Biomedical subjects

Pierre A Mathieu

Publications and source records attributed to Pierre A Mathieu.

5 recordsLinked to original sources

PubMed2006

Automated decomposition of intramuscular electromyographic signals.

We present a novel method for extracting and classifying motor unit action potentials (MUAPs) from one-channel electromyographic recordings. The extraction of MUAP templates is carried out using a symbolic representation of waveforms, a common technique in signature verification applications. The assignment of MUAPs to their specific trains is achieved by means of repeated template matching passes using pseudocorrelation, a new matched-filter-based similarity measure. Identified MUAPs are peeled off and the residual signal is analyzed using shortened templates to facilitate the resolution of superimpositions. The program was tested with simulated data and with experimental signals obtained using fine-wire electrodes in the biceps brachii during isometric contractions ranging from 5% to 30% of the maximum voluntary contraction. Analyzed signals were made of up to 14 MUAP trains. Most templates were extracted automatically, but complex signals sometimes required the adjustment of 2 parameters to account for all the MUAP trains present. Classification accuracy rates for simulations ranged from an average of 96.3% +/- 0.9% (4 trains) to 75.6% +/- 11.0% (12 trains). The classification portion of the program never required user intervention. Decomposition of most 10-s-long signals required less than 10 s using a conventional desktop computer, thus showing capabilities for real-time applications.

Action Potentials↗

PubMed2005

Differences in multi-joint kinematic patterns of repetitive hammering in healthy, fatigued and shoulder-injured individuals.

BACKGROUND: Work-related musculo-skeletal disorders have been previously related to movement repetition, inadequate postures, non-ergonomic environments, muscular imbalance and fatigue. However, no direct link between fatigue and injury has been experimentally shown. To address this problem, we compared the effects of fatigue and injury on the kinematics of repetitive hammering. METHODS: Healthy subjects (n=30) hammered repetitively both before and after fatigue. Fatigue was induced by a combination of static and dynamic procedures. Shoulder-injured subjects (n=15) hammered for 30s without fatigue. Kinematics of motion was recorded. FINDINGS: The movement time and shoulder range of motion during hammering were not affected by either fatigue or shoulder injury. When fatigued, the healthy subjects displayed decreased range of joint motion, peak velocity and peak acceleration of elbow motion during hammering as well as reduced grip strength. Shoulder-injured individuals had a smaller hammer trajectory amplitude than healthy controls with or without fatigue. They also had lower wrist range of motion, elbow peak velocity, and peak wrist and elbow acceleration compared to healthy subjects hammering without fatigue but only lower wrist peak acceleration compared to healthy subjects hammering with fatigue. INTERPRETATION: Results showed that fatigue affects elbow motion while shoulder injury affects both wrist and elbow motions during hammering. However, shoulder kinematics were not changed by either fatigue or shoulder injury. These changes at the wrist and elbow may reflect strategies used by individuals with shoulder injury to maintain constant movement duration and shoulder kinematics during movement.

Adult↗

PubMed2003

Electromyography of scoliotic patients treated with a brace.

When a brace is used to correct spinal deviation, patients may seek to ease the discomfort from the pressure exerted by the orthosis by actively recruiting specific trunk muscles. The effect of bracing on trunk electromyography (EMG) has been reported in only one study where a limited number of electrodes were placed mainly in the thoracic region. Our hypothesis was that a multi-electrode mapping of the activity of the thoracic, lumbar, and abdominal trunk muscles would provide a more representative picture of the muscular reaction in response to bracing. With a larger number of EMG measuring sites, the presence of any brace-induced trunk muscle activity should be detected. Therefore, EMG signals of 11 adolescent idiopathic scoliosis patients who had been undergoing Boston brace treatment for 0.7-3 years were collected during four isometric tasks to evaluate the response of trunk muscles in the minutes following the application of the brace. Twenty-two pairs of bipolar electrodes were used to measure the EMG signals of the main superficial trunk muscles during four isometric tasks. EMG signals of trunk muscles were compared in braced and unbraced conditions. Brace-induced increases in EMG activity were significant in 43% of the individual measurements and in three of the four tasks for the group mean values. Increases were greater in the lumbar area, especially on the convex side of the secondary (lumbar) curve. These results thus suggest that immediately following the application of the brace, significant muscular responses can be observed in some patients.

Abdominal Muscles↗

PubMed2003

Continuous curve registration as an intertrial gait variability reduction technique.

Timing in peak values shifts slightly between gait trials. When gait data are averaged, part of the standard deviation could be associated with this intertrial variability unless normalization is carried out beforehand. The objective of this study was to determine how continuous curve registration, an alignment technique, can reduce intersubject variability in gait data without altering the original curve characteristics. Gait data were obtained by means of a four-camera high-speed video system synchronized to a force plate. The data for 60 gait trials were collected from 20 young, healthy subjects. Curve registration was applied to hip angular displacement, net moment, and power curves generated in the sagittal plane. Following registration, the peak values increased by an average of 1.2% (0.11 +/- 0.26 degrees) for angular displacement, and by 11.2% (0.11 +/- 0.09 W/kg) for power, while there were no changes for moments. First and second derivatives of the unregistered and registered curves did not display significant differences, and the harmonics were barely affected. Continuous curve registration would thus be an appropriate technique for application prior to any statistical analysis using able-bodied gait patterns.

Adult↗

PubMed2002

Movement reorganization to compensate for fatigue during sawing.

Peripheral (muscle) aspects of fatigue are well documented. However, little is known about the central aspects of fatigue that could influence, in particular, multijoint coordination. To investigate the central aspects of fatigue, we compared the multijoint kinematics of non-fatigued and fatigued individuals while sawing. Muscle fatigue was associated with decreases in sawing force and movement amplitude at the elbow whereas the basic characteristics of the saw trajectory, including the movement direction, extent and duration, remained invariant. This invariance was maintained by increasing the movement amplitude at the wrist, shoulder and trunk. The system thus takes advantage of the redundancy of the motor apparatus to maintain the endpoint trajectory despite fatigue.

Adult↗