Theoretical analysis of surface EMG in voluntary isometric contraction

1979 ◽  
Vol 40 (3) ◽  
pp. 155-164 ◽  
Author(s):  
H. Miyano ◽  
T. Sadoyama
Keyword(s):  
Theoretical Analysis ◽  
Isometric Contraction ◽  
Surface Emg

Changes of muscular sound during sustained isometric contraction up to exhaustion

1989 ◽  
Vol 66 (4) ◽  
pp. 1593-1598 ◽  
Author(s):  
C. Orizio ◽  
R. Perini ◽  
A. Veicsteinas
Keyword(s):  
Isometric Contraction ◽  
Exercise Intensity ◽  
Maximum Voluntary Contraction ◽  
Isometric Exercise ◽  
Surface Emg ◽  
Voluntary Contraction ◽  
Biceps Muscle ◽  
Output Force ◽  
Contact Transducer ◽  
Four Levels

The sound (SMG) generated by the biceps muscle during isometric exercise at 20, 40, 60, and 80% of maximum voluntary contraction (MVC) up to exhaustion has been recorded by a contact transducer and integrated (iSMG), together with the surface electromyogram (EMG) in eight young untrained men. At the onset of exercise, iSMG and integrated surface EMG (iEMG) amplitude increased linearly with exercise. iSMG remained constant for 253 +/- 73 (SD), 45 +/- 16, 21 +/- 5, and 0 s at the four levels of contraction. Then iSMG increased linearly at 20% MVC, fluctuated at 40% MVC, and decreased exponentially at 60 and 80% MVC. iSMG exhaustion-to-onset ratio was 5.0 at 20%, 1.0 at 40%, and 0.2 at 60 and 80% MVC. On the contrary, independently of exercise intensity, iEMG increased with time, being 1.4 higher at exhaustion than at the onset. The nonunivocal iSMG changes with time and effort of exercise suggest that the sound may be a useful tool to acquire different information to EMG and output force during muscle contraction up to fatigue.

scholarly journals A comparison of two gluteus maximus EMG maximum voluntary isometric contraction positions

PeerJ ◽  
2015 ◽  
Vol 3 ◽  
pp. e1261 ◽  
Author(s):  
Bret Contreras ◽  
Andrew D. Vigotsky ◽  
Brad J. Schoenfeld ◽  
Chris Beardsley ◽  
John Cronin
Keyword(s):  
Body Mass ◽  
Isometric Contraction ◽  
Gluteus Maximus ◽  
Surface Emg ◽  
Future Research ◽  
Maximum Voluntary Isometric Contraction ◽  
Heterogeneous Samples ◽  
Hip Extension ◽  
Emg Electrodes

Background.The purpose of this study was to compare the peak electromyography (EMG) of the most commonly-used position in the literature, the prone bent-leg (90°) hip extension against manual resistance applied to the distal thigh (PRONE), to a novel position, the standing glute squeeze (SQUEEZE).Methods.Surface EMG electrodes were placed on the upper and lower gluteus maximus of thirteen recreationally active females (age = 28.9 years; height = 164 cm; body mass = 58.2 kg), before three maximum voluntary isometric contraction (MVIC) trials for each position were obtained in a randomized, counterbalanced fashion.Results.No statistically significant (p< 0.05) differences were observed between PRONE (upper: 91.94%; lower: 94.52%) and SQUEEZE (upper: 92.04%; lower: 85.12%) for both the upper and lower gluteus maximus. Neither the PRONE nor SQUEEZE was more effective between all subjects.Conclusions.In agreement with other studies, no single testing position is ideal for every participant. Therefore, it is recommended that investigators employ multiple MVIC positions, when possible, to ensure accuracy. Future research should investigate a variety of gluteus maximus MVIC positions in heterogeneous samples.

scholarly journals Rotation of Motoneurons During Prolonged Isometric Contractions in Humans

2006 ◽  
Vol 96 (3) ◽  
pp. 1135-1140 ◽  
Author(s):  
Parveen Bawa ◽  
Marco Y. Pang ◽  
Kari A. Olesen ◽  
Blair Calancie
Keyword(s):  
Motor Unit ◽  
Isometric Contraction ◽  
Motor Units ◽  
Surface Emg ◽  
Neuromuscular Fatigue ◽  
Isometric Contractions ◽  
Muscle Type ◽  
Rotation Surface ◽  
Metabolic Recovery ◽  
The Subject

Prolonged and weak isometric contractions can result in neuromuscular fatigue. Alternation of discharge of motor units with similar thresholds (termed rotation) could be useful to minimize neuromuscular fatigue by providing periods for metabolic recovery of the contractile elements. In the present study, we investigated the prevalence of motoneuron rotation during prolonged contractions of distal limb muscles. Electromyographic (EMG; needle and surface) was recorded from muscles of the forearm and distal leg. The subject made a slowly increasing isometric contraction to recruit and discharge a motor unit ( 1) for a prolonged period of time (>30 min). Sometimes an additional motor unit ( 2) was recruited in which case the subject relaxed the contraction slightly so that only one motor unit remained tonic. Often it was this newly recruited motor unit (i.e., unit 2) that continued discharging, while motor unit 1 fell silent. Continued contraction would then lead to the resumption of tonic discharge of unit 1 and silence of unit 2. This would complete a rotation between motor units 1 and 2. During prolonged contractions, rotation was observed in ∼80% of the motor-unit pairs examined. There was no difference in rotation incidence by muscle type. For the unit pairs showing rotation, surface EMG values were significantly higher immediately prior to rotation than after rotation had occurred. Our findings show that rotation of motor units with similar recruitment thresholds during such contractions is common in distal muscles of the arm and leg and may help offset neuromuscular fatigue.

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