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Biomedical subjects

H Hermens

Publications and source records attributed to H Hermens.

9 recordsLinked to original sources
PubMed2005

Comparative assessment of study groups of elderly female computer users from four European countries: questionnaires used in the NEW study.

There is a lack of consistent and comprehensive questionnaire forms for the studies of factors associated with work-related musculoskeletal disorders at the European level. One of the results of the EU-funded project, neuromuscular assessment in the elderly worker (NEW), is a set of questionnaires for the screening of musculoskeletal status and the studies of factors that are believed to affect musculoskeletal health. The questionnaires have been used among elderly women (45+) in different occupations and organisations in Denmark, The Netherlands, Sweden and Switzerland. The aim of this short communication is to present the questionnaires used in the NEW study and to evaluate the appropriateness of pooling data gathered in each participating country into a common database. It is concluded that although differences exist among the study samples, these are not of such a magnitude or pattern that data from the four groups cannot be pooled. The questionnaires are available in Danish, Dutch, English, German and Swedish.

Case-Control Studies↗
PubMed2005

Rectus femoris surface myoelectric signal cross-talk during static contractions.

The clinical application of EMG requires that the recorded signal is representative of the muscle of interest and is not contaminated with signals from adjacent muscles. Some authors report that surface EMG is not suitable for obtaining information on a single muscle but rather reflects muscle group function [J. Perry, C.S. Easterday, D.J. Antonelli, Surface versus intramuscular electrodes for electromyography of superficial and deep muscles. Physical Therapy 61 (1981) 7-15]. Other authors report however, that surface EMG is adequate to determine individual muscle function, once guidelines pertaining to data acquisition are followed [D.A. Winter, A.J. Fuglevand, S.E. Archer. Cross-talk in surface electromyography: theoretical and practical estimates. Journal of Electromyography and Kinesiology 4 (1994) 15-26]. The aim of this study was to determine whether surface EMG was suitable for monitoring rectus femoris (RF) activity during static contractions. Five healthy subjects, having given written informed consent, participated in this trial. Surface and fine wire EMG from the rectus femoris and the vastus lateralis (VL) muscles were recorded simultaneously during a protocol of static contractions consisting of knee extensions and hip flexions. Ratios were used to quantify the relationship between the surface EMG amplitude value and the fine wire EMG amplitude value for the same contraction. The results showed that hip flexion contractions elicited RF activation only and that knee extension contractions elicited fine wire activity in VL only. When the relationship between RF surface and RF fine wire electrodes was compared for hip flexion and knee extension contractions, it was observed that for all subjects, there was a tendency for increased RF surface activity in the absence of RF fine wire activity during knee extensions. It was concluded that the activity recorded by the RF surface electrode arrangement during knee extension consisted of EMG from the vastii, i.e., cross-talk and that vastus intermedius was the most likely origin of the erroneous signal. Therefore it is concluded that for accurate EMG information from RF, fine wire electrodes are necessary during a range of static contractions.

Adult↗
PubMed2004

Performance specification for lower limb orthotic devices.

OBJECTIVE: To establish the range of forces and moments applied to lower limb orthoses during ambulation by routine users. DESIGN: Well-established gait analysis techniques were used to determine the loading at the major joints. It was assumed that the joint moments were transmitted by the orthosis encompassing any particular joint. Two hundred and five assessments of 164 patients were successfully completed by a consortium of four gait laboratories in Europe. The orthosis specification and patient clinical data were also recorded. BACKGROUND: The design and development of orthoses has occurred largely by evolution rather than by formal engineering methods. In particular, formal design has been hampered by a lack of information on the forces and moments applied during ambulation. METHODS: A standard gait analysis procedure was employed to capture the data. In-house biomechanical models were used to calculate the joint loading. Data were normalised with respect to patient weight and leg length. RESULTS: It was found that the median maximum normalised ankle moment transmitted by an ankle foot orthosis was 0.15 and the maximum knee moment was 0.09. The greatest moment transmitted by the hip joint of a hip knee ankle foot orthosis was also 0.09. There was a wide variation in the data due to differences in the impairments of the test subjects. CONCLUSION: It is possible to estimate the loads transmitted by an orthosis using established gait analysis procedures without the need for load measurement transducers. There is now a need both to collect a larger representative dataset and to perform validation studies with transducers.

Adolescent↗
PubMed2004

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.

Adult↗
PubMed2003

Three dimensional inertial sensing of foot movements for automatic tuning of a two-channel implantable drop-foot stimulator.

A three dimensional inertial sensing system for measuring foot movements during gait is proposed and tested. It can form the basis for an automated tuning system for a two-channel implantable drop-foot stimulator. The foot orientation and position during the swing phase of gait can be reconstructed on the basis of three-dimensional measurement of acceleration and angular velocity, using initial and final conditions during mid-stance. The foot movements during gait of one stroke person using the implanted two-channel stimulator were evaluated for several combinations of stimulation parameters for both channels. The reconstructed foot movements during gait in this person indicated that the channel stimulating the deep peroneal nerve contributes mainly to dorsiflexion and provides some reduction of inversion seen without stimulation, while the channel activating the superficial peroneal nerve mainly provides additional reduction of inversion. This agrees with anatomical knowledge about the function of the muscles activated by both branches of the peroneal nerve. The inertial sensor method is expected to be useful for the clinical evaluation of foot movements during gait supported by the two-channel drop-foot stimulator. Furthermore, it is expected to be applicable for the automated balancing of the two stimulation channels to ensure optimal support of gait.

Acceleration↗
PubMed1995

Sacral anterior root stimulation for bladder control in patients with a complete lesion of the spinal cord.

A Finetech-Brindley bladder controller was implanted in 17 patients with a complete lesion of the spinal cord. During a microscopic procedure in the cauda equina, the sacral roots were identified and the posterior components of the S2, S3 and S4 roots were cut. The stimulator was placed intradurally around the anterior components of the S2, S3, S4 roots and the S5 root. Our patients have now been followed-up for periods varying between 1 and 6 years. In all 17 patients, the bladder capacity has been increased; 16 patients have a residual volume of less than 30 ml, urinary tract infection is rare; 12 patients are fully continent. All male patients can achieve a full sustained erection by means of the implant and 13 patients are using the implant for bowel function. The method has no significant harmful effects or complications.

Adult↗
PubMed1990

Electromyogram power spectra frequencies associated with motor unit recruitment strategies.

The isolated contributions of motor unit recruitment and firing rate variations to the median frequency of the electromyogram's power density spectrum were determined. Orderly stimulation of the cat gastrocnemius motor units via nerve electrodes gave rise to linearly increasing median frequency regardless of the action potential firing rate of the active motor units. Increase in the discharge rate of all the motor units resulted in nearly constant median frequency. It was concluded that the increasing average conduction velocity during motor unit recruitment is the major contributor to variations in the electromyogram median frequency. The possibility of using the median frequency as the index to identify the recruitment control strategies employed by various muscles during increasing force contraction is suggested.

Action Potentials↗