Training History-Dependent Functional Role of EMG Model-Predicted Antagonist Moments in Knee Extensor Moment Generation in Healthy Young Adults

Resistance training (RT) improves the skeletal muscle’s ability to generate maximal voluntary force and is accompanied by changes in the activation of the antagonist muscle which is not targeted primarily by RT. However, the nature and role of neural adaptation to RT in the antagonist muscle is paradoxical and not well understood. We compared moments, agonist muscle activation, antagonist activation, agonist-antagonist coactivation, and electromyographic (EMG) model-predicted moments generated by antagonist hamstring muscle coactivation during isokinetic knee extension in leg strength-trained (n = 10) and untrained (n = 11) healthy, younger adults. Trained vs. untrained adults were up to 58% stronger. During knee extension, hamstring activation was 1.6-fold greater in trained vs. untrained adults (p = 0.022). This hamstring activation produced 2.6-fold greater model-predicted antagonist moments during knee extension in the trained (42.7 ± 19.55 Nm) vs. untrained group (16.4 ± 12.18 Nm; p = 0.004), which counteracted (reduced) quadriceps knee extensor moments ~43 Nm (0.54 Nm·kg−1) and by ~16 Nm (0.25 Nm·kg−1) in trained vs. untrained. Antagonist hamstring coactivation correlated with decreases and increases, respectively, in quadriceps moments in trained and untrained. The EMG model-predicted antagonist moments revealed training history-dependent functional roles in knee extensor moment generation.

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Initial phase of maximal voluntary and electrically stimulated knee extension torque development at different knee angles

Journal of Applied Physiology ◽

10.1152/japplphysiol.00230.2004 ◽

2004 ◽

Vol 97 (5) ◽

pp. 1693-1701 ◽

Cited By ~ 118

Author(s):

C. J. de Ruiter ◽

R. D. Kooistra ◽

M. I. Paalman ◽

A. de Haan

Keyword(s):

Muscle Activation ◽

Knee Extensor ◽

Surface Emg ◽

Knee Extension ◽

Voluntary Contraction ◽

Voluntary Activation ◽

Knee Angle ◽

Time Integral ◽

Voluntary Contractions ◽

Torque Development

We investigated the capacity for torque development and muscle activation at the onset of fast voluntary isometric knee extensions at 30, 60, and 90° knee angle. Experiments were performed in subjects ( n = 7) who had high levels (>90%) of activation at the plateau of maximal voluntary contractions. During maximal electrical nerve stimulation (8 pulses at 300 Hz), the maximal rate of torque development (MRTD) and torque time integral over the first 40 ms (TTI40) changed in proportion with torque at the different knee angles (highest values at 60°). At each knee angle, voluntary MRTD and stimulated MRTD were similar ( P < 0.05), but time to voluntary MRTD was significantly longer. Voluntary TTI40 was independent ( P > 0.05) of knee angle and on average (all subjects and angles) only 40% of stimulated TTI40. However, among subjects, the averaged (across knee angles) values ranged from 10.3 ± 3.1 to 83.3 ± 3.2% and were positively related ( r2 = 0.75, P < 0.05) to the knee-extensor surface EMG at the start of torque development. It was concluded that, although all subjects had high levels of voluntary activation at the plateau of maximal voluntary contraction, among subjects and independent of knee angle, the capacity for fast muscle activation varied substantially. Moreover, in all subjects, torque developed considerably faster during maximal electrical stimulation than during maximal voluntary effort. At different knee angles, stimulated MRTD and TTI40 changed in proportion with stimulated torque, but voluntary MRTD and TTI40 changed less than maximal voluntary torque.

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Brain Activation During Maximum Concentric and Eccentric Knee Extension Muscle Contractions

10.31487/j.jbn.2020.01.05 ◽

2020 ◽

pp. 1-6

Author(s):

Ali Sharifnezhad ◽

Moein Koohestani ◽

Ali Sharifnezhad ◽

Ali Abbasi ◽

Amir-Homayoun Javadi ◽

...

Keyword(s):

Muscle Activation ◽

Task Complexity ◽

Control Strategies ◽

Knee Extensor ◽

Eccentric Contraction ◽

Cortical Activity ◽

Knee Extension ◽

Muscle Contractions ◽

System Control ◽

Alpha Power

Purpose: In spite of mounting evidence indicating that concentric and eccentric knee extensor muscle contractions might have special nervous system control strategies, the differentiation of brain frequencies between concentric and eccentric movements and how the motor cortex programs this contraction has been less studied. In this study, the brain and muscle activation differences during maximum concentric and eccentric contractions were compared. Methods: Nine healthy volunteers performed 20 maximum eccentric and 20 maximum concentric knee extensor contractions. Electroencephalography (EEG) signals from sensorimotor-related cortical areas were recorded simultaneous with the electromyography (EMG) of the knee extensor muscles. In the spectral analysis the performance related power values were calculated for Theta (4-7 Hz) and Alpha (7-12 Hz). Results: The time-domain results revealed, longer time and greater cortical activity is required for the preparation of an eccentric contraction. For the eccentric task, the cortical activity was greater, but the EMG was lower in comparison to the concentric task values. Statistical analysis showed significant higher and lower Theta and Alpha power in both types of contractions compared to the resting state, respectively. Conclusion: These findings suggest that increased Theta power is associated with task complexity and focused attention and decreased Alpha power values with increased information processing in the somatosensory cortex.

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Comparison of quadriceps muscle activation in exercises with different duration of concentric and eccentric contractions

Archivos de Medicina del Deporte ◽

10.18176/archmeddeporte.0002 ◽

2020 ◽

Vol 37 (5) ◽

pp. 291-297

Author(s):

G Freire da Silva ◽

F Douglas Tourino ◽

RC Ribeiro Diniz ◽

L Túlio de Lacerda ◽

HC Martins Costa ◽

...

Keyword(s):

Degrees Of Freedom ◽

Muscle Activation ◽

Vastus Lateralis ◽

Knee Extensor ◽

Rectus Femoris ◽

Quadriceps Muscle ◽

Knee Extension ◽

Muscle Action ◽

Emg Signal ◽

Knee Extension Exercise

Aim: The objective of the present study was to compare the amplitude of the electromyographic (EMG) signal of the quadriceps muscle portions vastus medialis (VM), vastus lateralis (VL) and rectus femoris (RF) and the activation ratio (VM/VL, VM/RF and VL/RF) in protocols with different durations of concentric and eccentric muscular actions. Material and method: Twelve female volunteers performed the knee extensor exercise with two different protocols [1s for concentric muscle action and 5s for eccentric muscle action (1:5); 5s of concentric muscle action and 1s of eccentric muscle action (5:1)] and 3 sets of 6 repetitions, 180s of pause between each sets and a intensity of 50% of 1RM. The root mean square of the amplitude of the normalized EMG signal was calculated for each repetition in each series. Results: it was observed an increase in the activation of the VM and VL portions in equivalent repetitions of each series and for the VL portion, the 1: 5 protocol provided greater activation compared to the other protocol. No differences were found for muscles activation ratios VM/RF and VL/RF, being that for the VM/VL ratio there was only change at one repetition. Conclusion: The results suggest that the portions of the quadriceps muscle may present different EMG responses in similar protocols, but this fact may not interfere in the synergism between them. The reduced degrees of freedom of the knee extension exercise and the characteristics of the protocols adopted may be the elements that contributed to the limited alterations that occurred in the present study.

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Agonist-Antagonist Coactivation Enhances Corticomotor Excitability of Ankle Muscles

Neural Plasticity ◽

10.1155/2019/5190671 ◽

2019 ◽

Vol 2019 ◽

pp. 1-12

Author(s):

Trisha M. Kesar ◽

Andrew Tan ◽

Steven Eicholtz ◽

Kayilan Baker ◽

Jiang Xu ◽

...

Keyword(s):

Neural Control ◽

Muscle Activation ◽

Motor Evoked Potentials ◽

Experimental Session ◽

Antagonist Muscle ◽

Corticomotor Excitability ◽

Flexion Extension ◽

Cord Injury ◽

Methodological Considerations ◽

Antagonist Coactivation

Spinal pathways underlying reciprocal flexion-extension contractions have been well characterized, but the extent to which cortically evoked motor-evoked potentials (MEPs) are influenced by antagonist muscle activation remains unclear. A majority of studies using transcranial magnetic stimulation- (TMS-) evoked MEPs to evaluate the excitability of the corticospinal pathway focus on upper extremity muscles. Due to functional and neural control differences between lower and upper limb muscles, there is a need to evaluate methodological factors influencing TMS-evoked MEPs specifically in lower limb musculature. If and to what extent the activation of the nontargeted muscles, such as antagonists, affects TMS-evoked MEPs is poorly understood, and such gaps in our knowledge may limit the rigor and reproducibility of TMS studies. Here, we evaluated the effect of the activation state of the antagonist muscle on TMS-evoked MEPs obtained from the target (agonist) ankle muscle for both tibialis anterior (TA) and soleus muscles. Fourteen able-bodied participants (11 females, age: 26.1±4.1 years) completed one experimental session; data from 12 individuals were included in the analysis. TMS was delivered during 4 conditions: rest, TA activated, soleus activated, and TA and soleus coactivation. Three pairwise comparisons were made for MEP amplitude and coefficient of variability (CV): rest versus coactivation, rest versus antagonist activation, and agonist activation versus coactivation. We demonstrated that agonist-antagonist coactivation enhanced MEP amplitude and reduced MEP CVs for both TA and soleus muscles. Our results provide methodological considerations for future TMS studies and pave the way for future exploration of coactivation-dependent modulation of corticomotor excitability in pathological cohorts such as stroke or spinal cord injury.

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The effects of agonist and antagonist muscle activation on the knee extension moment–angle relationship in adults and children

European Journal of Applied Physiology ◽

10.1007/s00421-009-1088-4 ◽

2009 ◽

Vol 106 (6) ◽

pp. 849-856 ◽

Cited By ~ 26

Author(s):

Thomas D. O’Brien ◽

Neil D. Reeves ◽

Vasilios Baltzopoulos ◽

David A. Jones ◽

Constantinos N. Maganaris

Keyword(s):

Muscle Activation ◽

Knee Extension ◽

Antagonist Muscle ◽

Agonist And Antagonist ◽

Adults And Children

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Ischemic conditioning increases strength and volitional activation of paretic muscle in chronic stroke: a pilot study

Journal of Applied Physiology ◽

10.1152/japplphysiol.01072.2017 ◽

2018 ◽

Vol 124 (5) ◽

pp. 1140-1147 ◽

Cited By ~ 15

Author(s):

Allison S. Hyngstrom ◽

Spencer A. Murphy ◽

Jennifer Nguyen ◽

Brian D. Schmit ◽

Francesco Negro ◽

...

Keyword(s):

Motor Unit ◽

Muscle Activation ◽

Knee Extensor ◽

Chronic Stroke ◽

Motor Unit Recruitment ◽

Stroke Survivors ◽

Single Session ◽

Ischemic Conditioning ◽

Leg Strength ◽

Knee Extensor Strength

Ischemic conditioning (IC) on the arm or leg has emerged as an intervention to improve strength and performance in healthy populations, but the effects on neurological populations are unknown. The purpose of this study was to quantify the effects of a single session of IC on knee extensor strength and muscle activation in chronic stroke survivors. Maximal knee extensor torque measurements and surface EMG were quantified in 10 chronic stroke survivors (>1 yr poststroke) with hemiparesis before and after a single session of IC or sham on the paretic leg. IC consisted of 5 min of compression with a proximal thigh cuff (inflation pressure = 225 mmHg for IC or 25 mmHg for sham) followed by 5 min of rest. This was repeated five times. Maximal knee extensor strength, EMG magnitude, and motor unit firing behavior were measured before and immediately after IC or sham. IC increased paretic leg strength by 10.6 ± 8.5 Nm, whereas no difference was observed in the sham group (change in sham = 1.3 ± 2.9 Nm, P = 0.001 IC vs. sham). IC-induced increases in strength were accompanied by a 31 ± 15% increase in the magnitude of muscle EMG during maximal contractions and a 5% decrease in motor unit recruitment thresholds during submaximal contractions. Individuals who had the most asymmetry in strength between their paretic and nonparetic legs had the largest increases in strength ( r2 = 0.54). This study provides evidence that a single session of IC can increase strength through improved muscle activation in chronic stroke survivors. NEW & NOTEWORTHY Present rehabilitation strategies for chronic stroke survivors do not optimally activate paretic muscle, and this limits potential strength gains. Ischemic conditioning of a limb has emerged as an effective strategy to improve muscle performance in healthy individuals but has never been tested in neurological populations. In this study, we show that ischemic conditioning on the paretic leg of chronic stroke survivors can increase leg strength and muscle activation while reducing motor unit recruitment thresholds.

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Older Compared With Younger Adults Performed 467 Fewer Sit-to-Stand Trials, Accompanied by Small Changes in Muscle Activation and Voluntary Force

Frontiers in Aging Neuroscience ◽

10.3389/fnagi.2021.679282 ◽

2021 ◽

Vol 13 ◽

Author(s):

Paulo Cezar Rocha dos Santos ◽

Claudine J. C. Lamoth ◽

Lilian Teresa Bucken Gobbi ◽

Inge Zijdewind ◽

Fabio Augusto Barbieri ◽

...

Keyword(s):

Muscle Activation ◽

Perceived Exertion ◽

Knee Extension ◽

Age Effects ◽

Younger Adults ◽

Perturbation Model ◽

Sit To Stand ◽

Rate Of Perceived Exertion ◽

Isometric Knee Extension ◽

Extension Force

Background: Repetitive sit-to-stand (rSTS) is a fatigue perturbation model to examine the age-effects on adaptability in posture and gait, yet the age-effects on muscle activation during rSTS per se are unclear. We examined the effects of age and exhaustive rSTS on muscle activation magnitude, onset, and duration during ascent and descent phases of the STS task.Methods: Healthy older (n = 12) and younger (n = 11) adults performed rSTS, at a controlled frequency dictated by a metronome (2 s for cycle), to failure or for 30 min. We assessed muscle activation magnitude, onset, and duration of plantar flexors, dorsiflexors, knee flexors, knee extensors, and hip stabilizers during the initial and late stages of rSTS. Before and after rSTS, we measured maximal voluntary isometric knee extension force, and rate of perceived exertion, which was also recorded during rSTS task.Results: Older vs. younger adults generated 35% lower maximum voluntary isometric knee extension force. During the initial stage of rSTS, older vs. younger adults activated the dorsiflexor 60% higher, all 5 muscle groups 37% longer, and the hip stabilizers 80% earlier. Older vs. younger adults completed 467 fewer STS trials and, at failure, their rate of perceived exertion was ~17 of 20 on the Borg scale. At the end of the rSTS, maximum voluntary isometric knee extension force decreased 16% similarly in older and younger, as well as the similar age groups decline in activation of the dorsiflexor and knee extensor muscles (all p < 0.05).Conclusion: By performing 467 fewer STS trials, older adults minimized the potential effects of fatigability on muscle activation, voluntary force, and motor function. Such a sparing effect may explain the minimal changes in gait after rSTS reported in previous studies, suggesting a limited scope of this perturbation model to probe age-effects on muscle adaptation in functional tasks.

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The role of reminding in retroactive effects of memory for older and younger adults.

Psychology and Aging ◽

10.1037/pag0000427 ◽

2020 ◽

Vol 35 (5) ◽

pp. 697-709

Author(s):

Sydney M. Garlitch ◽

Christopher N. Wahlheim

Keyword(s):

Younger Adults

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

Isokinetics and Exercise Science ◽

10.3233/ies-203225 ◽

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.

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The Pleiotropic Function of Human Sirtuins as Modulators of Metabolic Pathways and Viral Infections

Cells ◽

10.3390/cells10020460 ◽

2021 ◽

Vol 10 (2) ◽

pp. 460

Author(s):

Mohammed Hamed Alqarni ◽

Ahmed Ibrahim Foudah ◽

Magdy Mohamed Muharram ◽

Nikolaos E. Labrou

Keyword(s):

Metabolic Pathways ◽

Histone Deacetylases ◽

Viral Infections ◽

Cell Physiology ◽

Functional Roles ◽

Regulatory Processes ◽

Complex Functions ◽

Natural Polyphenol ◽

Antiviral Targets

Sirtuins (SIRTs) are nicotinamide adenine dinucleotide-dependent histone deacetylases that incorporate complex functions in the mechanisms of cell physiology. Mammals have seven distinct members of the SIRT family (SIRT1-7), which play an important role in a well-maintained network of metabolic pathways that control and adapt the cell to the environment, energy availability and cellular stress. Until recently, very few studies investigated the role of SIRTs in modulating viral infection and progeny. Recent studies have demonstrated that SIRT1 and SIRT2 are promising antiviral targets because of their specific connection to numerous metabolic and regulatory processes affected during infection. In the present review, we summarize some of the recent progress in SIRTs biochemistry and their emerging function as antiviral targets. We also discuss the potential of natural polyphenol-based SIRT modulators to control their functional roles in several diseases including viral infections.

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