Biomedical subjects

I Bradl

Publications and source records attributed to I Bradl.

4 recordsLinked to original sources

PubMed2005

Improved evaluation of back muscle SEMG characteristics by modelling.

Surface EMG (SEMG) as non-invasive method is a valuable tool in functional studies of movement co-ordination. The interpolation of the SEMG power (EMG mapping) gives information about intra- and inter-muscular co-ordination. It has been shown that SEMG maps of low back pain patients and healthy subjects differ. The only major drawback to SEMG is that volume conduction of muscle tissue, fat, and skin decreases the spatial and temporal resolution of signals. To improve the interpretation of SEMG signals, we have applied high pass filtering of cross covariance functions, which has proved to be useful in increasing the spatial resolution, to SEMG data of the back region. Experimental data demonstrate that SEMG signals from the back extensors show only rarely signs of action potential propagation. This behaviour, also described in the literature, can be explained by a model assuming short, deep muscle fibres, having bipolar end effects, with overlapping positions parallel to the fibre direction. This condition is fulfilled by the mm. multifidii et rotatores which are part of the m. erector spinae. Although the model is simplistic, the agreement between simulations and experiments is good.

Journal Article↗

PubMed2005

Back muscle activation pattern and spectrum in defined load situations.

For the prevention and rehabilitation of low back pain the understanding muscle function in the low back region is essential. Important aspects of function include the muscle activation patterns and muscle fatigue. In the low back region m. erector spinae plays a critical role. The different parts of this muscle complex differ considerably in function. Following the concept of Bergmark [A. Bergmark, Stability of the lumbar spine, Acta Orthop. Scand. 60 (1989) 1-54] trunk muscles can be divided in two subsystems, the global-mobilizing-system and the local-stabilizing-system. At present the multifidus muscles are assigned to the local whereas the longissimus and iliocostalis muscles are assigned to the global system. From results of the four parts of our investigation, it can be shown that essential information about muscle function can be obtained by spectral and intra- as well as inter-muscular surface EMG parameters. Obtained data demonstrated functional transitions between the local and global system of trunk muscles for the multifidus muscle.

Journal Article↗

PubMed2002

[Contractile reserve as a new parameter for determining the performance of the heart muscle using a noninvasive measuring method].

Chronic cardiac insufficiency is an illness with increasing epidemiological importance and mortality. Therefore different invasive and non-invasive investigation methods for early recording were developed. The left ventricular ejection fraction (LVEF) has played a special role in this direction. The determination of the contractile reserve by means of non-invasive measurement of blood pressure and flow through the aortic valve is a new and up to now widely unknown method for recording the capability and power reserve of the of myocardium. Since no comparative investigations are known from literature and results from a follow-up are not available yet, we tested whether, by means of contractile reserve, the discrimination of subjects with different cardiac power is possible or not. Forty-two men between 44 and 62 years of age belonging to three groups with different cardiac power (persistence trained, healthy subjects and patients with CHD) were examined non-invasively. The main result of the study is that it is possible to distinguish between the three groups significantly by means of the contractile reserve. The largest value (15.25 W +/- 3.46 W) was found in the "persistence trained" group, followed by the "healthy subjects" (10.85 W +/- 4.19 W). The smallest values were from the "patients" group (7.88 W +/- 2.95 W). The differences between the mean values of the CHD "patients" and the "persistence trained" were significant (p < 0.001). Similar comparisons of the groups of "healthy subjects" and "trained persons" and "healthy subjects" and "patients", respectively, yield p values of p = 0.007 and p = 0.040. These differences are also significant. This study is a first investigation and description of the method. A validation only can be achieved by follow-up investigations.

Adult↗

PubMed1999

Surface EMG of shoulder and back muscles and posture analysis in secretaries typing at visual display units.

OBJECTIVE: A study was carried out to investigate temporal changes of activation of shoulder and back muscles in workers at visual display units by means of surface EMG. Moreover, postural parameters were recorded to distinguish fatigue-related from posture-related changes of the myoelectrical activity. METHODS: Nine healthy female office workers typed texts spoken from tape during three 1-h-long sessions. After the first and again after the second hour there was a break of 15 min. Sixteen-channel surface EMG was bipolarly recorded from the erector spinae, trapezius, deltoid and sternocleidomastoid muscles. Root mean square (RMS) and power spectrum median frequency of the EMG were calculated. Sitting posture was assessed using an eight-channel movement analysis system with ultrasound markers. The position of the seventh cervical spinous process and the left and the right acromion were analysed synchronously with the EMG characteristics using regression analysis. RESULTS: The normalised RMS of the left and right trapezius muscle increased, while the median frequency did not change. The increase of the normalised RMS was significantly lower when the linear influence of posture was excluded. On average, the distance between C7 and the left and right acromion decreased within each working an hour. C7 became lower on average by 5.5 mm within an hour, whereas the acromions became lower by only 1.7 mm (left) and 3.3 mm (right). CONCLUSION: The increase in trapezius muscle activity was partly related to a lifting of the shoulders to compensate a slight slumping of the back. Another part of the EMG activity increase has to be attributed to fatigue, to attention-related activity or to the combination of both. Therefore, training of the back muscles and a varied organisation of work might have a preventive effect with respect to musculoskeletal complaints in VDU workers.

Adult↗