The Significance of Intramuscular Receptors in Load Compensation During Voluntary Contractions in Man

1973 ◽  
pp. 211-226 ◽  
Author(s):  
Å. B. Vallbo
Keyword(s):  
Load Compensation ◽  
Voluntary Contractions

scholarly journals Specific modulation of corticomuscular coherence during submaximal voluntary isometric, shortening and lengthening contractions

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Dorian Glories ◽  
Mathias Soulhol ◽  
David Amarantini ◽  
Julien Duclay
Keyword(s):  
H Reflex ◽  
Medial Gastrocnemius ◽  
Emg Activity ◽  
Beta Band ◽  
Lengthening Contractions ◽  
Time Frequency ◽  
Corticomuscular Coherence ◽  
Emg Signal ◽  
Voluntary Contractions ◽  
Spinal Excitability

AbstractDuring voluntary contractions, corticomuscular coherence (CMC) is thought to reflect a mutual interaction between cortical and muscle oscillatory activities, respectively measured by electroencephalography (EEG) and electromyography (EMG). However, it remains unclear whether CMC modulation would depend on the contribution of neural mechanisms acting at the spinal level. To this purpose, modulations of CMC were compared during submaximal isometric, shortening and lengthening contractions of the soleus (SOL) and the medial gastrocnemius (MG) with a concurrent analysis of changes in spinal excitability that may be reduced during lengthening contractions. Submaximal contractions intensity was set at 50% of the maximal SOL EMG activity. CMC was computed in the time–frequency domain between the Cz EEG electrode signal and the unrectified SOL or MG EMG signal. Spinal excitability was quantified through normalized Hoffmann (H) reflex amplitude. The results indicate that beta-band CMC and normalized H-reflex were significantly lower in SOL during lengthening compared with isometric contractions, but were similar in MG for all three muscle contraction types. Collectively, these results highlight an effect of contraction type on beta-band CMC, although it may differ between agonist synergist muscles. These novel findings also provide new evidence that beta-band CMC modulation may involve spinal regulatory mechanisms.

Comparison of single and multiple joint muscle functions and neural drive of trained athletes and untrained individuals

2021 ◽  
pp. 1-11
Author(s):  
Kale Mehmet
Keyword(s):  
Muscle Activation ◽  
Time Windows ◽  
Knee Extension ◽  
Electromechanical Delay ◽  
Neural Drive ◽  
Lower Limb Muscles ◽  
Explosive Force ◽  
Biarticular Muscle ◽  
Voluntary Contractions ◽  
Maximum Voluntary Force

BACKGROUND: There is insufficient knowledge about the rate of force development (RFD) characteristics over both single and multiple joint movements and the electromechanical delay (EMD) values obtained in athletes and untrained individuals. OBJECTIVE: To compare single and multiple joint functions and the neural drive of trained athletes and untrained individuals. METHODS: Eight trained athletes and 10 untrained individuals voluntarily participated to the study. The neuromuscular performance was assessed during explosive and maximum voluntary isometric contractions during leg press and knee extension related to single and multiple joint. Explosive force and surface electromyography of eight superficial lower limb muscles were measured in five 50-ms time windows from their onset, and normalized to peak force and electromyography activity at maximum voluntary force, respectively. The EMD was determined from explosive voluntary contractions (EVC’s). RESULTS: The results showed that there were significant differences in absolute forces during knee extension maximum voluntary force and EVC’s (p< 0.01) while trained athletes achieved greater relative forces than untrained individuals of EVC at all five time points (p< 0.05). CONCLUSIONS: The differences in explosive performance between trained athletes and untrained individuals in both movements may be explained by different levels of muscle activation within groups, attributed to variation in biarticular muscle function over both activities.

scholarly journals Test Re-test Reliability of Single and Multijoint Strength Properties in Female Australian Footballers

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Daniel Kadlec ◽  
Matthew J. Jordan ◽  
Leanne Snyder ◽  
Jacqueline Alderson ◽  
Sophia Nimphius
Keyword(s):  
Knee Flexion ◽  
Intraclass Correlation ◽  
Strength Properties ◽  
Peak Force ◽  
Test Reliability ◽  
Leg Extension ◽  
Hip Abduction ◽  
Hip Flexion ◽  
Voluntary Contractions ◽  
Trunk Position

Abstract Purpose To examine the test re-test reliability of isometric maximal voluntary contractions (MVC) of hip adduction (ADDISO), hip abduction (ABDISO), and multijoint leg extension (SQUATISO) in sub-elite female Australian footballers. Methods Data were collected from 24 sub-elite female Australian footballers (age 22.6 ± 4.5 years; height 169.4 ± 5.5 cm; body mass 66.6 ± 8.0 kg; 4.5 ± 4.4 years sport-specific training; 2.5 ± 2.0 years unstructured resistance training) from the same club on two non-consecutive days. Participants performed three isometric MVCs of ADDISO, ABDISO, and SQUATISO. The SQUATISO was performed at 140° knee flexion with a vertical trunk position and ADDISO and ABDISO measures were performed in a supine position at 60° of knee flexion and 60° hip flexion. Reliability was assessed using paired t tests and the intraclass correlation coefficient (ICC) with 95% confidence intervals (CI), typical error (TE), and coefficient of variation (CV%) with 95% CI. Results SQUATISO peak force (ICC .95; CV% 4.1), ABDISO for left, right, and sum (ICC .90–.92; CV% 5.0–5.7), and ADDISO for left, right, and sum (ICC .86–.91; CV% 6.2–6.9) were deemed acceptably reliable based on predetermined criteria (ICC ≥ .8 and CV% ≤ 10). Conclusion SQUATISO, ABDISO, and ADDISO tests demonstrated acceptable reliability for the assessment of peak force in sub-elite female Australian footballers, suggesting these assessments are suitable for muscle strength testing and monitoring adaptations to training.

scholarly journals Quadriceps activation during maximal isometric and isokinetic contractions: The minimal real difference and its implications

2020 ◽  
pp. 1-13
Author(s):  
Luigi Catino ◽  
Chiara Malloggi ◽  
Stefano Scarano ◽  
Valeria Cerina ◽  
Viviana Rota ◽  
...  
Keyword(s):  
Intraclass Correlation ◽  
Correlation Coefficients ◽  
Voluntary Activation ◽  
Real Difference ◽  
Concentric Contractions ◽  
Rehabilitation Programs ◽  
Logit Transformation ◽  
Isokinetic Contractions ◽  
Electrical Stimuli ◽  
Voluntary Contractions

BACKGROUND: A method of measurement of voluntary activation (VA, percent of full muscle recruitment) during isometric and isokinetic concentric contractions of the quadriceps femoris (QF) at 60∘/s and 120∘/s was previously validated. OBJECTIVE: This study aimed to quantify the test-retest minimal real difference (MRD) of VA during isometric (ISOM) and isokinetic concentric contractions of QF (100∘/s, ISOK) in a sample of healthy individuals. METHODS: VA was measured through the interpolated twitch technique. Pairs of electrical stimuli were delivered to the QF at 40∘ of knee flexion during maximal voluntary contractions. Twenty-five healthy participants (20–38 years, 12 women, 13 men) completed two testing sessions with a 14-day interval. VA values were linearized through logit transformation (VAl). The MRD was estimated from intraclass correlation coefficients (model 2.1). RESULTS: The VA (median, range) was 84.20% (38.2–99.9%) in ISOM and 94.22% (33.8-100%) in ISOK. MRD was 0.78 and 1.12 logit for ISOM and ISOK, respectively. As an example, in terms of percent VA these values correspond to a change from 76% to 95% and from 79% to 98% in ISOM and in ISOK, respectively. CONCLUSIONS: The provided MRD values allow to detect significant individual changes in VA, as expected after training and rehabilitation programs.

Respiratory load compensation in chronic airway obstruction

1985 ◽  
Vol 59 (6) ◽  
pp. 1947-1954 ◽  
Author(s):  
M. Lopata ◽  
E. Onal ◽  
G. Cromydas
Keyword(s):  
Airway Obstruction ◽  
Lung Volume ◽  
Average Rate ◽  
Minute Ventilation ◽  
Force Output ◽  
Transdiaphragmatic Pressure ◽  
Load Compensation ◽  
Group A ◽  
Group B ◽  
Chronic Airway

To assess respiratory neuromuscular function and load compensating ability in patients with chronic airway obstruction (CAO), we studied eight stable patients with irreversible airway obstruction during hyperoxic CO2 rebreathing with and without a 17 cmH2O X l-1 X s flow-resistive inspiratory load (IRL). Minute ventilation (VE), transdiaphragmatic pressure (Pdi), and diaphragmatic electromyogram (EMGdi) were monitored. Pdi and EMGdi were obtained via a single gastroesophageal catheter with EMGdi being quantitated as the average rate of rise of inspiratory (moving average) activity. Based on the effects of IRL on the Pdi response to CO2 [delta Pdi/delta arterial CO2 tension (PaCO2)] and the change in Pdi for a given change in EMGdi (delta Pdi/delta EMGdi) during rebreathing, two groups could be clearly identified. Four patients (group A) were able to increase delta Pdi/delta PaCO2 and delta Pdi/delta EMGdi, whereas in the other four (group B) the IRL responses decreased. All group B patients were hyperinflated having significantly greater functional residual capacity (FRC) and residual volume than group A. In addition the IRL induced percent change in delta Pdi/delta PaCO2, and delta VE/delta PaCO2 was negatively correlated with lung volume so that in the hyperinflated group B the higher the FRC the greater was the decrease in Pdi response due to IRL. In both groups the greater the FRC the greater was the decrease in the ventilatory response to loading. Patients with CAO, even with severe airways obstruction, can effect load compensation by increasing diaphragmatic force output, but the presence of increased lung volume with the associated shortened diaphragm prevents such load compensation.

scholarly journals Optimal Static Load Compensation With Fault Tolerance in Nonlinear Adaptive Structures Under Input and State Constraints

2020 ◽  
Vol 6 ◽  
Author(s):  
Julia L. Wagner ◽  
Andreas Gienger ◽  
Charlotte Stein ◽  
Philipp Arnold ◽  
Cristina Tarín ◽  
...  
Keyword(s):  
Fault Tolerance ◽  
State Constraints ◽  
Static Load ◽  
Adaptive Structures ◽  
Load Compensation ◽  
Input And State Constraints

Unilateral isometric muscle fatigue decreases force production and activation of contralateral knee extensors but not elbow flexors

2014 ◽  
Vol 39 (12) ◽  
pp. 1338-1344 ◽  
Author(s):  
Israel Halperin ◽  
David Copithorne ◽  
David G. Behm
Keyword(s):  
Muscle Fatigue ◽  
Force Production ◽  
Voluntary Activation ◽  
Knee Extensors ◽  
Elbow Flexors ◽  
Post Intervention ◽  
Nonlocal Effects ◽  
And Performance ◽  
Voluntary Contractions ◽  
Isometric Muscle

Nonlocal muscle fatigue occurs when fatiguing 1 muscle alters performance of another rested muscle. The purpose of the study was to investigate if fatiguing 2 separate muscles would affect the same rested muscle, and if fatiguing the same muscle would affect 2 separate muscles. Twenty-one trained males participated in 2 studies (n = 11; n = 10). Subjects performed 2 pre-test maximum voluntary contractions (MVCs) with the nondominant knee extensors. Thereafter they performed two 100-s MVCs with their dominant knee extensors, elbow flexors, or rested. Between and after the sets, a single MVC with the nondominant rested knee extensors was performed. Subsequently, 12 nondominant knee extensors repeated MVCs were completed. Force, quadriceps voluntary activation (VA), and electromyography (EMG) were measured. The same protocol was employed in study 2 except the nondominant elbow-flexors were tested. Study 1: Compared with control conditions, a significant decrease in nondominant knee extensors force, EMG, and VA was found under both fatiguing conditions (P ≤ 0.05; effect size (ES) = 0.91–1.15; 2%–8%). Additionally, decrements in all variables were found from the first post-intervention MVC to the last (P ≤ 0.05; ES = 0.82–2.40; 9%–20%). Study 2: No differences were found between conditions for all variables (P ≥ 0.33; ES ≤ 0.2; ≤3.0%). However, all variables decreased from the first post-intervention MVC to the last (P ≤ 0.05; ES = 0.4–3.0; 7.2%–19.7%). Whereas the rested knee extensors demonstrated nonlocal effects regardless of the muscle being fatigued, the elbow-flexors remained unaffected. This suggests that nonlocal effects are muscle specific, which may hold functional implications for training and performance.

scholarly journals Tracheal occlusion-evoked respiratory load compensation and inhibitory neurotransmitter expression in rats

2014 ◽  
Vol 116 (8) ◽  
pp. 1006-1016 ◽  
Author(s):  
Hsiu-Wen Tsai ◽  
Paul W. Davenport
Keyword(s):  
Neural Network ◽  
Brain Stem ◽  
Breathing Pattern ◽  
Respiratory Rhythm ◽  
Inhibitory Neurotransmitter ◽  
Load Compensation ◽  
Efferent Projections ◽  
Motor Reflex ◽  
Sensory Pathway ◽  
The Brain

Respiratory load compensation is a sensory-motor reflex generated in the brain stem respiratory neural network. The nucleus of the solitary tract (NTS) is thought to be the primary structure to process the respiratory load-related afferent activity and contribute to the modification of the breathing pattern by sending efferent projections to other structures in the brain stem respiratory neural network. The sensory pathway and motor responses of respiratory load compensation have been studied extensively; however, the mechanism of neurogenesis of load compensation is still unknown. A variety of studies has shown that inhibitory interconnections among the brain stem respiratory groups play critical roles for the genesis of respiratory rhythm and pattern. The purpose of this study was to examine whether inhibitory glycinergic neurons in the NTS were activated by external and transient tracheal occlusions (ETTO) in anesthetized animals. The results showed that ETTO produced load compensation responses with increased inspiratory, expiratory, and total breath time, as well as elevated activation of inhibitory glycinergic neurons in the caudal NTS (cNTS) and intermediate NTS (iNTS). Vagotomized animals receiving transient respiratory loads did not exhibit these load compensation responses. In addition, vagotomy significantly reduced the activation of inhibitory glycinergic neurons in the cNTS and iNTS. The results suggest that these activated inhibitory glycinergic neurons in the NTS might be essential for the neurogenesis of load compensation responses in anesthetized animals.

Reliability of the mechanomyogram detected with an accelerometer during voluntary contractions

2003 ◽  
Vol 41 (2) ◽  
pp. 198-202 ◽  
Author(s):  
M. Watakabe ◽  
K. Mita ◽  
K. Akataki ◽  
K. Ito
Keyword(s):  
Voluntary Contractions
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