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

2004 ◽  
Vol 96 (2) ◽  
pp. 157-164 ◽  
Author(s):  
Dario Farina ◽  
Daniel Zennaro ◽  
Marco Pozzo ◽  
Roberto Merletti ◽  
Thomas Läubli
Keyword(s):  
Motor Unit ◽  
Trapezius Muscle ◽  
Surface Emg ◽  
Single Motor Unit ◽  
Single Motor ◽  
Upper Trapezius ◽  
Upper Trapezius Muscle

Rectification is required to extract oscillatory envelope modulation from surface electromyographic signals

2014 ◽  
Vol 112 (7) ◽  
pp. 1685-1691 ◽  
Author(s):  
Christopher J. Dakin ◽  
Brian H. Dalton ◽  
Billy L. Luu ◽  
Jean-Sébastien Blouin
Keyword(s):  
Motor Unit ◽  
Stimulus Frequency ◽  
Motor Units ◽  
Surface Emg ◽  
Medial Gastrocnemius ◽  
Single Motor Unit ◽  
Single Motor ◽  
Single Motor Units ◽  
Emg Signal ◽  
Envelope Modulation

Rectification of surface electromyographic (EMG) recordings prior to their correlation with other signals is a widely used form of preprocessing. Recently this practice has come into question, elevating the subject of EMG rectification to a topic of much debate. Proponents for rectifying suggest it accentuates the EMG spike timing information, whereas opponents indicate it is unnecessary and its nonlinear distortion of data is potentially destructive. Here we examine the necessity of rectification on the extraction of muscle responses, but for the first time using a known oscillatory input to the muscle in the form of electrical vestibular stimulation. Participants were exposed to sinusoidal vestibular stimuli while surface and intramuscular EMG were recorded from the left medial gastrocnemius. We compared the unrectified and rectified surface EMG to single motor units to determine which method best identified stimulus-EMG coherence and phase at the single-motor unit level. Surface EMG modulation at the stimulus frequency was obvious in the unrectified surface EMG. However, this modulation was not identified by the fast Fourier transform, and therefore stimulus coherence with the unrectified EMG signal failed to capture this covariance. Both the rectified surface EMG and single motor units displayed significant coherence over the entire stimulus bandwidth (1–20 Hz). Furthermore, the stimulus-phase relationship for the rectified EMG and motor units shared a moderate correlation ( r = 0.56). These data indicate that rectification of surface EMG is a necessary step to extract EMG envelope modulation due to motor unit entrainment to a known stimulus.

scholarly journals Preferential distribution of nociceptive input to motoneurons with muscle units in the cranial portion of the upper trapezius muscle

2016 ◽  
Vol 116 (2) ◽  
pp. 611-618 ◽  
Author(s):  
Jakob L. Dideriksen ◽  
Ales Holobar ◽  
Deborah Falla
Keyword(s):  
Motor Unit ◽  
Synaptic Input ◽  
Isotonic Saline ◽  
Trapezius Muscle ◽  
Motor Units ◽  
Noxious Stimulation ◽  
Caudal Region ◽  
Upper Trapezius ◽  
Upper Trapezius Muscle ◽  
Nociceptive Input

Pain is associated with changes in the neural drive to muscles. For the upper trapezius muscle, surface electromyography (EMG) recordings have indicated that acute noxious stimulation in either the cranial or the caudal region of the muscle leads to a relative decrease in muscle activity in the cranial region. It is, however, not known if this adaption reflects different recruitment thresholds of the upper trapezius motor units in the cranial and caudal region or a nonuniform nociceptive input to the motor units of both regions. This study investigated these potential mechanisms by direct motor unit identification. Motor unit activity was investigated with high-density surface EMG signals recorded from the upper trapezius muscle of 12 healthy volunteers during baseline, control (intramuscular injection of isotonic saline), and painful (hypertonic saline) conditions. The EMG was decomposed into individual motor unit spike trains. Motor unit discharge rates decreased significantly from control to pain conditions by 4.0 ± 3.6 pulses/s (pps) in the cranial region but not in the caudal region (1.4 ± 2.8 pps; not significant). These changes were compatible with variations in the synaptic input to the motoneurons of the two regions. These adjustments were observed, irrespective of the location of noxious stimulation. These results strongly indicate that the nociceptive synaptic input is distributed in a nonuniform way across regions of the upper trapezius muscle.

scholarly journals Assessment of force and fatigue in isometric contractions of the upper trapezius muscle by surface EMG signal and perceived exertion scale

2008 ◽  
Vol 28 (2) ◽  
pp. 179-186 ◽  
Author(s):  
Amedeo Troiano ◽  
Francesco Naddeo ◽  
Erik Sosso ◽  
Gianfranco Camarota ◽  
Roberto Merletti ◽  
...  
Keyword(s):  
Perceived Exertion ◽  
Trapezius Muscle ◽  
Surface Emg ◽  
Isometric Contractions ◽  
Upper Trapezius ◽  
Emg Signal ◽  
Upper Trapezius Muscle ◽  
Surface Emg Signal

Reliability of surface EMG matrix in locating the innervation zone of upper trapezius muscle

2011 ◽  
Vol 21 (5) ◽  
pp. 827-833 ◽  
Author(s):  
Marco Barbero ◽  
Roberto Gatti ◽  
Loredana Lo Conte ◽  
Fiona Macmillan ◽  
Fiona Coutts ◽  
...  
Keyword(s):  
Trapezius Muscle ◽  
Surface Emg ◽  
Innervation Zone ◽  
Upper Trapezius ◽  
Upper Trapezius Muscle

Conduction velocity of low-threshold motor units during ischemic contractions performed with surface EMG feedback

2005 ◽  
Vol 98 (4) ◽  
pp. 1487-1494 ◽  
Author(s):  
Dario Farina ◽  
Marco Gazzoni ◽  
Federico Camelia
Keyword(s):  
Motor Unit ◽  
Conduction Velocity ◽  
Action Potential Duration ◽  
Surface Emg ◽  
Mean Power ◽  
Single Motor Unit ◽  
Single Motor ◽  
Power Spectral ◽  
Low Threshold ◽  
Spectral Frequency

The aim of this study was to analyze the effect of ischemia on low-threshold motor unit conduction velocity. Nine subjects were trained to isolate the activity of a single motor unit (target motor unit) in the abductor pollicis brevis muscle with feedback on surface EMG signals recorded with a 16-electrode linear array. After training, the subjects activated the target motor unit at ∼8 pulses per second (pps) for five 3-min-long contractions. During the third and fourth contractions, a cuff inflated at 180 mmHg around the forearm induced ischemia of the hand. The exerted force (mean ± SE, 4.6 ± 2.1% of the maximal voluntary contraction force), discharge rate (8.6 ± 0.4 pps), interpulse interval variability (34.8 ± 2.5%), and peak-to-peak amplitude of the target motor unit action potentials (176.6 ± 18.2 μV) were not different among the five contractions. Conduction velocity, mean power spectral frequency, and action potential duration were the same in the beginning of the five contractions (2.8 ± 0.2 m/s, 195.2 ± 10.5 Hz, and 5.4 ± 0.3 ms, respectively) and changed over the 3 min of sustained activation only during the fourth contraction. Conduction velocity and mean power spectral frequency decreased (10.05 ± 1.8% and 8.50 ± 2.18% during the 3 min, respectively) and action potential duration increased (8.2 ± 4.6% in the 3 min) during the fourth contraction. In conclusion, 1) subjects were able to isolate the activity of a single motor unit with surface EMG visual feedback in ischemic conditions maintained for 16 min, and 2) the activation-induced decrease in single motor unit conduction velocity was significantly larger with ischemia than with normal circulation, probably due to the alteration of mechanisms of ion exchange across the fiber membrane.

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