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Biomedical subjects

Thomas Läubli

Publications and source records attributed to Thomas Läubli.

9 recordsLinked to original sources
PubMed2006

Magnetic resonance imaging of the lumbar spine: findings in female subjects from administrative and nursing professions.

STUDY DESIGN: Cross-sectional magnetic resonance imaging (MRI) study. OBJECTIVE: To find out whether different patterns of lumbar disc degeneration related to different physical work types (static vs. dynamic) can be found. SUMMARY OF BACKGROUND DATA: The association of lumbar disc degeneration with physical workload as well as the association of disc degeneration with low back pain (LBP) has been debated controversially. Nevertheless, many of the mainly invasive treatment concepts are based on disc degeneration models. METHODS: An MRI study was performed in female subjects aged 45 to 62 years with persistent LBP and in age-matched controls. Subjects (n = 109) were selected from nursing and administrative professions. A questionnaire was used to assess the subjects' exposure to physical workplace factors. Disc degeneration, disc herniation, nerve root compromise, high intensity zones, endplate changes, and facet joint osteoarthritis were evaluated based on sagittal T1- and T2-weighted as well as axial T2-weighted images. RESULTS: The two occupational groups could clearly be distinguished by the physical workplace factors: administrative work was associated with predominantly sitting postures whereas nursing work was associated with frequent walking, pushing, pulling, and lifting. Except for endplate (Modic) changes at L5-S1, MRI findings did not differ between the four groups, namely, nurses and secretaries with and without LBP. When analyzing the MRI findings within the two vocational groups, nerve root compromise and endplate changes in the lower lumbar spine were found to be significant (P < 0.05) risk factors for LBP. Disc degeneration, disc herniation, nerve root compromise, and facet joint osteoarthritis were present in more than 50% of the intervertebral spaces studied. CONCLUSIONS: These findings give evidence that in subjects performing nonheavy work, patterns of lumbar disc degeneration are not associated with the job type and characteristic physical loadings.

Cross-Sectional Studies↗
PubMed2005

Long-term effects of supervised physical training in secondary prevention of low back pain.

BACKGROUND AND OBJECTIVES: In the last few years, several studies have focused on short-term treatment effects of exercise therapy. However, there is a lack of knowledge concerning the long-term treatment effects recorded after several years. Hence, this study was performed to investigate the short- and long-term effects of supervised physical training on functional ability, self-rated pain and disability in secondary prevention of low back pain. METHODS: One hundred and eighty-three hospital employees with chronic low back pain were randomly assigned either to back school (comparison group), or three-months supervised physical training including a back school (exercise group). Various measurements of functional ability were performed and subjects completed questionnaires on self-rated pain, disability, and general well-being before treatment, immediately after intervention, and at six-months follow-up. At one-year and at ten-years follow-up participants evaluated treatment effectiveness. RESULTS: Out of 183 employees, 148 completed the program. Participation at follow-ups ranged from 66 to 96%. Supervised physical training significantly improved muscular endurance and isokinetic strength during a six-months follow-up, and effectively decreased self-rated pain and disability during a one-year follow-up. At ten-years follow-up the subjects' assessment of the effectiveness of treatment was significantly better in the exercise group. CONCLUSIONS: Supervised physical training effectively improved functional capacity and decreased LBP and disability up to one-year follow-up. The subjects' positive evaluation of the treatment effect at ten-years follow-up suggests a long-term benefit of training.

Adult↗
PubMed2004

Single motor unit and spectral surface EMG analysis during low-force, sustained contractions of the upper trapezius muscle.

Intramuscular and surface electromyographic (EMG) activities were recorded from the left and right upper trapezius muscle of eight healthy male subjects during 5-min long static contractions at 2% and 5% of the maximal voluntary contraction (MVC) force. Intramuscular signals were detected by wire electrodes while surface EMG signals were recorded with linear adhesive electrode arrays. The surface EMG signals were averaged using the potentials extracted from the intramuscular EMG decomposition as triggers. The conduction velocity of single motor units (MUs) was estimated over time from the averaged surface potentials while average rectified value and mean power spectral frequency were computed over time from 0.5 s epochs of surface EMG signal. It was found that (1) MUs were progressively recruited after the beginning of sustained contractions of the upper trapezius muscle at 2% and 5% MVC, (2) the conduction velocity of the MUs active since the beginning of the contraction significantly decreased over time, and (3) although the CV of single MUs significantly decreased, the mean power spectral frequency of the surface EMG did not show a consistent trend over time. It was concluded that spectral surface EMG analysis, being affected by many physiological mechanisms, may show limitations for the objective assessment of localized muscle fatigue during low force, sustained contractions. On the contrary, single motor unit conduction velocity may provide an early indication of changes in muscle fiber membrane properties with sustained activity.

Action Potentials↗
PubMed2004

Trapezius muscle motor unit activity in symptomatic participants during finger tapping using properly and improperly adjusted desks.

Work-related musculoskeletal disorders in the neck-shoulder area and upper extremities are common among computer users, especially women. We compared temporal changes of motor unit (MU) activation in the trapezius muscle during finger tapping using both appropriate and inappropriate ergonomic desk adjustments. Sixteen intensive and nonintensive computer users with either moderate or severe musculoskeletal disorders participated in the study. Six-channel intramuscular electromyographic (EMG) signals and 2-channel surface EMG were recorded from 2 positions of the trapezius muscle. A statistically significant increase in activity was observed with a desk adjusted 5 cm higher than appropriate and was attributable mainly to increased duration of MU activity. Participants with severe symptoms activated more MUs, and these were also active longer. In women, on average, MUs were active nearly twice as long as in men during the same tapping task. This study demonstrates that it is possible to evaluate ergonomic topics on the MU level and that incorrectly adjusted office equipment, in addition to motor demands imposed by the work task, results in prolonged activity of MUs. A potential application of this research is an increased awareness that certain individuals who work with incorrectly adjusted office equipment may be at greater risk of developing work-related musculoskeletal disorders.

Biomechanical Phenomena↗
PubMed2003

Motor unit identification in two neighboring recording positions of the human trapezius muscle during prolonged computer work.

Work-related shoulder-neck pain is a major health risk in computer operators. To understand the physiological mechanisms behind the development of these disorders, EMG recordings of some minutes up to several hours must be accurately decomposed. For this reason we developed EMG-LODEC, an automatic decomposition software program, especially designed for multi-channel long-term recordings of signals detected during slight muscle movements. The subjects executed a 30-min computer task to simulate real work conditions while working at an ergonomically designed workstation. Six-channel intramuscular EMG signals were recorded from two positions of the upper trapezius muscle. The EMG signals were decomposed into individual motor unit action potential trains using EMG-LODEC. The study design enabled us first to study the dependence of intramuscular analysis on the insertion points and second to test the accuracy of the decomposition technique under laboratory conditions during a real experiment. The two positions yielded 887 motor units--452 located in position 1 and 435 in position 2. Although the numbers of detected action potentials were strongly correlated between the two insertion positions, different motor units were mostly recorded. In particular, the detection of continuously active motor units is specific for the selected insertion points and may not be representative of a muscle, not even for parts with common functions. The approach for the quantitative evaluation of the decomposition technique was to independently decompose two signals that were simultaneously detected by separate sets of wire electrodes placed close to each other in the muscle. Common trains discovered in each signal were compared for consistency. A cross-correlation analysis was performed to find corresponding motor unit pairs that were concurrently active. Concurrently active motor units were found in six subjects. For these motor units the extent of simultaneous occurrence of motor unit action potentials between the two positions ranged from 23% to 78% depending on the distinction of the single motor units and the number of superimposed motor unit action potentials. High concordance was seen in 3 out of the 15 motor unit pairs. Based on the results, EMG-LODEC is capable of providing reliable decompositions with satisfying accuracy and reasonable processing time. EMG-LODEC is suitable for the study of motor unit discharge patterns and recruitment order in subjects with and without musculoskeletal pain during long-term measurements to study work-related musculoskeletal disorders.

Adult↗
PubMed2003

A software package for the decomposition of long-term multichannel EMG signals using wavelet coefficients.

This paper presents a method to decompose multichannel long-term intramuscular electromyogram (EMG) signals. In contrast to existing decomposition methods which only support short registration periods or single-channel recordings of signals of constant muscle effort, the decomposition software EMG-LODEC (ElectroMyoGram LOng-term DEComposition) is especially designed for multichannel long-term recordings of signals of slight muscle movements. A wavelet-based, hierarchical cluster analysis algorithm estimates the number of classes [motor units (MUs)], distinguishes single MUAPs from superpositions, and sets up the shape of the template for each class. Using three channels and a weighted averaging method to track action potential (AP) shape changes improve the analysis. In the last step, nonclassified segments, i.e., segments containing superimposed APs, are decomposed into their units using class-mean signals. Based on experiments on simulated and long-term recorded EMG signals, our software is capable of providing reliable decompositions with satisfying accuracy. EMG-LODEC is suitable for the study of MU discharge patterns and recruitment order in healthy subjects and patients during long-term measurements.

Action Potentials↗
PubMed2002

Measures of low back function: a review of reproducibility studies.

OBJECTIVE: The objective of the present study was to make a systematic literature review with preset quality criteria concerning reproducibility of the tests of the low back regarding strength, endurance and range of motion. DESIGN: Literature in Medline and local databases was reviewed for articles concerning the reproducibility of strength, endurance, and range of motion measurements. BACKGROUND: Measures of low back function are widely used, and are important for both clinical and research purposes in relation to low back problems. A review of the reproducibility of these tests has not previously been made. METHODS: After extensive discussion among all the authors, general evaluation parameters were defined for the quality assessment. Every study was graded from 0 to 2 for each parameter. Parameters evaluated were: number of subjects, subject description, method description, test/retest interval, description of results, and statistics. RESULTS: The literature search revealed a total of 79 studies. Most studies suffered from methodological weaknesses and only eleven studies received ten or more quality points (maximum 14). The results from the highest graded studies are highlighted. CONCLUSIONS: It may be concluded that there is a considerable lack of information about the reproducibility of functional measures for the low back, and therefore a recommendation for consensus is difficult. However, most tests performed in the sagittal plane are reliable for use on groups. RELEVANCE: Measures of low back function are thought to be of great importance for clinicians, and low back researchers in general. A review of reproducibility will be helpful both as a survey of tests, and to provide information on the usefulness in relation to the level of reproducibility.

Biomechanical Phenomena↗