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  • 1
    Digitale Medien
    Digitale Medien
    The influences of muscle fibre proportions and areas upon EMG during maximal dynamic knee extensions (2000)
    Springer
    European journal of applied physiology 81 (2000), S. 2-10 
    Details
    ISSN: 1439-6327
    Schlagwort(e): Key words Dynamic ; EMG ; Enzyme histochemistry ; Knee extensors ; Morphology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract This study is an investigation of the relationship between muscle morphology and surface electromyographic (EMG) parameters [mean frequency of the power spectrum (MNF), signal amplitude (root mean square, RMS) and the signal amplitude ratio (SAR; i.e. the ratio between the RMS level during the passive part of the contraction cycle and the RMS level during the active part of the contraction cycle)] during 100 maximal dynamic knee extensions at 90° · s−1. Each contraction cycle comprised of 1 s of active knee extension and 1 s of passive knee flexion. The surface EMG was recorded from the vastus lateralis muscle. Twenty clinically healthy subjects participated in the study, and muscle biopsy samples of the vastus lateralis were obtained from 19 of those subjects. The relationships between muscle morphology and EMG were investigated at three stages of the test: initially, during the fatigue phase (initial 40 contractions), and at the endurance level (the final 50 contractions). Major findings on correlations are that SAR and MNF tended to correlate positively with the proportion of type 1 fibres, and RMS correlated positively with the proportion of type 2 muscle fibres. The muscle fibre areas showed little correlation with the EMG variables under investigation. The results of the present study showed that the three EMG variables of a dynamic endurance test that were investigated (RMS, MNF and SAR) were clearly correlated with the proportions of the different fibre types, but only to a small extent with fibre areas. These findings contradict some of the theoretical models of the EMG, especially for parameters in the frequency domain.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/PL00013792
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  • 2
    Digitale Medien
    Digitale Medien
    Worsening of neck and shoulder complaints in humans are correlated with frequency parameters of electromyogram recorded 1-year earlier (1998)
    Springer
    European journal of applied physiology 79 (1998), S. 7-16 
    Details
    ISSN: 1439-6327
    Schlagwort(e): Key words Electromyogram ; Mean frequency ; Neck and shoulder problems ; Prospective study ; Signal amplitude ratio
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract 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° · 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 f mean 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 f mean was correlated with whether improvement or worsening occurred for complaints in the neck and or shoulders; a significant relationship (r 2 = 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 f mean variables and perception of fatigue were also of significance. The present study would indicate that a high degree of f mean shift correlates with improvement in neck and shoulder complaints 1 year later. One possible reason could be that f mean reflects the muscle morphology and/or a pathological situation for the type-1 muscle fibres.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004210050466
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  • 3
    Digitale Medien
    Digitale Medien
    Lack of gender differences in the ability to relax between repetitive maximum isokinetic shoulder forward flexions: a population-based study among northern Swedes (2000)
    Springer
    European journal of applied physiology 83 (2000), S. 246-256 
    Details
    ISSN: 1439-6327
    Schlagwort(e): Key words Electromyography ; Endurance ; Muscle ; Gender ; Strength
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The aim of the present study was to analyse the effects of gender and age in a population-based sample of clinically healthy subjects on: (1) strength, endurance and perception of fatigue, (2) mean frequency (MNF) of the electromyogram (EMG), and (3) the ability to relax between active contractions (signal amplitude ratio; SAR) of the surface EMG of an isokinetic shoulder forward flexion test. With this aim we have analysed aspects of the validity of MNF as an indicator of fatigue, using peak torque as a criterion variable. The subjects were 27 men and 28 women (age range: 20–60 years), who were obtained by random sample from the official census lists (participation rate: 66%). The peak torque and surface EMG of two portions of the trapezius, deltoid and infraspinatus muscles were recorded throughout 100 repetitive maximal isokinetic shoulder forward flexions. No significant differences in the perception of fatigue and relative endurance levels of peak torque and work were found between males and females. Males were significantly stronger than females and, on average, females produced approximately 60% of the output of the males; 76% after normalisation for body mass. The men had significantly lower MNF endurance levels for three of the investigated muscles. When controlled for age and body mass, the men had a significantly higher MNF of the deltoid muscle than did the females. These differences were only found for the deltoid muscle. Significant correlations existed between the MNF of the four muscles and biomechanical output, indicating criterion validity for the MNF variable with respect to fatigue. There were no significant effects of gender or age on the ability to relax between repetitive contractions (SAR). The higher prevalence of musculoskeletal complaints of the neck-shoulder region in females cannot be explained by a higher intrinsic muscle tension. Age, gender, body mass index and biomechanical output can have significant effects upon MNF. These effects are important considerations in the interpretation of MNF, for instance in ergonomic situations.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004210000300
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  • 4
    Digitale Medien
    Digitale Medien
    Muscular fatigue during repeated isokinetic shoulder forward flexions in young females (1989)
    Springer
    European journal of applied physiology 58 (1989), S. 666-673 
    Details
    ISSN: 1439-6327
    Schlagwort(e): Electromyography ; Fatigue ; Human ; Isokinetic ; Muscle ; Shoulder flexion
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Peak torque, work, mean power and electromyographic (EMG) activity were recorded for each of 150 repeated isokinetic maximal shoulder flexions (45°–90°) in 23 healthy females. From the EMG signals of trapezius, deltoid, infraspinatus and biceps brachii the mean power frequency and the signal amplitude were determined in real time. The mechanical output showed a steep decrease during the first 40 contractions, followed by a plateau maintained until the end. In all muscles, except the biceps brachii, significant decreases in mean power frequency occurred during the first 40 contractions, showing a tendency to stabilize around the same absolute frequency value. Signal amplitude increased in the trapezius, the deltoid and the infraspinatus, but was constant in the biceps brachii. For some individuals rather high EMG activity was recorded in the muscles during the time the arm was supposed to be passively extended to the starting position, and this was found to be associated with lower strength and endurance levels. Longitudinal analyses showed that the mean power frequencies correlated better than the signal amplitudes with the three mechanical variables. The results suggest that the initial steep decrease in mechanical performance and mean power frequency is caused by fatiguing of type 2 motor units.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00418515
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  • 5
    Digitale Medien
    Digitale Medien
    The relationship between contraction and relaxation during fatiguing isokinetic shoulder flexions. An electromyographic study (1989)
    Springer
    European journal of applied physiology 59 (1989), S. 303-309 
    Details
    ISSN: 1439-6327
    Schlagwort(e): Electromyography ; Fatigue ; Female ; Human ; Muscle
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Knowledge of the strength, endurance and coordination of the shoulder muscles during dynamic contractions in healthy women would contribute to the understanding of symptoms in that part of the body in patients with myalgia. Twenty clinically healthy women performed single maximal forward shoulder flexions at four different angular velocities (0.57–3.14 rad·s−1). The same subjects also took part in two endurance tests (at angular velocities of 0.57 and 2.09 rad·s−1, respectively) consisting of 150 repeated maximal shoulder flexions. Electromyographic activity (EMG) was registered from four shoulder flexors using surface electrodes. Work was used as the mechanical variable. During the endurance tests subjects rated their perception of fatigue in the shoulder muscles. Work and the amplitude of the EMG signals decreased with angular velocity. The mean power frequency of the EMG was constant in the span of angular velocities investigated. During the endurance tests, work and the mean power frequency decreased during the initial 40–60 contractions followed by stable levels. The relative work level was higher at 2.09 than at 0.57 rad·s−1. Greater relative increases of the signal amplitudes of EMG occurred at 2.09 than at 0.57 rad·s−1. The EMG activity between the flexions (during the supposed passive extension) was higher at 2.09 than at 0.57 rad·s−1. Such a high activity was associated with a low mechanical performance at 2.09 rad·s−1. It is suggested that the initial sharp decreases in work and in mean power frequency reflect the fatiguing of the fast twitch motor units. Dynamic work consisting of continuous activity could predispose to muscle complaints.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02388333
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  • 6
    Digitale Medien
    Digitale Medien
    Effect of a general fitness program on musculoskeletal symptoms, clinical status, physiological capacity, and perceived work environment among home care service personnel (1995)
    Springer
    The journal of occupational rehabilitation 5 (1995), S. 1-16 
    Details
    ISSN: 1573-3688
    Schlagwort(e): exercise ; home care ; musculoskeletal ; pain ; women ; work-related
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The aim of the present controlled study was to evaluate the effect of a general fitness program, performed by an occupational health service, using pre-post assessment for a number of different outcome measures. A total of 160 employees working in the central home care service district of Umeå, Sweden were asked to participate in a program of a 1-year long exercise program. Of the 160 selected, 54 subjects declined to participate and nine subjects were rejected after a medical check up. The remaining 97 subjects participated in a schedule consisting of pre-post medical and physiotherapy examinations, questionnaires concerning sociodemography, musculoskeletal and general health complaints and work environment, physiological tests of cardiovascular fitness, and of strength and endurance of shoulder flexors and knee extensors, and registration of sick leave. The subjects were randomly assigned to an exercise (treatment) or control group. The exercise group trained twice a week for 1 year using a mixed program including exercises for coordination, strength/endurance, and fitness. The test schedule was repeated for both groups after 1 year. The exercise intervention was associated with positive changes in prevalence and intensity of musculoskeletal and psychosomatic complaints, better physiotherapy status (less muscle tightness, better neck mobility, and less tender points), increased shoulder strength and increased coordination in thigh muscles. However, the exercise group reported worse situations post-exercise concerning aspects of their physical and psychosocial work-environment (i.e., concerning ergonomy, influence, appreciation and communication with work manager), which might have been due to stress associated with the exercise situation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02117816
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  • 7
    Digitale Medien
    Digitale Medien
    Randomized Controlled Trial of Physiotherapy and Feldenkrais Interventions in Female Workers with Neck-Shoulder Complaints (1999)
    Springer
    The journal of occupational rehabilitation 9 (1999), S. 179-194 
    Details
    ISSN: 1573-3688
    Schlagwort(e): Feldenkrais ; intervention ; musculoskeletal ; neck ; pain ; physiotherapy ; rehabilitation ; shoulders ; women ; work-related
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The present study aimed to investigate whether physiotherapy or Feldenkrais interventions resulted in a reduction of complaints from the neck and shoulders (prevalence, pain intensity, sick leave, and disability in leisure and work roles) in 97 female industrial workers (not on long-term sick leave). Range of motion of neck and shoulders, VO2, endurance score (i.e., summation of pain intensity ratings during a static shoulder flexion), cortical control according to the Feldenkrais methodology, and physiological capacity according to a dynamic endurance test of the shoulder flexors with simultaneous surface EMG were also recorded. The workers were randomized to: (1) physiotherapy group (PT-group; treatment according to the ergonomic program of the PTs of the occupational health care service), (2) Feldenkrais group (F-group; education according to the Feldenkrais methodology), or (3) control group (C-group; no intervention). Pre- and post-tests were made at one-year intervals. The two interventions lasted 16 weeks during paid working time. The F-group showed significant decreases in complaints from neck and shoulders and in disability during leisure time. The two other groups showed no change (PT-group) or worsening of complaints (C-group). The present study showed significant positive changes in complaints after the Feldenkrais intervention but not after the physiotherapy intervention. Possible mechanisms behind the effects in the F-group are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1021301801292
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