions, neurological realities and meaningful measurement

The aim of this paper is to review briefly our understanding of the phenomenon of spasticity based in current evidence.

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.

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.

Neurophysiological methods for the assessment of spasticity: The Hoffmann reflex, the tendon reflex, and the stretch reflex

Purpose: To review the literature concerning neurophysiological methods to assess spasticity with respect to mechanisms and methodology, and to describe the three most commonly used methods: the Hoffmann reflex (H-reflex), the Tendon reflex (T-reflex), and the Stretch Reflex (SR). Method: A systematic internet database search was performed to identify neurophysiological measurement methods of spasticity. A systematic exclusion procedure resulted in 185 included references, completed by additional informal search. For this paper, information about the H-, T- and stretch reflexes was extracted from these references. Results: Although the reflexes are basically monosynaptic, there are many supraspinal pathways which modulate the responses in terms of their amplitude and latency. As a consequence the methods are sensitive to a considerable number of experimental conditions and are characterized by a moderate reliability and sensitivity. Correlations with other (i.e. biomechanical, neurophysiological or clinical) spasticity assessment parameters are moderate to poor. Standardised and broadly accepted protocols are still largely lacking preventing an effective exchange of knowledge. Conclusions: The clinical and experimental use of the three methods is restricted due to moderate reliability and sensitivity. It is recommended to perform combined neurophysiological - biomechanical assessment of spasticity during active, functional movement.

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.

Cervical muscle dysfunction in chronic whiplash-associated disorder grade 2: the relevance of the trauma.

Study Design. Surface electromyography measurements of the upper trapezius muscles were performed in patients with a chronic whiplash-associated disorder Grade 2 and those with nonspecific neck pain. Objective. To determine the etiologic relation between acceleration–deceleration trauma and the presence of cervical muscle dysfunction in the chronic stage of whiplash-associated disorder. Summary of Background Information. From a biopsychosocial perspective, the acceleration–deceleration trauma in patients with whiplash-associated disorder is not regarded as a cause of chronicity of neck pain, but rather as a risk factor triggering response systems that contribute to the maintenance of neck pain. One of the contributing factors is dysfunction of the cervical muscles. Considering the limited etiologic significance of the trauma, it is hypothesized that in patients with neck pain, there are no differences in muscle activation patterns between those with and those without a history of an acceleration–deceleration trauma. Methods. Muscle activation patterns, expressed in normalized smooth rectified electromyography levels of the upper trapezius muscles, in patients with whiplash-associated disorder Grade 2 were compared with those of patients with nonspecific neck pain. The outcome parameters were the mean level of muscle activity before and after a physical exercise, the muscle reactivity in response to the exercise, and the time-dependent behavior of muscle activity after the exercise. Results. There were no statistical significant differences in any of the outcome parameters between patients with whiplash-associated disorder Grade 2 and those with nonspecific neck pain. There was only a tendency of higher muscle reactivity in patients with whiplash-associated disorder Grade 2. Conclusions. It appears that the cervical muscle dysfunction in patients with chronic whiplash-associated disorder Grade 2 is not related to the specific trauma mechanism. Rather, cervical muscle dysfunction appears to be a general sign in diverse chronic neck pain syndromes.

Energy storage and release of prosthetic feet Part 1: biomechanical analysis related to user benefits

The energy storing and releasing behaviour of 2 energy storing feet (ESF) and 2 conventional prosthetic feet (CF) were compared (ESF: Otto Bock Dynamic Pro and Hanger Quantum; CF: Otto Bock Multi Axial and Otto Bock Lager). Ten trans-tibial amputees were selected. The study was designed as a double-blind, randomised trial. For gait analysis a VICON motion analysis system was used with 2 AMTI force platforms. A special measuring device was used for measuring energy storage and release of the foot during a simulated step. The impulses of the anteroposterior component of the ground force showed small, statistically non-significant differences (deceleration phase: 22.7–23.4 Ns; acceleration phase: 17.0–18.4 Ns). The power storage and release phases as well as the net results also showed small differences (maximum difference in net result is 0.03 J kg−1). It was estimated that these differences lead to a maximum saving of 3% of metabolic energy during walking. It was considered unlikely that the subjects would notice this difference. It was concluded that during walking differences in mechanical energy expenditure of this magnitude are probably not of clinical relevance. Ankle power, as an indicator for energy storage and release gave different results to the energy storage and release as measured with the special test device, especially during landing response. In the biomechanical model (based on inverse dynamics) used in the gait analysis the deformation of the material is not taken into consideration and hence this method of gait analysis is probably not suitable for calculation of shock absorption.

Is rectus femoris really a part of quadriceps? Assessment of rectus femoris function during gait in able-bodied adults

There is conflicting evidence as to the precise activation pattern of the rectus femoris (RF) muscle during gait in able-bodied subjects. The aim of this study was to determine precise activation pattern of RF during gait in a healthy adult population. Surface and fine wire EMG from RF and vastus lateralis (VL) were recorded simultaneously at different walking speeds in five able-bodied subjects. The results of fine wire EMG showed that, at normal walking speed, RF was active only during the stance-to-swing transition. At faster speeds, increased levels of RF activity were seen during the same transition period. At the fastest speed, there was some activity during terminal stance, in addition to that at stance-to-swing transition, that could be attributed to rapid hip extension and thereby a rapid stretch of RF. However, the RF surface EMG signal was found to exhibit a bi-phasic pattern whilst walking at all different self-selected speeds. A burst of EMG activity recorded at initial contact on the surface signal but not on fine wire EMG, was due to cross-talk from vastus intermedius (VI). A close similarity was observed between the surface EMG patterns of VL and RF. VL surface and fine wire EMG profiles were identical for all the self-selected speeds with a main peak of activity beginning in terminal swing and ceasing in mid-stance. We conclude that RF is active only during stance-to-swing transition and the activity during swing-to-stance transition, as described in the literature, is very probably due to cross-talk.

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-today 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 subjects 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 re‘ected 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 patients 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.