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Biomedical subjects

J Duchêne

Publications and source records attributed to J Duchêne.

8 recordsLinked to original sources
PubMed1996

Surface electromyography as a tool to study the head rest comfort in cars.

In this study, two methods were presented in order to evaluate objectively the comfort of head rests in cars using surface electromyography (SEMG). First, the Amplitude Probability Density Function (APDF) was computed. Extremely low level intensity activities were measured. No significant differences were observed on SEMG global activity between experiments with and without a head rest. Second, instead of computing one APDF, several APDF were calculated over time. Analyses focused on the rate of evolution of APDF parameters. This was a time varying APDF (TAPDF). This last method allowed a better diagnosis than the first one. For drivers, significant decreases in SEMG activity were observed when using a head rest. For passengers, a contradictory increase in SEMG activity was observed during experiments with a head rest. This observation was explained by the seat back angle chosen by passengers.

Arousal↗
PubMed1993

MicroPACS: a PC-based small PACS implementation.

To make picture archiving and communication systems (PACS) a practical reality for small-scale structures, it appears necessary to build a network that integrates and optimises production management, analysis and storage of images, and to include the ability to communicate with other similar remote structures. To solve the various technical problems related to small-scale PACS implementation, MicroPACS, a local area network, was developed around PC-like microcomputers. Every necessary function is assessed and implemented, including a centralised data-base, a distributed image bank, different storage levels and a specific task for image exchanges. An additional protocol was also developed for remote consultation through ISDN. Standardisation of image encapsulation and a point-to-point link between remote sites ensure easy transfers between heterogeneous local networks or bases and integrity of local databases.

Computer Communication Networks↗
PubMed1993

Uterine electromyography: a critical review.

On the basis of a literature review, this work summarizes uterine animal and human electromyographic information obtained at cellular, myometrial, and abdominal levels during gestation and parturition. We show that both internal and external electromyograms occur in phase with intrauterine pressure increase and exhibit similar spectra, including a slow wave (0.01 < frequency < 0.03 Hz) probably because of mechanical artifacts and a fast wave whose frequency content can be subdivided into a low-frequency band always present in every contraction and a high-frequency band related to efficient parturition contractions. Application of classic spectral techniques to electromyogram envelopes has identified group propagation but not pacemaker areas. However, no time delay or classic propagation has been demonstrated by applying the same spectral techniques to the electromyogram itself, probably because of the nonlinearity and three-dimensional nature of the propagating process.

Animals↗
PubMed1993

Surface electromyogram during voluntary contraction: processing tools and relation to physiological events.

Surface electromyography (SEMG) has been used extensively in the last years in a variety of applications, including muscle function assessment, pathology identification, ergonomics, pattern analysis, or population characterization. Advanced processing methods, especially in the spectral domain, provide the research worker with more and more precise and user-friendly tools for signal characterization, analysis, and classification. The use of such sophisticated tools requires many assumptions on signal characteristics, and the wide variety of computing options related to each processing method makes it difficult to compare the results of different works when these options are omitted in the reports or improperly applied. This work first aims at taking stock of the various processing methods which have emerged in the last years around surface electromyography: signal acquisition, random feature extraction, time and spectral parameter determination, statistical tests application. The main methods are briefly explained and discussed, then variations between apparently equivalent methods are pointed out, necessary hypotheses are underlined, and the use of such methods in SEMG processing is shown with respect to the more recent works. A second section shows how authors deal with parameters extracted from SEMG in order to relate them to physiological modifications (force, fiber type, fiber environment).

Adult↗
PubMed1990

Electromyogram power spectrum during dynamic contractions at different intensities of exercise.

During dynamic contractions performed on a cycle ergometer, we studied the influence of motor unit (MU) recruitment on the electromyographic (EMG) spectral content by exerting mechanical power of different intensities, which was chosen to remain below the maximal aerobic power (VO2max). The spectral parameters: EMG total power (PEMG), mean (MPF) and median (MED) power frequencies, which are the most representative of the EMG spectral content, were calculated according to the EMG activity of the vastus medialis muscle (VM) and soleus muscle (SOL) of the right leg. For VM and SOL, PEMG increased linearly with exerted power demonstrating an enhancement of MU recruitment. Moreover these relationships were less scattered when exerted power was expressed as a percentage of VO2max. Changes in MPF and MED with varying exercise intensities were different from one subject to another. For a set of subjects, MPF and MED were found to be independent of exerted power. Although VM and SOL muscles are different in fibre type composition, similar results were obtained for both EMG activities. We have concluded that for dynamic contractions performed at different intensities below VO2max, the recruitment of the MU has a poor effect on the EMG spectral content whatever the predominant type of fibre.

Adult↗
PubMed1990

EMG spectral shift as an indicator of fatigability in an heterogeneous muscle group.

Changes in electromyogram (EMG) power spectra were investigated in the triceps surae muscles of two classes of individuals (untrained subjects and athletes) maintaining a plantarflexion torque of 80% of maximal voluntary contraction until exhaustion. A set of 23 parameters describing changes in the frequency content and power of EMG was defined. For most experiments, classical changes were found, indicating a shift of the EMG spectra towards lower frequencies and an increase in the total power of the signals. In 12% of the experiments, alternations in activity between synergistic muscles were found, leading to a large variability in the spectral parameters. After the expression of each experiment in terms of a reduced data matrix and matrix to vector transformations, three methods of discrimination were used to classify subjects with respect to changes in the EMG signal during sustained contraction: (1) evaluation of the most discriminating parameter, (2) principal components analysis, (3) transformation maximizing differences between classes. Method (3) was found to be preferable since it led to good separation of the two classes in a reference group of subjects and a satisfactory projection of each individual from a group of unknowns into the appropriate class. These results suggest using a method such as this for ergonomic or athletic training purposes rather than the usual method of monitoring the frequency shift of the EMG.

Adult↗