Neuromuscular fatigue development during maximal concentric and isometric knee extensions

2006 ◽  
Vol 100 (3) ◽  
pp. 780-785 ◽  
Author(s):  
Nicolas Babault ◽  
Kevin Desbrosses ◽  
Marie-Sophie Fabre ◽  
Anne Michaut ◽  
Michel Pousson
Keyword(s):  
Root Mean Square ◽  
Vastus Lateralis ◽  
Neuromuscular Fatigue ◽  
Peripheral Fatigue ◽  
Vastus Lateralis Muscle ◽  
Electromyographic Activity ◽  
Median Frequency ◽  
Mean Square ◽  
Fatigue Development ◽  
Frequency Changes

This study aimed to investigate mechanisms of neuromuscular fatigue during maximal concentric and isometric leg extensions inducing similar torque decrements. Nine physically active men performed two separate fatiguing sessions maintained until similar torque decreases were obtained. The first session, only conducted under isokinetic concentric conditions (CON), consisted of three series of 30 maximal voluntary concentric knee extensions (60°/s). The second session, exclusively isometric (ISO), mimicked the torque decreases registered during the CON session while performing three long-lasting ISO contractions. Maximal voluntary torque, activation level (twitch interpolation technique), electromyographic activity (root mean square and median frequency) of the vastus lateralis muscle, and electrically evoked doublet-twitch mechanical properties were measured before and at the end of each of the three series. After the three series, similar torque decrements were obtained for both fatiguing procedures. The total fatiguing contraction durations were not different among procedures. With equivalent voluntary torque decrements, the doublet-twitch amplitude reduction was significantly greater ( P < 0.01) during the two first series of the CON procedure compared with ISO. No difference was observed for the third series. Although no difference was recorded with fatigue for median frequency changes between CON and ISO, activation levels and root mean square values demonstrated greater reductions ( P < 0.05) for all three series during the ISO procedure compared with CON. Performing CON or ISO fatiguing exercises demonstrated different fatigue origins. With CON exercises, peripheral fatigue developed first, followed by central fatigue, whereas with ISO exercises the fatigue pattern was inverted.

scholarly journals Exploratory study of electromyographic behavior of the vastus medialis and vastus lateralis at neuromuscular fatigue onset

2014 ◽  
Vol 20 (2) ◽  
pp. 213-220 ◽  
Author(s):  
Cristiano Rocha da Silva ◽  
Danilo de Oliveira Silva ◽  
Deisi Ferrari ◽  
Rúben de Faria Negrão Filho ◽  
Neri Alves ◽  
...  
Keyword(s):  
Exploratory Study ◽  
Vastus Lateralis ◽  
Knee Extension ◽  
Neuromuscular Fatigue ◽  
Isometric Contractions ◽  
Median Frequency ◽  
Vastus Medialis ◽  
Mean Square ◽  
Electromyographic Signal ◽  
The Moment

This study aimed to determine and analyze the neuromuscular fatigue onset by median frequency (MDF) and the root mean square (RMS) behavior of an electromyographic signal (EMG). Eighteen healthy men with no prior knee problems initially performed three maximum voluntary isometric contractions (MVIC). After two days of MVIC test, participants performed a fatiguing protocol in which they performed submaximal knee-extension contractions at 20% and 70% MVIC held to exhaustion. The MDF and RMS values from the EMG signals were recorded from the vastus medialis (VM) and the vastus lateralis (VL). Analysis of the MDF and RMS behavior enabled identification of neuromuscular fatigue onset for VM and VL muscles in 20% and 70% loads. Alterations between the VM and VL in the neuromuscular fatigue onset, at 20% and 70% MVIC, were not significant. These findings suggest that the methodology proposal was capable of indicating minute differences sensible to alterations in the EMG signals, allowing identification of the moment when the MDF and the RMS showed significant changes in behavior. The methodology used was also a viable one for describing and identifying the neuromuscular fatigue onset by means of the analysis of EMG signals.

Distinct profiles of neuromuscular fatigue during muscle contractions below and above the critical torque in humans

2012 ◽  
Vol 113 (2) ◽  
pp. 215-223 ◽  
Author(s):  
Mark Burnley ◽  
Anni Vanhatalo ◽  
Andrew M. Jones
Keyword(s):  
Vastus Lateralis ◽  
Central Fatigue ◽  
Neuromuscular Fatigue ◽  
Voluntary Activation ◽  
Peripheral Fatigue ◽  
Critical Threshold ◽  
Task Failure ◽  
Fatigue Development ◽  
The Right ◽  
Experimental Trials

Whether the transition in fatigue processes between “low-intensity” and “high-intensity” contractions occurs gradually, as the torque requirements are increased, or whether this transition occurs more suddenly at some identifiable “threshold”, is not known. We hypothesized that the critical torque (CT; the asymptote of the torque-duration relationship) would demarcate distinct profiles of central and peripheral fatigue during intermittent isometric quadriceps contractions (3-s contraction, 2-s rest). Nine healthy men performed seven experimental trials to task failure or for up to 60 min, with maximal voluntary contractions (MVCs) performed at the end of each minute. The first five trials were performed to determine CT [∼35–55% MVC, denoted severe 1 (S1) to severe 5 (S5) in ascending order], while the remaining two trials were performed 10 and 20% below the CT (denoted CT-10% and CT-20%). Dynamometer torque and the electromyogram of the right vastus lateralis were sampled continuously. Peripheral and central fatigue was determined from the fall in potentiated doublet torque and voluntary activation, respectively. Above CT, contractions progressed to task failure in ∼3–18 min, at which point the MVC did not differ from the target torque (S1 target, 88.7 ± 4.3 N·m vs. MVC, 89.3 ± 8.8 N·m, P = 0.94). The potentiated doublet fell significantly in all trials, and voluntary activation was reduced in trials S1–S3, but not trials S4 and S5. Below CT, contractions could be sustained for 60 min on 17 of 18 occasions. Both central and peripheral fatigue developed, but there was a substantial reserve in MVC torque at the end of the task. The rate of global and peripheral fatigue development was four to five times greater during S1 than during CT-10% (change in MVC/change in time S1 vs. CT-10%: −7.2 ± 1.4 vs. −1.5 ± 0.4 N·m·min−1). These results demonstrate that CT represents a critical threshold for neuromuscular fatigue development.

Activation imbalances in lumbar spine muscles in the presence of chronic low back pain

2003 ◽  
Vol 94 (4) ◽  
pp. 1410-1420 ◽  
Author(s):  
Lars I. E. Oddsson ◽  
Carlo J. De Luca
Keyword(s):  
Low Back Pain ◽  
Back Pain ◽  
Root Mean Square ◽  
Chronic Low Back Pain ◽  
Neuromuscular Fatigue ◽  
Emg Activity ◽  
Median Frequency ◽  
Low Back ◽  
Mean Square ◽  
Root Mean Square Amplitude

Paraspinal electromyographic (EMG) activity was recorded bilaterally from three lumbar levels during 30-s isometric trunk extensions [40 and 80% of maximum voluntary contraction (MVC)] in 20 healthy men and 14 chronic low back pain patients in pain. EMG parameters indicating neuromuscular fatigue and contralateral imbalances in EMG root-mean-square amplitude and median frequency were analyzed. Patients in pain showed less fatigue than controls at both contraction levels and produced only 55% of their MVC. Patients in pain likely did not produce a “true” maximum effort. A low MVC estimate would mean lower absolute contraction levels and less neuromuscular fatigue, thus explaining lower scores in the patients. Contralateral root-mean-square amplitude imbalances were present in both categories of subjects although such imbalances, when averaged across lumbar levels, were significantly larger in patients. Median frequency imbalances were significantly larger in the patients, at segmental as well as across lumbar levels. These results suggest that the presence of pain in these patients caused a redistribution of the activation behavior between synergistic muscles of the lumbar back.

scholarly journals Quadriceps short-term resistance exercise in subjects with resistant hypertension

2011 ◽  
Vol 24 (4) ◽  
pp. 629-636 ◽  
Author(s):  
Arthur de Sá Ferreira ◽  
Juliana Flávia de Oliveira ◽  
Ivan Cordovil ◽  
José Barbosa Filho
Keyword(s):  
Resistance Exercise ◽  
Root Mean Square ◽  
Resistant Hypertension ◽  
Pharmacological Treatment ◽  
Vastus Lateralis ◽  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Median Frequency ◽  
Mean Square ◽  
Arterial Blood

INTRODUCTION: Resistant arterial hypertension may lead to muscle disuse and reduced functional capacity due to arterial and target-organs lesions. The main objective of this work is to evaluate the quadriceps strength and fatigue tolerance after a program of resistance exercise in subjects with resistant primary hypertension. METHODS: Six patients under pharmacological treatment were submitted to a four-week resistance exercise training program for the quadriceps (8-14 repetitions, 3 sets, 3 days per week). Strength was evaluated by isometric dynamometry, as the percentage change in maximum voluntary contraction over the four week program. Fatigue was analyzed by surface electromyography, as the change in both root mean square value and intercept of median frequency slope of vastus medialis and vastus lateralis. RESULTS: Significant increase in the maximum voluntary contraction was observed (p = 0.04). Fatigue tolerance was not improved as seen by root mean square as well as in the intercept of median frequency (p > 0.05). Additionally, no significant changes were observed in resting arterial blood pressure and heart rate throughout the training period. CONCLUSION: The prescribed protocol seemed to successfully increase localized muscle strength without negatively affecting the monitored cardiovascular variables in patients with resistant hypertension under pharmacological treatment.

scholarly journals ELECTROMYOGRAPIC ACTIVITY OF THE ABDOMINAL AND PARAVERTEBRAL MUSCLES DURING COFFEE HARVESTING

2020 ◽  
Vol 26 (3) ◽  
pp. 225-229
Author(s):  
Edmar de Lima ◽  
Thiago Oliveira Santos ◽  
Wonder Passoni Higino ◽  
Renato Aparecido de Souza ◽  
Fabiano Fernandes da Silva
Keyword(s):  
Root Mean Square ◽  
Abdominal Muscles ◽  
Electromyographic Activity ◽  
Median Frequency ◽  
Mean Square ◽  
Level Of Evidence ◽  
Rural Workers ◽  
Rural Worker ◽  
Paravertebral Muscles ◽  
The Many

ABSTRACT Introduction The rural worker involved in the coffee harvest is an important person for the economy of the many countries. However, scientific studies on the health of this worker are rare. Objective To analyze the lumbar paravertebral musculature and abdominal rectus of rural workers during coffee harvesting with the manual machines with different footrest bases (inclined, declined and horizontal), by means of electromyography. Methods Eight male rural workers from the region of Muzambinho participated in the study. All procedures and electromyographic routines were applied according to the SENIAN protocol. The workers made the usual coffee harvesting movements, using the manual machine for one minute. The data are expressed as means and standard deviations. The RMS (root mean square) signal and the median frequency (FM) were also analyzed. Results It was observed that the type of footrest base did not influence the electromyographic activity RMS or the FM, but we found that the paravertebral muscles have greater electromyographic activation when compared to the abdominal muscles, regardless of the type of footrest base. Conclusion For the task performed, the paravertebral muscles present greater electromyographic activation compared to the abdominal rectus. Level of Evidence III; Diagnostic studies - Investigating a diagnostic test.

Reciprocal Coactivation Patterns of the Lateral and Medial Quadriceps and Hamstrings during Low- and Moderate-Speed Isokinetic Movement

1998 ◽  
Vol 7 (3) ◽  
pp. 182-196 ◽  
Author(s):  
Ronald V. Croce ◽  
John P. Miller ◽  
Robert Confessore ◽  
James C. Vailas
Keyword(s):  
Knee Joint ◽  
Female Athletes ◽  
Vastus Lateralis ◽  
Biceps Femoris ◽  
Median Frequency ◽  
Vastus Medialis ◽  
Mean Square ◽  
Joint Movement ◽  
Surface Electrodes ◽  
Emg Patterns

The purpose of this study was to examine coactivation patterns of the lateral and medial quadriceps and the lateral and medial hamstrings during low- and moderate-speed isokinetic movements. Twelve female athletes performed isokinetic knee assessments at 60 and 180°/s. Root mean square electromyographic (rmsEMG) activity and the median frequency of the EMG (mfEMG) were determined by placing bipolar surface electrodes on the vastus lateralis (VL), vastus medialis (VM), biceps femoris (BF), and medial hamstrings (MH). Results of rmsEMG indicated that the VM showed almost twice the coactivation of the VL (p< .05), and that the BF showed almost four times the coactivation of the MH (p <.05). Finally, differences were noted in the mfEMG (p< .05), with the VM displaying different recruitment patterns at 180°/s as an agonist compared to that as an antagonist. Results indicated that when acting as antagonists, the VM and BE display the greatest EMG patterns during isokinetic knee joint movement.

scholarly journals Effects of different vibration frequencies, amplitudes and contraction levels on lower limb muscles during graded isometric contractions superimposed on whole body vibration stimulation

2019 ◽  
Vol 6 ◽  
pp. 205566831982746 ◽  
Author(s):  
Amit N Pujari ◽  
Richard D Neilson ◽  
Marco Cardinale
Keyword(s):  
Isometric Contraction ◽  
Vastus Lateralis ◽  
Whole Body Vibration ◽  
Biceps Femoris ◽  
Whole Body ◽  
Isometric Contractions ◽  
Electromyographic Activity ◽  
Mean Square ◽  
Body Vibration ◽  
Neuromuscular Activity

Background Indirect vibration stimulation, i.e., whole body vibration or upper limb vibration, has been investigated increasingly as an exercise intervention for rehabilitation applications. However, there is a lack of evidence regarding the effects of graded isometric contractions superimposed on whole body vibration stimulation. Hence, the objective of this study was to quantify and analyse the effects of variations in the vibration parameters and contraction levels on the neuromuscular responses to isometric exercise superimposed on whole body vibration stimulation. Methods In this study, we assessed the ‘neuromuscular effects’ of graded isometric contractions, of 20%, 40%, 60%, 80% and 100% of maximum voluntary contraction, superimposed on whole body vibration stimulation (V) and control (C), i.e., no-vibration in 12 healthy volunteers. Vibration stimuli tested were 30 Hz and 50 Hz frequencies and 0.5 mm and 1.5 mm amplitude. Surface electromyographic activity of the vastus lateralis, vastus medialis and biceps femoris were measured during V and C conditions with electromyographic root mean square and electromyographic mean frequency values used to quantify muscle activity and their fatigue levels, respectively. Results Both the prime mover (vastus lateralis) and the antagonist (biceps femoris) displayed significantly higher (P < 0.05) electromyographic activity with the V than the C condition with varying percentage increases in EMG root-mean-square (EMGrms) values ranging from 20% to 200%. For both the vastus lateralis and biceps femoris, the increase in mean EMGrms values depended on the frequency, amplitude and muscle contraction level with 50 Hz–0.5 mm stimulation inducing the largest neuromuscular activity. Conclusions These results show that the isometric contraction superimposed on vibration stimulation leads to higher neuromuscular activity compared to isometric contraction alone in the lower limbs. The combination of the vibration frequency with the amplitude and the muscle tension together grades the final neuromuscular output.

scholarly journals Test-retest reliability of electromyographic signal parameters used to evaluate neuromuscular fatigue in quadriceps femoris muscle

Kinesiology ◽  
2016 ◽  
Vol 48 (2) ◽  
pp. 174-181 ◽  
Author(s):  
Cristiano Rocha da Silva ◽  
Danilo de Oliveira Silva ◽  
Ronaldo Valdir Briani ◽  
Marcella Ferraz Pazzinatto ◽  
Deisi Ferrari ◽  
...  
Keyword(s):  
Vastus Lateralis ◽  
Rectus Femoris ◽  
Neuromuscular Fatigue ◽  
Median Frequency ◽  
Endurance Time ◽  
Retest Reliability ◽  
Emg Signal ◽  
Electromyographic Signal ◽  
Test Retest Reliability ◽  
Voluntary Contractions

The purpose of this study was to analyze the test-retest reliability of the median frequency (MDF) and root mean square (RMS) used to determine the onset of neuromuscular fatigue (NF) during sustained fatiguing contractions of the quadriceps. Eighteen healthy men were tested on two days, and electromyographic (EMG) signals were recorded from the vastus medialis (VM), rectus femoris (RF) and vastus lateralis (VL) during sustained isometric contractions at 20 and 70% of maximum voluntary contractions (MVC) held until exhaustion. The reliability of endurance time was excellent at 20% MVC and poor at 70% MVC. EMG variables were evaluated: (1) at the beginning of the test; (2) at NF; and (3) at the end of the test. The NF time values presented poor reliability. The MDF has shown, in general, poor reliability at 20 and 70% MVC, whereas the RMS reliability presented better results for both loads, especially for RF, followed by the VM and VL muscles. The MDF and RMS values extracted from NF showed poor reliability at 20 and 70% MVC, which suggests caution in using these variables extracted from the EMG signal to determine the onset of NF.

scholarly journals A Methodological Framework to Capture Neuromuscular Fatigue Mechanisms Under Stress

2021 ◽  
Vol 2 ◽  
Author(s):  
Oshin Tyagi ◽  
Ranjana K. Mehta
Keyword(s):  
Imaging Techniques ◽  
Motor Evoked Potential ◽  
Silent Period ◽  
Central Fatigue ◽  
Brain Regions ◽  
Functional Brain Imaging ◽  
Neuromuscular Fatigue ◽  
Voluntary Activation ◽  
Electromyographic Activity ◽  
Fatigue Development

Neuromuscular fatigue is exacerbated under stress and is characterized by shorter endurance time, greater perceived effort, lower force steadiness, and higher electromyographic activity. However, the underlying mechanisms of fatigue under stress are not well-understood. This review investigated existing methods of identifying central mechanisms of neuromuscular fatigue and the potential mechanisms of the influence of stress on neuromuscular fatigue. We found that the influence of stress on the activity of the prefrontal cortex, which are also involved in exercise regulation, may contribute to exacerbated fatigue under stress. We also found that the traditional methods involve the synchronized use of transcranial magnetic stimulation, peripheral nerve stimulation, and electromyography to identify the contribution of supraspinal fatigue, through measures such as voluntary activation, motor evoked potential, and silent period. However, these popular techniques are unable to provide information about neural alterations upstream of the descending drive that may contribute to supraspinal fatigue development. To address this gap, we propose that functional brain imaging techniques, which provide insights on activation and information flow between brain regions, need to be combined with the traditional measures of measuring central fatigue to fully understand the mechanisms behind the influence of stress on fatigue.

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