Motor unit spike counts before and after maximal voluntary contraction

1990 ◽  
Vol 13 (12) ◽  
pp. 1146-1151 ◽  
Author(s):  
Judith L. Gooch ◽  
Bruce Y. Newton ◽  
Jack H. Petajan
Keyword(s):  
Motor Unit ◽  
Maximal Voluntary Contraction ◽  
Voluntary Contraction ◽  
Before And After ◽  
Unit Spike

The Influence of Intermittent Fatigue Exercise on Early and Late Phases of Relaxation From Maximal Voluntary Contraction

1997 ◽  
Vol 22 (6) ◽  
pp. 573-584 ◽  
Author(s):  
Anna Jaskólska ◽  
Artur Jaskólski
Keyword(s):  
Relaxation Time ◽  
Relaxation Rate ◽  
Maximal Voluntary Contraction ◽  
Early Phase ◽  
Intermittent Exercise ◽  
Young Male ◽  
Voluntary Contraction ◽  
Hand Grip ◽  
Before And After ◽  
Late Relaxation Time

Twenty-two young male subjects were tested to estimate the behavior of the early and late phases of relaxation from a 3-s maximal voluntary contraction (MVC) under the influence of fatigue. Less demanding and more demanding protocols of intermittent hand grip exercise were used to fatigue muscle. Before and after fatigue, the early and late relaxation time, maximal relaxation rate, and half-relaxation time were measured. The results showed that during voluntary movement (a) the early phase of relaxation was independent of the mode of intermittent exercise and did not change significantly after fatigue; (b) the late relaxation time and absolute maximal relaxation rate were slower after both protocols, with the changes more pronounced following the more demanding protocol; and (c) the half-relaxation time and relative maximal relaxation rate were changed only in the more demanding protocol. It is concluded that unlike the relaxation following electrical stimulation of isolated muscle, the early phase of relaxation from voluntary contraction appears to be the most resistant to the type of intermittent fatiguing exercise used in the present study, whereas the late relaxation time was the most sensitive to this type of fatigue. Key words: hand grip exercise, late relaxation time, early relaxation time, half-relaxation time

Decrease in maximal voluntary contraction by tonic vibration applied to a single synergist muscle in humans

2000 ◽  
Vol 89 (4) ◽  
pp. 1420-1424 ◽  
Author(s):  
Motoki Kouzaki ◽  
Minoru Shinohara ◽  
Tetsuo Fukunaga
Keyword(s):  
Maximal Voluntary Contraction ◽  
Vastus Lateralis ◽  
Rectus Femoris ◽  
Knee Extension ◽  
Voluntary Contraction ◽  
Vastus Medialis ◽  
Force Development ◽  
Ia Afferent ◽  
Before And After ◽  
Integrated Emg

The purpose of the study was to examine the effect of prolonged tonic vibration applied to a single synergist muscle on maximal voluntary contraction (MVC) and maximal rate of force development (dF/d t max). The knee extension MVC force and surface electromyogram (EMG) from the rectus femoris (RF), vastus lateralis (VL), and vastus medialis (VM) during MVC were recorded before and after vibration of RF muscle at 30 Hz for 30 min. MVC, dF/d t max, and the integrated EMG (iEMG) of RF decreased significantly after prolonged tonic vibration in spite of no changes in iEMG of VL and VM. The present results indicate that MVC and dF/d t max may be influenced by the attenuated Ia afferent functions of a single synergist muscle.

scholarly journals Fatigue-induced adjustment in antagonist coactivation by old adults during a steadiness task

2016 ◽  
Vol 120 (9) ◽  
pp. 1039-1046 ◽  
Author(s):  
Christopher J. Arellano ◽  
David Caha ◽  
Joseph E. Hennessey ◽  
Ioannis G. Amiridis ◽  
Stéphane Baudry ◽  
...  
Keyword(s):  
Maximal Voluntary Contraction ◽  
Failure Time ◽  
Voluntary Contraction ◽  
Matching Task ◽  
Electromyographic Activity ◽  
Time To Failure ◽  
Old Adults ◽  
Before And After ◽  
Wrist Flexors ◽  
Maximal Voluntary Contraction Torque

The purpose of this study was to determine the adjustments in the level of coactivation during a steadiness task performed by young and old adults after the torque-generating capacity of the antagonist muscles was reduced by a fatiguing contraction. Torque steadiness (coefficient of variation) and electromyographic activity of the extensor and flexor carpi radialis muscles were measured as participants matched a wrist extensor target torque (10% maximum) before and after sustaining an isometric contraction (30% maximum) with wrist flexors to task failure. Time to failure was similar ( P = 0.631) for young (417 ± 121 s) and old (452 ± 174 s) adults. The reduction in maximal voluntary contraction torque (%initial) for the wrist flexors after the fatiguing contraction was greater ( P = 0.006) for young (32.5 ± 13.7%) than old (21.8 ± 6.6%) adults. Moreover, maximal voluntary contraction torque for the wrist extensors declined for old (−13.7 ± 12.7%; P = 0.030), but not young (−5.4 ± 13.8%; P = 0.167), adults. Torque steadiness during the matching task with the wrist extensors was similar before and after the fatiguing contraction for both groups, but the level of coactivation increased after the fatiguing contraction for old ( P = 0.049) but not young ( P = 0.137) adults and was twice the amplitude for old adults ( P = 0.002). These data reveal that old adults are able to adjust the amount of antagonist muscle activity independent of the agonist muscle during steady submaximal contractions.

scholarly journals Motor unit firing patterns on increasing force during force and position tasks

2021 ◽  
Author(s):  
Shun Kunugi ◽  
Ales Holobar ◽  
Tsutomu Kodera ◽  
Heishiro Toyoda ◽  
Kohei Watanabe
Keyword(s):  
Firing Rate ◽  
Motor Unit ◽  
Maximal Voluntary Contraction ◽  
Gastrocnemius Muscle ◽  
Voluntary Contraction ◽  
Medial Gastrocnemius ◽  
Firing Patterns ◽  
Motor Unit Firing ◽  
The Difference ◽  
Medial Gastrocnemius Muscle

Different neurophysiological strategies are used to perform angle adjustments during motor tasks such as car driving and force-control tasks using a fixed-rigid pedal. However, the difference in motor unit behavior in response to an increasing exerted force between tasks is unknown. This study aimed to investigate the difference in motor unit responsiveness on increasing force between force and position tasks. Twelve healthy participants performed ramp and hold contractions during ankle plantarflexion at 20 and 30% of the maximal voluntary contraction using a rigid pedal (force task) and a free pedal with an inertial load (position task). High-density surface electromyograms were recorded of the medial gastrocnemius muscle and decomposed into individual motor unit firing patterns. Ninety and 109 motor units could be tracked between different target torques in each task. The mean firing rate increased and firing rate variability decreased on 10% maximal voluntary contraction force gain during both force and position tasks. There were no significant differences in these responses between the two tasks. Our results suggest that the motor unit firing rate is similarly regulated between force and position tasks in the medial gastrocnemius muscle with an increase in the exerted force.

Force Perception before and after Maximal Voluntary Contraction

1993 ◽  
Vol 76 (2) ◽  
pp. 399-402 ◽  
Author(s):  
Judith L. Gooch ◽  
Jeffrey Randle
Keyword(s):  
Maximal Voluntary Contraction ◽  
Elbow Flexion ◽  
Voluntary Contraction ◽  
Low Level ◽  
Force Perception ◽  
Before And After ◽  
The Mean ◽  
Flexion Force

Capacity to match a low level of elbow flexion force maintained in the control arm was measured in the experimental arm in 16 subjects before and after maximal voluntary contraction (MVC). Prior to a 1-min. MVC, the mean force exerted by the experimental arm was 3.4 ± 1.0 kg when attempting to match the tension of a 2.3-kg weight in the control arm. After the MVC, the mean force exerted in the experimental arm was 4.4 ± 2.6 kg. The change in perception of force after a prolonged MVC as demonstrated in this study may be due to postcontraction potentiation of contraction, which has been demonstrated by others after a brief MVC.

scholarly journals Effect of Acute Static Stretching on the Activation Patterns Using High-Density Surface Electromyography of the Gastrocnemius Muscle during Ramp-Up Task

Sensors ◽  
2021 ◽  
Vol 21 (14) ◽  
pp. 4841
Author(s):  
Noriaki Maeda ◽  
Makoto Komiya ◽  
Yuichi Nishikawa ◽  
Masanori Morikawa ◽  
Shogo Tsutsumi ◽  
...  
Keyword(s):  
Motor Unit ◽  
Muscle Activation ◽  
Gastrocnemius Muscle ◽  
Peak Torque ◽  
Voluntary Contraction ◽  
Motor Unit Recruitment ◽  
Static Stretching ◽  
Activation Patterns ◽  
Muscle Activation Patterns ◽  
Before And After

This study aimed to evaluate motor unit recruitment during submaximal voluntary ramp contraction in the medial head of the gastrocnemius muscle (MG) by high-density spatial electromyography (SEMG) before and after static stretching (SS) in healthy young adults. SS for gastrocnemius was performed in 15 healthy participants for 2 min. Normalized peak torque by bodyweight of the plantar flexor, muscle activity at peak torque, and muscle activation patterns during ramp-up task were evaluated before and after SS. Motor unit recruitment during the submaximal voluntary contraction of the MG was measured using SEMG when performing submaximal ramp contractions during isometric ankle plantar flexion from 30 to 80% of the maximum voluntary contraction (MVC). To evaluate the changes in the potential distribution of SEMG, the root mean square (RMS), modified entropy, and coefficient of variation (CV) were calculated from the dense surface EMG data when 10% of the MVC force was applied. Muscle activation patterns during the 30 to 80% of MVC submaximal voluntary contraction tasks were significantly changed from 50 to 70% of MVC after SS when compared to before. The variations in motor unit recruitment after SS indicate diverse motor unit recruitments and inhomogeneous muscle activities, which may adversely affect the performance of sports activities.

Effects of Concentric and Eccentric Strength Training on Fatigue Induced by Concentric and Eccentric Exercises

2019 ◽  
Vol 14 (1) ◽  
pp. 91-98 ◽  
Author(s):  
Eduardo Lusa Cadore ◽  
Miriam González-Izal ◽  
Rafael Grazioli ◽  
Igor Setuain ◽  
Ronei Silveira Pinto ◽  
...  
Keyword(s):  
Maximal Voluntary Contraction ◽  
Isometric Force ◽  
Vastus Lateralis ◽  
Voluntary Contraction ◽  
Eccentric Training ◽  
Echo Intensity ◽  
Rate Of Torque Development ◽  
Before And After ◽  
Torque Development ◽  
Similar Force

Purpose: To compare the concentric and eccentric training effects on fatigue induced by eccentric and concentric protocols. Methods: A total of 22 men and women (22 [3.6] y) were assigned to concentric (GCON, n = 11) or eccentric training (GECC, n = 11). The concentric (CON) and eccentric (ECC) protocols were composed of 4 sets of 20 knee-extension/flexion repetitions. Force losses were analyzed by comparing 10 repetitions’ mean torques during the protocols and by verifying the maximal voluntary contraction and rate of torque development before and after the protocols. Muscle damage was assessed using echo intensity of the vastus lateralis 48 h after the protocols. Training consisted of 6 wk of isokinetic exercise at 60°/s (concentric or eccentric) twice weekly. Results: Before training, both protocols resulted in dynamic and isometric force losses in GCON and GECC (P < .01), but the magnitude was greater after the CON protocol than after the ECC protocol (P < .001). After training, both GCON and GECC showed similar force decreases during the CON and ECC protocols (P < .01), and these changes were not different from the pretraining decreases. Regarding maximal voluntary contraction after training, GECC showed lower force decreases than GCON after ECC exercise (−13.7% vs −22.3%, respectively, P < .05), whereas GCON showed lower maximal voluntary contraction decreases after CON exercise compared with pretraining (−29.2%, P < .05). Losses in rate of torque development were similar after the protocols before and after the training regimens. No changes in echo intensity were observed after the protocols before and after training. Conclusion: Both interventions resulted in similar force decreases during fatigue protocols compared with those associated with pretraining.

Changes in motor unit discharge rate are not associated with the amount of twitch potentiation in old men

2002 ◽  
Vol 93 (5) ◽  
pp. 1616-1621 ◽  
Author(s):  
C. S. Klein ◽  
C. L. Rice ◽  
T. D. Ivanova ◽  
S. J. Garland
Keyword(s):  
Motor Unit ◽  
Maximal Voluntary Contraction ◽  
Discharge Rate ◽  
Voluntary Contraction ◽  
Triceps Brachii ◽  
Unit Discharge ◽  
Twitch Force ◽  
Twitch Potentiation ◽  
Motor Unit Discharge ◽  
Old Men

This study examined, in nine old men (82 ± 4 yr), whether there is an association between the magnitude of change in motor unit discharge rate and the amount of twitch potentiation after a conditioning contraction (CC). The evoked twitch force and motor unit discharge rate during isometric ramp-and-hold contractions (10–18 s) of the triceps brachii muscle at 10, 20, and 30% of the maximal voluntary contraction were determined before and 10 s, 2 min, 6 min, and 11 min after a 5-s CC at 75% maximal voluntary contraction. After the CC, there was a potentiation of twitch force (approximately twofold), and the discharge rate of the 47 sampled motor units declined ( P < 0.05) an average of 1 Hz 10 s after the CC, compared with the control condition. The CC had no effect on the variability (coefficient of variation) of both force and discharge rate, as well as the electromyographic activity recorded over the triceps brachii and biceps brachii muscles. In contrast to our earlier study of young men (Klein CS, Ivanova TD, Rice CL, and Garland SJ, Neurosci Lett 316: 153–156, 2001), the magnitude of the reduction in discharge rate after the CC was not associated ( r = 0.06) with the amount of twitch potentiation. These findings suggest an age-related alteration in the neural strategy for adjusting motor output to a muscle after a CC.

Difference in aftereffects following prolonged Achilles tendon vibration on muscle activity during maximal voluntary contraction among plantar flexor synergists

2005 ◽  
Vol 98 (4) ◽  
pp. 1427-1433 ◽  
Author(s):  
Junichi Ushiyama ◽  
Kei Masani ◽  
Motoki Kouzaki ◽  
Hiroaki Kanehisa ◽  
Tetsuo Fukunaga
Keyword(s):  
Achilles Tendon ◽  
Muscle Activity ◽  
Maximal Voluntary Contraction ◽  
Plantar Flexion ◽  
Voluntary Contraction ◽  
High Threshold ◽  
Plantar Flexor ◽  
Afferent Activity ◽  
Ia Afferent ◽  
Before And After

It has been suggested that a suppression of maximal voluntary contraction (MVC) induced by prolonged vibration is due to an attenuation of Ia afferent activity. The purpose of the present study was to test the hypothesis that aftereffects following prolonged vibration on muscle activity during MVC differ among plantar flexor synergists owing to a supposed difference in muscle fiber composition. The plantar flexion MVC torque and surface electromyogram (EMG) of the medial head of gastrocnemius (MG), the lateral head of gastrocnemius (LG), and the soleus (Sol) were recorded in 13 subjects before and after prolonged vibration applied to the Achilles tendon at 100 Hz for 30 min. The maximal H reflexes and M waves were also determined from the three muscles, and the ratio between H reflexes and M waves (H/Mmax) was calculated before and after the vibration. The MVC torque was decreased by 16.6 ± 3.7% after the vibration ( P < 0.05; ANOVA). The H/Mmax also decreased for all three muscles, indicating that Ia afferent activity was successfully attenuated by the vibration in all plantar flexors. However, a reduction of EMG during MVC was observed only in MG (12.7 ± 4.0%) and LG (11.4 ± 3.9%) ( P < 0.05; ANOVA), not in Sol (3.4 ± 3.0%). These results demonstrated that prolonged vibration-induced MVC suppression was attributable mainly to the reduction of muscle activity in MG and LG, both of which have a larger proportion of fast-twitch muscle fibers than Sol. This finding suggests that Ia-afferent activity that reinforces the recruitment of high-threshold motor units is necessary to enhance force exertion during MVC.

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