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.

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

scholarly journals Effect of blood flow occlusion on corticospinal excitability during sustained low-intensity isometric elbow flexion

2020 ◽  
Vol 123 (3) ◽  
pp. 1113-1119 ◽  
Author(s):  
D. B. Copithorne ◽  
C. L. Rice ◽  
C. J. McNeil
Keyword(s):  
Blood Flow ◽  
Evoked Potential ◽  
Motor Evoked Potential ◽  
Elbow Flexion ◽  
Group Iii ◽  
Low Intensity ◽  
Blood Flow Occlusion ◽  
Motor Cortical ◽  
Flow Occlusion ◽  
Contractile Failure

Blood flow occlusion (BFO) has been used to study the influence of group III/IV muscle afferents after fatiguing exercise, but it is unknown how BFO-induced activity of these afferents affects motor cortical and motoneuronal excitability during low-intensity exercise. Therefore, the purpose of this study was to assess the acute effect of BFO on peripheral [maximal M wave (Mmax)], spinal [cervicomedullary motor evoked potential (CMEP) normalized to Mmax], and motor cortical [motor evoked potential (MEP) normalized to CMEP] excitability. Nine healthy men completed a sustained isometric contraction of the elbow flexors at 20% of maximal force under three conditions: 1) contractile failure with BFO, 2) a time-matched trial without restriction [free flow (FFiso)], and 3) contractile failure with free flow (FFfail). Time to failure for BFO (and FFiso) were ~80% shorter than that for FFfail ( P < 0.05). For FFfail and FFiso, Mmax area decreased ~17% and ~7%, respectively ( P < 0.05), with no change during BFO. CMEP/Mmax area increased ~226% and ~80% during BFO and FFfail, respectively ( P < 0.05), with no change during FFiso ( P > 0.05). The increase in normalized CMEP area was greater for BFO and FFfail compared with FFiso and for BFO compared with FFfail. MEP/CMEP area was not different among the protocols ( P > 0.05) and increased ~64% with time ( P < 0.05). It is likely that group III/IV muscle afferent feedback to the spinal cord modulates the large increase in motoneuronal excitability for the BFO compared with FFfail and FFiso protocols. NEW & NOTEWORTHY We have observed how blood flow occlusion modulates motor cortical, spinal, and peripheral excitability during and immediately after a sustained low-intensity isometric elbow flexion contraction to failure. We conclude that blood flow occlusion causes a greater and more rapid increase in motoneuronal excitability.

Motor unit firing rates and contractile properties in tibialis anterior of young and old men

1999 ◽  
Vol 87 (2) ◽  
pp. 843-852 ◽  
Author(s):  
Denise M. Connelly ◽  
Charles L. Rice ◽  
Martin R. Roos ◽  
Anthony A. Vandervoort
Keyword(s):  
Motor Unit ◽  
Tibialis Anterior ◽  
Tibialis Anterior Muscle ◽  
Young Men ◽  
Contractile Properties ◽  
Firing Rates ◽  
Twitch Contraction ◽  
Age Related ◽  
Motor Unit Firing ◽  
Old Men

The effects of aging on motoneuron firing rates and muscle contractile properties were studied in tibialis anterior muscle by comparing results from six young (20.8 ± 0.8 yr) and six old men (82.0 ± 1.7 yr). For each subject, data were collected from repeated tests over a 2-wk period. Contractile tests included maximal voluntary contraction (MVC) with twitch interpolation and stimulated twitch contractions. The old men had 26% lower MVC torque ( P < 0.01) than did the young men, but percent activation was not different (99.1 and 99.3%, respectively). Twitch contraction durations were 23% longer ( P < 0.01) in the old compared with the young men. During a series of repeated brief steady-state contractions at 10, 25, 50, 75, and 100% MVC, motor unit firing rates were recorded. Results from ∼950 motor unit trains in each subject group indicated that at all relative torque levels mean firing rates were 30–35% lower ( P < 0.01) in the old subjects. Comparisons between young and old subjects’ mean firing rates at each of 10%, 50%, and MVC torques and their corresponding mean twitch contraction duration yielded a range of moderate-to-high correlations ( r = −0.67 to −0.84). That lower firing rates were matched to longer twitch contraction durations in the muscle of old men, and relatively higher firing rates were matched with shorter contraction times from the young men, indirectly supports the neuromuscular age-related remodeling principle.

scholarly journals The Relationship Between Blood Flow and Motor Unit Firing Rates in Response to Fatiguing Exercise Post-stroke

2019 ◽  
Vol 10 ◽  
Author(s):  
Spencer Murphy ◽  
Matthew Durand ◽  
Francesco Negro ◽  
Dario Farina ◽  
Sandra Hunter ◽  
...  
Keyword(s):  
Blood Flow ◽  
Motor Unit ◽  
Firing Rates ◽  
Post Stroke ◽  
Motor Unit Firing ◽  
Fatiguing Exercise ◽  
The Relationship

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

scholarly journals Exercise and Repeated Testing Improves Accuracy of Laser Doppler Assessment of Microvascular Function Following Shortened (1-minute) Blood Flow Occlusion

2016 ◽  
Vol 23 (4) ◽  
pp. 293-300 ◽  
Author(s):  
Brian D. Tran ◽  
Abraham Chiu ◽  
Charlene Tran ◽  
Danica Rose Rogacion ◽  
Nicole Tfaye ◽  
...  
Keyword(s):  
Blood Flow ◽  
Microvascular Function ◽  
Laser Doppler ◽  
Repeated Testing ◽  
Blood Flow Occlusion ◽  
Flow Occlusion

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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