PubMed Health⌕ Search

Biomedical subjects

B Gerdle

Publications and source records attributed to B Gerdle.

At least 37 records · Page 2Linked to original sources
PubMed1999

Reproducibility of surface EMG during dynamic shoulder forward flexions: a study of clinically healthy subjects.

There is a shortage of studies concerning the reproducibility of surface electromyography (EMG) during dynamic contractions. The movement per se introduces factors that could have the potential to affect the characteristics of the electromyogram. The aim of this study was to investigate the during-the-day reproducibility (using intra-class coefficient, ICC) of the peak torque (PT) and the EMG variables (without removing electrodes) of dynamic shoulder forward flexions. Eleven healthy women performed three sets of 10 dynamic maximum right-shoulder flexions at 1 h intervals using an isokinetic dynamometer. The PT of each flexion was determined. EMG signals were recorded from four muscles (trapezius, deltoid, infraspinatus and biceps brachii) using surface electrodes, and the mean frequency of the power spectrum (MNF [Hz]) and the signal amplitude (RMS [microV]), were computed. The ability to relax between maximum flexions was calculated as a ratio between the RMS during the passive extension phase and the RMS during the active flexion phase of each contraction cycle. This ratio is the signal amplitude ratio (SAR). The present study showed good reproducibility for PT, MNF and RMS, while the reproducibility of SAR was generally acceptable (fair) according to the criteria used.

Adult↗
PubMed1999

The relationships between spinal sagittal configuration, joint mobility, general low back mobility and segmental mobility in female homecare personnel.

The aim of this study was to investigate joint mobility, segmental and general spinal mobility and their interrelationship in 607 women working as homecare personnel. Joint mobility (mainly peripheral) was estimated using the "Beighton" score. Spinal posture and mobility were measured by Debrunner's kyphometer. Passive segmental mobility and pain provocation were estimated manually. Reliability tests between two physiotherapists of segmental mobility and pain provocation (n = 150 subjects) were performed. Positive correlations were found between joint mobility, sagittal thoraco-lumbar mobility and segmental mobility. Hyperlordosis (>39 degrees) was associated with greater lumbar mobility. The reliability of manual segmental mobility and segmental pain provocation was good, especially in the lowest back segments (kappa approximately 0.7). Joint mobility, general mobility and segmental spinal mobility intercorrelated. Segmental mobility manually estimated showed intertester reliability. The good positive correlation between sagittal lumbar mobility and manually tested segmental mobility indicates criterion validity for the latter.

Adult↗
PubMed1998

[Spectrum of sequelae after whiplash injury. Localization and development in relation to the clinical picture].

Neck sprain, a common sequela of motor vehicle trauma, is characterised by soft tissue lesions in the facet joints (the capsule), cervical discs (the annulus), ligaments, muscles, and sometimes in the nerve roots or the central nervous system. The cardinal manifestation of whiplash injury is neck pain, which may arise from any innervated part of the injured joints or muscles except the disc nucleus, the articular surface of facet joints, or the flaval ligaments. Pain may be referred to the skin or muscles via the respective sensory nerves. The tissue lesions, together with post-traumatic nerve root degeneration or medullary compression, may give rise to the complex neck sprain syndrome. Localisation of the source of symptoms by means of meticulous physical examination, MRI (magnetic resonance imaging), or accurately sited local anaesthetic injections is described in the article, and operative and multimodal rehabilitation procedures are discussed.

Accidents, Traffic↗
PubMed1998

Worsening of neck and shoulder complaints in humans are correlated with frequency parameters of electromyogram recorded 1-year earlier.

The aim was to investigate whether output and electromyogram (EMG) variables obtained from an isokinetic endurance test of the shoulder flexor muscles of 23 women with neck and shoulder problems in a car and truck industry correlated with improvement or worsening of complaints 1 year later. Each subject performed 100 maximal isokinetic shoulder forward flexions at 60 degrees x s(-1). Surface EMG of the trapezius, deltoid, biceps brachii and infraspinatus muscles and mechanical output (peak torque) were determined for each contraction. The EMG was used to determine mean frequency fmean and the ratio between the signal amplitudes of the EMG of the passive relaxation and active flexion parts of each contraction cycle (SAR). The subjects also rated the degree of fatigue they experienced throughout the test. The magnitude of the shift in fmean was correlated with whether improvement or worsening occurred for complaints in the neck and or shoulders; a significant relationship (r2 = 0.44; P = 0.001) existed between the total frequency shift of the four muscles and the variables measuring improvement in complaints. In the multivariate predictions other fmean variables and perception of fatigue were also of significance. The present study would indicate that a high degree of fmean shift correlates with improvement in neck and shoulder complaints 1 year later. One possible reason could be that fmean reflects the muscle morphology and/or a pathological situation for the type-1 muscle fibres.

Adult↗
PubMed1998

One-year reproducibility and stability of the signal amplitude ratio and other variables of the electromyogram: test-retest of a shoulder forward flexion test in female workers with neck and shoulder problems.

We have studied 23 women with neck and shoulder problems in a car factory with a 1-year interval. Our main aim was to investigate the reproducibility and stability of the tension pattern. In addition, the mean frequency (MNF) of the power spectrum and the signal amplitude (RMS) of the surface electromyograph (EMG) of the trapezius, deltoid and infraspinatus muscles and mechanical output were determined throughout 100 maximal isokinetic shoulder forward flexions. The signal amplitude ratio (SAR) was calculated as the ratio between the signal amplitude of the EMG of the passive relaxation and the active flexion part of each contraction cycle. The SAR variable can be reproduced (r = 0.47-0.76) with a 1-year interval. There was a significantly lower SAR of the trapezius at the second test, which might have been due to lower work pace at the factory. The longitudinal patterns of SAR throughout the two tests were similar at both tests. There were significant correlations between tests for 18 out of 22 EMG variables, even though the correlations were generally lower than for SAR (initial MNF: r = 0.39-0.48; MNF endurance level: r = 0.55-0.83; RMS (%): r = 0.08-0.46). Peak torque had better reproducibility than work. In conclusion, SAR has a long-term reproducibility equal to or better than other EMG and biomechanical variables. The present results indicate that SAR has potential to measure unnecessary muscle tension in intervention studies and to identify individual movement patterns.

Electromyography↗
PubMed1998

Repeated maximum reciprocal knee movements in patients with minimal overt symptoms after ischaemic stroke: an evaluation of mechanical performance and EMG.

The ability to perform reciprocal knee flexions and knee extensions was investigated in patients with minimal or no overt motor symptoms after stroke. Ten patients and 22 controls performed 10 maximal reciprocal knee extensions and knee flexions without intervening rest period using an isokinetic dynamometer (Cybex II). Peak torque (PT; Nm), signal amplitude (RMS) and mean frequency (fmean) of the electromyography were registered for each extension and flexion separately and as the ratio extension/flexion. The patients exhibited pronounced motor deficit despite no or minimal overt clinical symptoms. The reduced motor capacity in the knee muscles was shown as a decrease in the PT and in a different electromyographic pattern compared with the controls. A bilateral affection was found with the formerly hemiparetic side mostly affected. Repeated reciprocal contractions influenced the motor performance, shown as an increase of the PT ratio in the patients, which was especially pronounced with an increasing number of contractions.

Adult↗
PubMed1998

Physical and psychosocial work-related risk factors associated with musculoskeletal symptoms among home care personnel.

The aim of this cross-sectional study was to investigate physical and psychosocial aspects of the work environment, sociodemographic data and certain lifestyle factors, and the relationship between these variables and complaints in the shoulder/neck and low back area among female home care personnel. A questionnaire was completed by 361 randomly selected women. Multiple logistic regression analyses were conducted to evaluate the importance of several exposure factors for complaints in the shoulder/neck and low back areas. The results of this study clearly indicate that 'standing in forward-bent and twisted postures' can be viewed as a risk factor for shoulder/neck pain. A combination of this physical exposure and 'no possibility of influencing the planning of work' gave an increase in odds ratio, indicating an interaction between these two exposure indices. However, this interaction was not found for low back pain. 'Standing in forward-bent and twisted postures', 'standing in awkward positions' and whether the subject had children staying at home were significantly correlated to complaints about the low back. In fact, the latter factor decreased the risk of having complaints. The results indicated that certain physical and psychosocial work risk factors could influence shoulder/neck and low back pain.

Adult↗
PubMed1997

Inter-relationship between muscle morphology, mechanical output and electromyographic activity during fatiguing dynamic knee-extensions in untrained females.

Changes in mechanical performance and electromyographic activity during fatiguing dynamic knee-extensions were evaluated with respect to muscle fibre type composition of the vastus lateralis muscle in nine sedentary female [23 (3) years] volunteers. The subjects performed 150 repetitive maximum knee-extensions using a Cybex dynamometer at 1.57 rad x s(-1). EMG activity was recorded from the vastus lateralis, the vastus medialis and the rectus femoris muscles. For each contraction, mean power frequency (MPF) and the root mean square (RMS) of the EMG were calculated, simultaneously with the peak torque (PT), contractional work (CW) and the mean power (MP). The MPF showed an initial decrease followed by a stable phase. The RMS increased during the initial seven contractions, after which a period of variability was displayed until about the 60th contraction. At the plateau level (last 50 contractions) the relative RMS values were not significantly different from the initial values. The PT, CW and MP increased during the initial five to ten contractions, after which a two-phase pattern was displayed, with a gradual decline followed by a stable phase. The absolute plateau level of MPF for the vastus lateralis muscle showed a significant negative correlation with the area percentage of type-1 fibres (r = -0.71). Significant correlations were also demonstrated to occur between the absolute plateau levels of PT, CW and MP and the relative proportion of type-1 fibres (r = 0.80, r = 0.82 and r = 0.82 respectively). Thus, in female subjects the mechanical performance and the MPF during fatigue are at least partly determined by muscle morphology.

Adult↗
PubMed1997

The relationships between EMG and muscle morphology throughout sustained static knee extension at two submaximal force levels.

This study investigated the relationship between muscle morphology and surface electromyographic parameters (mean frequency, f(mean); and signal amplitude, RMS) during sustained static knee extension to exhaustion at 25% maximal voluntary contraction (MVC) and at 70% MVC. Twenty clinically healthy subjects participated. EMGs were registered from the quadriceps. Muscle forces during knee extension at a 90 degree joint angle were maintained at the respective levels throughout the measurement periods. A biopsy was obtained of the vastus lateralis muscle. The total time to exhaustion was normalized for each subject. By means of regression analysis, the intercept (i) (i.e. the unfatigued state) and the regression coefficient (k) were determined for each EMG parameter. The endurance time increased with decreasing force level. A significantly higher perception of fatigue was found at 25% MVC than at 70% MVC. From principal component analyses it was concluded that RMS-k at 25% MVC mainly correlated with the type 2 muscle fibre proportions (%), and at 70% MVC mainly with the areas of type 2 muscle fibre. At 25% MVC, f(mean)-k correlated with the areas of type 2A, 2B and 2C fibres, and at 70% MVC negatively with the proportion of type 2B and to some extent with areas of type 2A, 2B and 2C fibres. f(mean)-i at 25% MVC correlated with fibre type proportions (%); f(mean)-i at 70% MVC correlated with the areas of type 2A, 2B and 2C. The present study indicates relationships between surface EMG and muscle morphology, which is contrary to presented models of the EMG.

Adult↗
PubMed1997

Differential responses in intramuscular pressure and EMG fatigue indicators during low- vs. high-level isometric contractions to fatigue.

This study investigated changes in intramuscular pressure (IMP) and surface electromyographic (EMG) parameters (mean frequency of the power spectrum, f(mean); and signal amplitude denoted as root mean square, RMS) during contractions to fatigue at 25 and 70% of maximal voluntary contraction (MVC). Parameters were recorded simultaneously from the vastus lateralis muscle during knee extension. A significant decrease in f(mean) occurred with time at both contraction levels; however, the rate of decline (slope) was greater at 70% MVC. RMS increased throughout the contractions at both levels, with the relative increase being significantly greater for 25% MVC. IMP increased during 25% MVC but did not change during the 70% MVC contraction. IMP at rest was significantly higher post-contractions than it was pre-contractions at 25% MVC (21.1 vs. 8.0 mmHg, P < 0.01) and 70% MVC (13.7 vs. 8.6 mmHg, P < 0.01). Consequently, post-contraction IMP was higher at 25% MVC than at 70% MVC (P < 0.01). IMP changes throughout the fatiguing contractions correlated negatively with f(mean) and positively with RMS at both MVC levels; however, these correlations were better at 25% MVC. The extent of intramuscular water accumulation is discussed as a major cause of the difference in IMP changes between 25% and 70% MVC. Significant differences in the rate of change for all parameters between high vs. low contraction levels may suggest a common mechanism governing changes in IMP and EMG fatigue indicators.

Adult↗
PubMed1997

Skeletal muscle fatigue and endurance in young and old men and women.

The effects of increasing age on skeletal muscle fatigue and endurance were assessed in 22 healthy young (14 men and 8 women; mean age, 28 +/- 6 years) and 16 healthy old (8 men and 8 women; mean age, 73 +/- 3 years) individuals. All subjects performed 100 repeated maximum dynamic knee extensions at 90 degrees.s-1 (1.57 rad.s-1) using an isokinetic dynamometer (Cybex II). Peak torque was recorded during every contraction, and for each individual the maximal voluntary contraction (MVC), the fatigue rate, the endurance level, and the relative reduction in muscle force were determined. MVC and endurance level were significantly lower in old men and women, but there was no discernible difference in relative muscle force reduction and fatigue rate between young and old individuals. We conclude that thigh muscles of older individuals are weaker than those of younger individuals, but relative to their strength, older individuals have similar properties as younger individuals with respect to muscle fatigue and endurance.

Adult↗
PubMed1995

Knee extensor performance of dominant and non-dominant limb throughout repeated isokinetic contractions, with special reference to peak torque and mean frequency of the EMG.

The aim of this study was to investigate whether significant differences in peak torque (PT), mean power frequency of EMG (fmean) and perceived fatigue exist between the dominant and non-dominant knee extensors throughout repeated contractions. The present study forms part of a research project aimed at developing tests for the determination of the degree of motor control in patients with sequelae after CNS injury. A total of 22 clinically healthy subjects (14 males and eight females) took part in the investigation. The subjects performed endurance tests of the lower limbs, consisting of 100 repeated knee extensions using a Cybex dynamometer at 1.57 rad s-1. The patterns of PT, fmean and perception of fatigue throughout the endurance test were investigated. The endurance curves of PT and fmean showed, in common with other studies, an initial steep decrease followed by a stable phase. No significant differences existed between dominant and non-dominant knee extensors with regard to PT, fmean or perception of fatigue. The results indicate that it may be possible to use the contralateral knee extensors as an indicator of motor recovery in hemiplegia in patients with a high degree of recovery.

Adult↗
PubMed1994

The temporal occurrence of the mean power frequency shift of the electromyogram during maximum prolonged dynamic and static working cycles.

The study investigated the temporal occurrence of the mean power frequency shift (MPF) of the EMG during prolonged (dynamic and static) working cycles. Ten healthy subjects took part in the experiment. The experimental protocol required each subject to first complete 70 maximum isokinetic knee extensions at 90 degrees s-1). Without any rest, the subject then performed a maximum static knee extension with the dynamometer positioned at 45 degrees of flexion until subjective exhaustion. This sequence of dynamic and static exercise was repeated two more times with a 5-min rest interval preceding each sequence. The EMG signal of the rectus femoris was obtained simultaneously with the torque signal (PT) from the dynamometer. Dynamic contractions PT and MPF decreased throughout the three dynamic periods. Patterns composed of two phases were found; first an initial steep decrease during the first 40 contractions followed by a less steep decrease. Static contractions PT decreased significantly during the three static contractions. Significant (small) decreases in MPF occurred only during the second and third static contractions. Since the major part of the MPF shift occurred early in the exhaustive performance, it is questioned whether the MPF shift detects peripheral fatigue of the type 1 fibers.

Adult↗
PubMed1994

Endurance training in patients with multiple sclerosis: five case studies.

BACKGROUND AND PURPOSE: The purpose of this report is to describe how patients with multiple sclerosis increased the isokinetic peak torque of their knee flexors and perceived well-being after an endurance training program. SUBJECTS AND METHODS: Five patients trained for 4 to 6 weeks using an endurance program for the lower extremities. Before and after training, the subjects performed 50 repeated maximum knee flexions, with simultaneous recording of surface electromyographic activity of two knee flexors, on 3 separate days using an isokinetic dynamometer. Throughout the tests, the subjects rated their perception of peripheral muscle fatigue. Visual analog scales (VAS) were used to rate different aspects of well-being. RESULTS: Both the perception of peripheral fatigue and the different VAS ratings had changed positively after training. Three patients achieved higher peak torque levels throughout the posttraining endurance test. CONCLUSION AND DISCUSSION: Based on these positive results, the authors conclude that more comprehensive studies of exercise prescription in patients with multiple sclerosis are desirable.

Activities of Daily Living↗
PubMed1994

The mean frequency of the EMG of the knee extensors is torque dependent both in the unfatigued and the fatigued states.

The present study aimed to investigate the shift in the mean frequency (fmean) of the power density spectrum of the electromyogram (EMG) during endurance tests of the knee extensors at three different torque levels (70% MVC, 25% MVC and 10% MVC). Fourteen clinically healthy men performed the three endurance tests until exhaustion. Surface EMG(s) were obtained from the vastus medialis, the vastus lateralis and the rectus femoris muscles and fmean and signal amplitude (RMS) were computed. The subjects rated the perception of fatigue in the knee extensor muscles throughout the three tests using a 10-point graded scale. The endurance time increased with decreasing torque level. A significantly higher perception of fatigue was found at the low torque level (10% MVC) at the end of the endurance time. Individual time series analysis (using linear regression) was performed. It was found that linear models described well the behaviour of fmean throughout the endurance time at the three torque levels. When the endurance times were normalized significant differences in the rate of decrease in fmean were found for vastus lateralis and rectus femoris; the rate decreased with decreasing torque level. For these two muscles significant differences were also found in fmean in the unfatigued state; at 10% MVC significantly lower fmean was found. The present study demonstrated both that the unfatigued fmean and the rate of decrease in fmean (with normalized endurance time) were torque dependent. The latter finding, combined with our result that the subjective fatigue was highest at the lowest torque level, calls into question the use of fmean as a valid indicator of peripheral fatigue.

Adult↗
PubMed1994

Factors interacting with perceived work-related complaints in the musculoskeletal system among home care service personnel. An explorative multivariate study.

The interrelationships between reported complaints, certain sociodemographic data and ergonomic, physical and psychosocial aspects of the work-environment were investigated in a cross-sectional study of home care service personnel using a questionnaire. Ninety-seven out of 160 randomly selected women took part in pre-tests (presented here), post-tests and one year exercise program. Significant correlations existed between musculoskeletal complaints, other (somatic and psychosomatic) symptoms and anxiety/threat for differently, mainly work-related negative changes. The group of subjects could be divided into three subgroups. A "complaint group" was identified with a high prevalence of musculoskeletal and other somatic/psychosomatic symptoms. This group had the most negative ratings on the ergonomic and physical work-environment indices. A "young group" had the most negative perception of the psychosocial work-environment. The "healthy group" generally perceived the situation best. The present preliminary study could indicate that work-related interventions/rehabilitation programmes undertaken for the complaint group must be designed in another way and with other goals than those directed towards the other two identified groups.

Adult↗