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Biomedical subjects

B Gerdle

Publications and source records attributed to B Gerdle.

At least 37 records · Page 2Linked to original sources
PubMed2000

Criterion validation of surface EMG variables as fatigue indicators using peak torque: a study of repetitive maximum isokinetic knee extensions.

A number of studies have been published that have used variables of the electromyogram (EMG) power spectrum during dynamic exercise. Despite these studies there is a shortage of studies of the validity of surface EMG registrations during repetitive dynamic contractions with respect to fatigue. The aim of this study was to investigate if the surface EMG variables mean frequency (MNF [Hz]) and the signal amplitude (RMS [microV]) are valid indicators of muscular fatigue (defined as "any exercise-induced reduction in the capacity to generate force or power output") during maximum repeated isokinetic knee extensions (i.e. criterion validity using peak torque). Twenty-one healthy volunteers performed 100 isokinetic knee extensions at 90 degrees s(-1). EMG signals were recorded from the vastus lateralis, the rectus femoris and the vastus medialis of the right thigh by surface electrodes. MNF and RMS of the EMG together with peak torque (PT [Nm]) were determined for each contraction. MNF showed consequently higher correlation coefficients with PT than RMS did. Positive correlations generally existed between MNF and PT. The majority of the subjects had positive correlations between RMS and PT (i.e. decreases both in PT and in RMS). In conclusion, at the individual level MNF generally - in contrast to RMS - showed good criterion validity with respect to biomechanical fatigue during dynamic maximum contractions.

Adult↗
PubMed2000

Intramuscular pressure and electromyographic responses of the vastus lateralis muscle during repeated maximal isokinetic knee extensions.

The purpose of the study was to investigate changes in intramuscular pressure (IMP) (maximal during contraction - peak IMP, and between contraction, relaxation IMP - RxIMP) and surface electromyographic activity (EMG) parameters [mean frequency of the power spectrum (fmean), and signal amplitude, root mean square (RMS)] throughout 100 repetitive isokinetic contractions for six healthy subjects. Parameters were recorded simultaneously from the vastus lateralis muscle during maximal knee extension. Regression analyses revealed significant decreases for peak IMP and fmean, and an increase in RxIMP; RMS, however, did not change. All parameters demonstrated trends of change throughout the contractions that were non-linear. Details and inter relations for RxIMP and fmean were highlighted to express intramuscular fluid accumulation and fatigue development, respectively. Individual regression analyses for RxIMP revealed significant positive correlations for all subjects (range of r=0.62 to 0.89). At group level, mean RxIMP increased from 6.0 mmHg for the 1st contraction to 14.0 mmHg for the 100th contraction. For fmean, individual regressions were significantly negative for all subjects (r=-0.75 to -0.89). Fmean decreased from 89.2 Hz for the 1st contraction to 63.3 Hz for the 100th contraction. When the data were delineated between the fatigue (contractions 1-40) and endurance phases (41-100), the slopes of increase for RxIMP, and of decrease for fmean were significantly greater during the fatigue phase. RxIMP throughout the 100 contractions correlated negatively with fmean for each subject (r=-0.54 to -0.78); when delineated, the correlation between parameters was significantly greater for the fatigue as compared with the endurance phase. Relaxation IMP trends are mainly attributed to intramuscular water accumulations during repetitive contractions. In spite of consistent correlations between RxIMP and fmean a causal association could not be established. It may be suggested that a common factor occurring during the fatiguing process governs changes in RxIMP and fmean.

Adult↗
PubMed2000

Correlations between joint and spinal mobility, spinal sagittal configuration, segmental mobility, segmental pain, symptoms and disabilities in female homecare personnel.

The aim of a study comprising 607 women working as homecare personnel was to investigate general spinal, joint and segmental mobility, different symptoms (pain and strain) and their relation to various aspects of disability. Joint mobility (mainly peripheral) was estimated using the "Beighton" score and spinal posture and mobility were measured by kyphometer. Passive segmental mobility and pain provocation were estimated manually. Pain intensity and strain during work and leisure were estimated using visual analogue scales for defined anatomical regions. Disability was rated using defined items and two indices. The 7-day prevalence of low back pain was 48%. Peripheral joint mobility, spinal sagittal posture and thoracic sagittal mobility showed low correlations with disability. Lumbar sagittal hypomobility was associated with higher disability. Manually estimated segmental mobility and segmental pain provocation of L4-L5 and L5-S1 correlated with disability; hypo- and hypermobility or positive pain provocation tests at these levels showed higher disability than normal mobility and negative pain provocation tests, respectively. Cluster analysis revealed that the combination of positive pain provocation tests and low lumbar sagittal mobility was associated with particularly high disability levels. In conclusion, positive pain provocation tests were clearly associated with high disability levels.

Activities of Daily Living↗
PubMed1999

Reproducibility of surface EMG variables and peak torque during three sets of ten dynamic contractions.

The interpretation of the electromyogram (EMG) of dynamic contractions might be difficult because the movement per se introduces additional factors that could affect its characteristics. There is a lack of studies concerning the reproducibility of surface EMG registrations during dynamic contractions. The aim was to investigate the during-the-day reproducibility (using intra-class correlation; ICC) of the peak torque (PT) and the EMG variables (without removing the electrodes) of dynamic contractions. Ten healthy subjects performed three sets of 10 dynamic maximum right-knee extensions with a one-hour interval in between, using an isokinetic dynamometer and the PT was determined. EMG signals were recorded from the right vastus lateralis, rectus femoris and vastus medialis muscles 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 in-between the maximum extensions was calculated as a ratio of the RMS during the passive flexion phase and the RMS during the active extension phase of each contraction cycle: the signal amplitude ratio (SAR). Both PT (ICC = 0.99) and RMS (ICC = 0.83-0.98) had good reproducibility. The reproducibility of MNF was good for all muscles when the mean of contraction nos.: 1-10 was used. Vastus lateralis had the highest ICC among the three muscles. The reproducibility of SAR was generally poor (ICC < 0.60). The present study showed good reproducibility for common EMG variables (MNF and RMS) obtained during maximum isokinetic contractions.

Adult↗
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↗
PubMed1997

Neuropsychological aspects of driving after brain lesion: simulator study and on-road driving.

Twenty-nine patients with brain lesion and 29 matched controls participated in the study. The patients were socially well recovered with a high rate of employment. Compared with the controls, they performed significantly worse on a neuropsychological test battery, especially on executive and cognitive functions. Patients drove as well as controls in predictable situations in the advanced simulator used. In unpredictable situations, they demonstrated longer reaction times and safety margins, as well as difficulties in allocating processing resources to a secondary task. The patients showed significantly less attention, worse traffic behavior, and less risk awareness when driving in real traffic. Forty-one percent of the patients did not pass the driving test. The neuropsychological test battery was factor analyzed into four factors: executive capacity, cognitive capacity, automatic attentional capacity, and simple perceptual-motor capacity. The second factor was the mast significant with a simultaneous capacity test predicting driving performance with 78% confidence.

Journal Article↗