Inter-individual variability among the mechanomyographic and electromyographic amplitude and mean power frequency responses during isometric ramp muscle actions
The purpose of this study was to examine the inter-individual variability in the patterns of responses for mechanomyographic (MMG) and electromyographic (EMG) amplitude and mean power frequency (MPF) of the vastus lateralis (VL) and rectusfemoris (RF) muscles during isometric ramp muscle actions of the leg extensors. Fifteen participants (mean +/- SD age = 24 +/- 4 years) performed two or three 6-s isometric ramp muscle actions with linear increases in torque from 15% to 90% of the highest maximal voluntary contraction (MVC) torque. Surface MMG and EMG signals were simultaneously recorded from the VL and RF muscles. The composite (averaged across subjects) and individual patterns of responses for the normalized MMG and EMG amplitude and MPF vs. isometric torque relationships were analyzed. The composite patterns for MMG amplitude for the VL and RF muscles were fit with cubic models, although, only 87% of the individual patterns (13 of 15 subjects) exhibited the same cubic pattern as the composite. For MMG MPF, the composite relationships were also cubic, but only 27% (4 subjects) and 40% (6 subjects) of the individuals exhibited the same patterns for the VL and RF respectively. 60% (8 subjects) of the individual EMG amplitude patterns of responses matched the same curvilinear composite patterns for the VL and RE, while only 7% (1 subject) and 27% (4 subjects) of the EMG MPF responses were similar to the composite models for the VL and RF muscles, respectively. Therefore, since the individual patterns did not always match the composite relationships (i.e., inter-individual variability), these findings suggested that the MMG and EMG amplitude and MPF vs. isometric torque relationships should be examined on a subject-by-subject and muscle-by-muscle basis during isometric ramp muscle actions.
Available from: Trent Herda
- "Barry and Cole (1990) and Orizio (1993) have suggested that these oscillations are manifested through (a) the gross lateral movement (GLM) of the muscle at the initiation of the contraction, (b) smaller subsequent lateral oscillations occurring at the resonant frequency of the muscle , and (c) dimensional changes in the active fibers. Numerous studies have utilized EMG and MMG simultaneously to examine motor unit control strategies during voluntary isometric ramp muscle actions (Akataki et al., 2004; Bilodeau et al., 1997; Cramer et al., 2004; Evetovich et al., 2003; Guo et al., 2010; Madeleine et al., 2001; Ryan et al., 2007). De Luca (de Luca et al., 1996) has suggested that the EMG amplitude-force relationship reflects the concurrent increases in motor unit recruitment and firing rates that regulate muscle force output, whereas, the MMG amplitude-force relationships have been able to distinguish between motor unit recruitment or rate coding as the primary mechanism to modulate force (Cooper, 2013). "
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ABSTRACT: The purpose of this study was to examine possible correlations between skinfold thicknesses and the a terms from the log-transformed electromyographic (EMGRMS) and mechanomyographic amplitude (MMGRMS)-force relationships, EMG M-Waves, and MMG gross lateral movements (GLM).
Forty healthy subjects performed a 6-s isometric ramp contraction from 5% to 85% of their maximal voluntary contraction with EMG and MMG sensors placed on the vastus lateralis (VL) and rectus femoris (RF). A single electrical stimulus was applied to the femoral nerve to record the EMG M-waves and MMG GLMs. Skinfold thickness was assessed at the site of each electrode. Pearson's product correlation coefficients were calculated comparing skinfold thicknesses with the a terms from the log-transformed EMGRMS-and MMGRMS-force relationships, EMG M-waves, and MMG GLMs.
There were no significant cor1relations (p>0.05) between the a terms and skinfold thicknesses for the RF and VL from the EMGRMS and MMGRMS-force relationships. However, there were significant correlations (p<0.05) between skinfold thicknesses and the EMG M-waves and MMG GLMs for the RF (r=-0.521, -0.376) and VL (r=-0.479, -0.484).
Relationships were only present between skinfold thickness and the amplitudes of the EMG and MMG signals during the non-voluntary muscle actions.
Journal of electromyography and kinesiology: official journal of the International Society of Electrophysiological Kinesiology 01/2014; 24(2). DOI:10.1016/j.jelekin.2013.12.005 · 1.65 Impact Factor
Available from: Clayton L Camic
- "Despite its broad applications, surface EMG is commonly used to examine motor control strategies, monitor muscle fatigue, assess neuromuscular alterations with aging, and track neurological diseases (De Luca 1984, Merletti et al 1990, Merletti et al 2002, Farina et al 2003). The surface EMG–force relationships are usually characterized as linear or quadratic increases in EMG amplitude across the force (or torque) spectrum (Beck et al 2007a, Ryan et al 2007). De Luca (1997) has suggested that the surface EMG–force relationships reflects the concurrent increases in motor unit recruitment and motor unit firing rates that regulate muscle force output. "
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ABSTRACT: The present study applied a log-transformation model to compare the electromyographic (EMG) amplitude versus torque relationships from monopolar EMG signals up to 35 mm proximal and distal from the innervation zone (IZ). Seven men (age = 23 ± 2 year; mass = 82 ± 10 kg) and two women (age = 21 ± 1 year; mass = 62 ± 8 kg) performed isometric ramp contractions of the right leg extensors with an eight-channel linear electrode array positioned over the vastus lateralis with the IZ located between channels 4 and 5. Linear regression models were fit to the log-transformed monopolar EMG(RMS)-torque relationships with the b terms (slope) and the a terms (Y-intercept) calculated for each channel and subject. The b terms for channels 4, 5, and 6 were higher (P ≤ 0.05) than the more distal channels 7 and 8 (P < 0.05). In contrast, there were no differences (P > 0.05) among the a terms of the eight channels. Thus, the shapes of the monopolar EMG(RMS)-torque relationships were altered as a function of distance between the IZ and recording area, which may be helpful for clinicians and researchers who infer changes in motor control strategies based on the shapes of the EMG(RMS)-torque relationships.
Physiological Measurement 03/2013; 34(3):315-24. DOI:10.1088/0967-3334/34/3/315 · 1.81 Impact Factor
Available from: Erdal Binboğa
- "medialis , and soleus mus - cles ) , which is primarily responsible for plantar flexion , but we did not measure the force generated by the same muscle group during plantar flexion . Despite the fact that EMG is highly correlated to the muscle force and the relationship is usually char - acterised as linear ( Beck et al . , 2007 ; De Luca , 1997 ; Ryan et al . , 2007"
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ABSTRACT: Abstract We investigated the effect of verbal encouragement on maximal voluntary contraction (MVC) level of the triceps surae muscle group. Our secondary focus was to examine whether the effect of verbal encouragement on MVC level varies as a result of conscientiousness. While the participants performed plantar flexion, MVCs of the triceps surae muscle group were measured using rectified and smoothed surface electromyography (rsEMG) during the absence and presence of verbal encouragement. Participants completed questions from the Five Factor Personality Inventory concerning conscientiousness and were divided into high- and low-conscientiousness groups according to a median split. The sample included 30 female and 53 male elite athletes. In the entire cohort, there was no significant difference in MVCs with and without verbal encouragement. When the sample was partitioned by conscientiousness scores, verbal encouragement led to a significant increase in MVC in the low-conscientiousness group, whereas verbal encouragement led to a non-significant decrease in MVC in the high-conscientiousness group. Percentage change in MVC across experimental conditions was significantly different between the groups, with a 9.72% increase during verbal encouragement of the low-conscientiousness group, and a 2.47% decrease during verbal encouragement of the high-conscientiousness group.
Journal of Sports Sciences 01/2013; 31(9). DOI:10.1080/02640414.2012.758869 · 2.25 Impact Factor
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