scholarly journals Sex-related differences in motor unit firing rates and action potential amplitudes of the first dorsal interosseous during high-, but not low-intensity contractions

2020 ◽  
Vol 238 (5) ◽  
pp. 1133-1144
Author(s):  
Mandy E. Parra ◽  
Adam J. Sterczala ◽  
Jonathan D. Miller ◽  
Michael A. Trevino ◽  
Hannah L. Dimmick ◽  
...  
Keyword(s):  
Action Potential ◽  
Motor Unit ◽  
First Dorsal Interosseous ◽  
Firing Rates ◽  
Low Intensity ◽  
Motor Unit Firing

An examination of a potential organized motor unit firing rate and recruitment scheme of an antagonist muscle during isometric contractions

2021 ◽  
Author(s):  
Tanner Micah Reece ◽  
Trent J Herda
Keyword(s):  
Action Potential ◽  
Firing Rate ◽  
Motor Unit ◽  
Motor Unit Action Potential ◽  
Triceps Brachii ◽  
Antagonist Muscle ◽  
Recruitment Threshold ◽  
Firing Rates ◽  
Antagonist Muscles ◽  
Motor Unit Firing

The primary purpose of the present study is to determine if an organized control scheme exists for the antagonist muscle during steady isometric torque. A secondary focus is to better understand how firing rates of the antagonist muscle changes from a moderate- to higher-contraction intensity. Fourteen subjects performed two submaximal isometric trapezoid muscle actions of the forearm flexors that included a linearly increasing, steady force at both 40% and 70% maximum voluntary contraction, and linearly decreasing segments. Surface electromyographic signals of the biceps and triceps brachii were collected and decomposed into constituent motor unit action potential trains. Motor unit firing rate vs. recruitment threshold, motor unit action potential amplitude vs. recruitment threshold, and motor unit firing rate vs. action potential amplitude relationships of the biceps brachii (agonist) and triceps brachii (antagonist) muscles were analyzed. Moderate- to-strong relationships (|r| ³ 0.69) were present for the agonist and antagonist muscles for each relationship with no differences between muscles (p = 0.716, 0.428, 0.182). The y-intercepts of the motor unit firing rate vs. recruitment threshold relationship of the antagonist did not increase from 40% to 70% maximal voluntary contractions (p = 0.96), unlike for the agonist (p = 0.009). The antagonist muscle exhibits a similar motor unit control scheme to the agonist. Unlike the agonist, however, the firing rates of the antagonist did not increase with increasing intensity. Future research should investigate how antagonist firing rates adapt to resistance training and changes in antagonist firing rates in the absence of peripheral feedback.

Motor unit action potential amplitudes and firing rates during repetitive muscle actions of the first dorsal interosseous in children and adults

2019 ◽  
Vol 119 (4) ◽  
pp. 1007-1018 ◽  
Author(s):  
Jonathan D. Miller ◽  
Adam J. Sterczala ◽  
Michael A. Trevino ◽  
Mandy E. Wray ◽  
Hannah L. Dimmick ◽  
...  
Keyword(s):  
Action Potential ◽  
Motor Unit ◽  
Motor Unit Action Potential ◽  
First Dorsal Interosseous ◽  
Firing Rates ◽  
Motor Unit Action ◽  
Muscle Actions ◽  
Unit Action

The effect of blood flow on tibialis anterior motor unit firing rates during sustained low-intensity isometric contractions

2021 ◽  
Vol 46 (1) ◽  
pp. 63-68
Author(s):  
David B. Copithorne ◽  
Kalter Hali ◽  
Charles L. Rice
Keyword(s):  
Blood Flow ◽  
Motor Unit ◽  
Tibialis Anterior ◽  
Free Flow ◽  
Neural Activation ◽  
Firing Rates ◽  
Low Intensity ◽  
Motor Unit Firing ◽  
Blood Flow Occlusion ◽  
Flow Occlusion

Low-intensity contractions with blood flow occlusion (BFO) result in neuromuscular adaptations comparable with high-intensity (>70% maximal voluntary contraction, MVC) exercise. Because BFO exercise can only be applied to limb muscles, it is of interest to explore whether muscles proximal to the occlusion site are affected. Therefore, the purpose of this study was to assess neural activation of the tibialis anterior (TA) when flow is occluded proximal and distal to the active muscle. Five males completed three protocols to observe the effect of BFO on motor unit firing rates (MUFR) of the TA at a fatiguing contraction intensity of ∼15% MVC. Two occlusion protocols, one proximal (BFOprox) to and one distal (BFOdis) to the TA, were compared with a control (free-flow) protocol time-matched to BFOdis. MVC was significantly reduced following the BFOprox (∼41%; P < 0.001) and BFOdis (∼27%, P < 0.001), but not following the control protocol (∼15%; P = 0.13). Surface electromyography (EMG) during BFOdis and BFOprox increased ∼14% and ∼28%, respectively, but was not different among protocols. MUFRs for BFOdis and BFOprox were significantly reduced (by ∼33% and ∼23%, respectively; P < 0.01) at task failure. Results indicate that although BFOprox results in the largest reductions of MUFRs, BFOdis shows greater impairments compared with the free-flow control condition. Novelty Effects on motor unit firing rates of proximal versus distal blood flow occlusion were compared during low-intensity fatiguing task. Proximal occlusion results in greatest fatigue and reduction in motor unit rates, but distal occlusion elicits more fatigue and rate reduction than a control task.

Motor unit firing rates of the first dorsal interosseous differ between male and female children aged 8–10 years

2019 ◽  
Vol 66 ◽  
pp. 416-424 ◽  
Author(s):  
Trent J. Herda ◽  
Jonathan D. Miller ◽  
Mandy E. Wray ◽  
Adam J. Sterczala ◽  
Hannah L. Dimmick ◽  
...  
Keyword(s):  
Motor Unit ◽  
First Dorsal Interosseous ◽  
Male And Female ◽  
Firing Rates ◽  
Motor Unit Firing ◽  
Female Children

scholarly journals Sex-Related Differences in Muscle Composition and Motor Unit Firing Rates of the First Dorsal Interosseous

2018 ◽  
Vol 50 (5S) ◽  
pp. 8
Author(s):  
Mandy E. Wray ◽  
Adam J. Sterczala ◽  
Jonathan D. Miller ◽  
Hannah L. Dimmick ◽  
Trent J. Herda
Keyword(s):  
Motor Unit ◽  
First Dorsal Interosseous ◽  
Firing Rates ◽  
Muscle Composition ◽  
Motor Unit Firing

Differences in the motor unit firing rates and amplitudes in relation to recruitment thresholds during submaximal contractions of the first dorsal interosseous between chronically resistance-trained and physically active men

2018 ◽  
Vol 43 (8) ◽  
pp. 759-768 ◽  
Author(s):  
Adam J. Sterczala ◽  
Jonathan D. Miller ◽  
Michael A. Trevino ◽  
Hannah L. Dimmick ◽  
Trent J. Herda
Keyword(s):  
Motor Unit ◽  
Voluntary Contraction ◽  
Force Frequency ◽  
First Dorsal Interosseous ◽  
Physically Active ◽  
Firing Rates ◽  
Motor Unit Firing ◽  
Frequency Relationship ◽  
Muscle Actions ◽  
Active Controls

Previous investigations report no changes in motor unit (MU) firing rates during submaximal contractions following resistance training. These investigations did not account for MU recruitment or examine firing rates as a function of recruitment threshold (REC). Therefore, MU recruitment and firing rates in chronically resistance-trained (RT) and physically active controls (CON) were examined. Surface electromyography signals were collected from the first dorsal interosseous during isometric muscle actions at 40% and 70% maximal voluntary contraction (MVC). For each MU, force at REC, mean firing rate (MFR) during the steady force, and MU action potential amplitude (MUAPAMP) were analyzed. For each individual and contraction, the MFRs were linearly regressed against REC, whereas, exponential models were applied to the MFR versus MUAPAMP and MUAPAMP versus REC relationships with the y-intercepts and slopes (linear) and A and B terms (exponential) calculated. For the 40% MVC, the RT had less negative slopes (p = 0.001) and lower y-intercepts (p = 0.006) of the MFR versus REC relationships and lower B terms (p = 0.011) of the MUAPAMP versus REC relationships. There were no differences in either relationship between groups for the 70% MVC. During the 40% MVC, the RT had a smaller range of MFRs and MUAPAMPS in comparison with the CON, likely because of reduced MU recruitment. The RT had lower MFRs and recruitment during the 40% MVC, which may indicate a leftward shift in the force–frequency relationship, and thus require less excitation to the motoneuron pool to match the same relative force.

scholarly journals Effects Of Resistance Training On Maximal Motor Unit Firing Rates In Young And Older Males

2018 ◽  
Vol 50 (5S) ◽  
pp. 429-430
Author(s):  
Phuong L. Ha ◽  
Garrett M. Hester ◽  
Ryan J. Colquhoun ◽  
Mitchel A. Magrini ◽  
Zachary K. Pope ◽  
...  
Keyword(s):  
Resistance Training ◽  
Motor Unit ◽  
Firing Rates ◽  
Motor Unit Firing ◽  
Older Males

Neuromuscular drive and force production are not altered during bilateral contractions

1998 ◽  
Vol 84 (1) ◽  
pp. 200-206 ◽  
Author(s):  
J. M. Jakobi ◽  
E. Cafarelli
Keyword(s):  
Motor Unit ◽  
Force Production ◽  
Young Male ◽  
Neuromuscular Control ◽  
Force Generation ◽  
Isometric Contractions ◽  
Firing Rates ◽  
Significant Limitation ◽  
Motor Unit Firing ◽  
Male Subjects

Jakobi, J. M., and E. Cafarelli. Neuromuscular drive and force production are not altered during bilateral contractions. J. Appl. Physiol. 84(1): 200–206, 1998.—Several investigators have studied the deficit in maximal voluntary force that is said to occur when bilateral muscle groups contract simultaneously. A true bilateral deficit (BLD) would suggest a significant limitation of neuromuscular control; however, some of the data from studies in the literature are equivocal. Our purpose was to determine whether there is a BLD in the knee extensors of untrained young male subjects during isometric contractions and whether this deficit is associated with a decreased activation of the quadriceps, increased activation of the antagonist muscle, or an alteration in motor unit firing rates. Twenty subjects performed unilateral (UL) and bilateral (BL) isometric knee extensions at 25, 50, 75, and 100% maximal voluntary contraction. Total UL and BL force (Δ3%) and maximal rate of force generation (Δ2.5%) were not significantly different. Total UL and BL maximal vastus lateralis electromyographic activity (EMG; 2.7 ± 0.28 vs. 2.6 ± 0.24 mV) and coactivation (0.17 ± 0.02 vs. 0.20 ± 0.02 mV) were also not different. Similarly, the ratio of force to EMG during submaximal UL and BL contractions was not different. Analysis of force production by each leg in UL and BL conditions showed no differences in force, rate of force generation, EMG, motor unit firing rates, and coactivation. Finally, assessment of quadriceps activity with the twitch interpolation technique indicated no differences in the degree of voluntary muscle activation (UL: 93.6 ± 2.51 Hz, BL: 90.1 ± 2.43 Hz). These results provide no evidence of a significant limitation in neuromuscular control between BL and UL isometric contractions of the knee extensor muscles in young male subjects.

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