Journal of electromyography and kinesiology : official journal of the International Society of Electrophysiological Kinesiology
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J Electromyogr Kinesiol · Feb 2011
Introducing the reflex probability maps in the quantification of nociceptive withdrawal reflex receptive fields in humans.
The aim of the present study was to improve the assessment of reflex receptive fields (RRF) in humans, using reflex sensitivity and reflex probability maps. Repeated electrical stimulation was applied to elicit the nociceptive withdrawal reflex (NWR) in fifteen healthy volunteers using two stimulation paradigms: fixed (FSI) and adjusted (ASI) stimulation intensities. Stimulation was applied on sixteen sites in the foot sole, and pain intensity ratings and EMG responses were recorded. ⋯ In all cases, the estimation error remained under 10% and 5% after five and ten repetitions, respectively. The 2nd stimulus in the train consistently rendered larger and more reliable RRF areas than the 1st stimulus. The present analysis can be useful in order to identify the most adequate stimulation parameters and quantification variables for RRF assessment in experimental and clinical pain research.
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J Electromyogr Kinesiol · Aug 2010
The effect of increased physical load during an active straight leg raise in pain free subjects.
It has been proposed that pelvic girdle pain (PGP) subjects adopt a high load motor control strategy during the low load task of the active straight leg raise (ASLR). This study investigated this premise by observing the motor control patterns adopted by pain free subjects during a loaded ASLR (ASLR+PL). ⋯ Pain free subjects respond to an ASLR+PL by a general increase in anterior trunk muscle activation, but preserve the pattern of greater activation on the side of the leg lift observed during an unloaded ASLR. This contrasts to findings in PGP subjects who, despite having a high load strategy for performing an ASLR on the symptomatic side of the body, display equal bilateral activation of the anterior abdominal wall during the ASLR. This differentiates PGP subjects from pain free subjects, supporting the notion that PGP subjects have aberrant motor control patterns during an ASLR.
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J Electromyogr Kinesiol · Jun 2010
The role of anticipatory postural adjustments in compensatory control of posture: 1. Electromyographic analysis.
Anticipatory (APAs) and compensatory (CPAs) postural adjustments are the two principal mechanisms that the central nervous system uses to maintain equilibrium while standing. We studied the role of APAs in compensatory postural adjustments. Eight subjects were exposed to external predictable and unpredictable perturbations induced at the shoulder level, while standing with eyes open and closed. ⋯ When the perturbations were predictable, strong anticipatory activation was seen in all the muscles: such APAs were associated with significantly smaller compensatory activity of muscles and COP displacements after the perturbations. The outcome of the study highlights the importance of APAs in control of posture and points out the existence of a relationship between the anticipatory and the compensatory components of postural control. It also suggests a possibility to enhance balance control by improving the APAs responses during external perturbations.
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J Electromyogr Kinesiol · Jun 2010
A wavelet-based adaptive filter for removing ECG interference in EMGdi signals.
Diaphragmatic electromyogram (EMGdi) signals convey important information on respiratory diseases. In this paper, an adaptive filter for removing the electrocardiographic (ECG) interference in EMGdi signals based on wavelet theory is proposed. ⋯ Simulation results show that the power spectral density (PSD) of the extracted EMGdi signal from an ECG corrupted signal is within 1.92% average error relative to the original EMGdi signal. Testing on clinical EMGdi data confirm that this method is also efficient in removing ECG artifacts from the corrupted clinical EMGdi signal.
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J Electromyogr Kinesiol · Jun 2010
Adaptations of upper trapezius muscle activity during sustained contractions in women with fibromyalgia.
The study compared the distribution of electromyographic (EMG) signal amplitude in the upper trapezius muscle in 10 women with fibromyalgia and in 10 healthy women before and after experimentally-induced muscle pain. Surface EMG signals were recorded over the right upper trapezius muscle with a 10 x 5 grid of electrodes during 90 degrees shoulder abduction sustained for 60s. The control subjects repeated the abduction task following injections of isotonic and hypertonic (painful) saline into the upper trapezius muscle. ⋯ The patient group showed lower average EMG amplitude than the controls during the contraction (P<0.05) and did not show different changes in EMG amplitude between different regions of the upper trapezius. A similar behavior was observed for the control group following injection of hypertonic saline. The results indicate that muscle pain prevents the adaptation of upper trapezius activity during sustained contractions as observed in non-painful conditions, which may induce overuse of similar muscle compartments with fatigue.