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Archives of Physical Medicine and... Mar 2023To investigate (1) how current and pulse frequency of electrical stimulation (ES) as well as contraction mode (isometric, concentric, and eccentric) influence torque...
OBJECTIVE
To investigate (1) how current and pulse frequency of electrical stimulation (ES) as well as contraction mode (isometric, concentric, and eccentric) influence torque output and discomfort and (2) how familiarization by repeated ES sessions influences ratings of perceived discomfort.
DESIGN
An experimental study, 3 sessions.
SETTING
A university laboratory.
PARTICIPANTS
Eight healthy participants (5 men, 3 women; mean age 25.2 years; N=8).
INTERVENTIONS
Participants completed 3 trial days, each including 17 electrically evoked thigh muscle contractions. On each trial day, the first 6 contractions consisted of 2 isometric, 2 concentric, and 2 eccentric muscle contractions randomly ordered with a fixed stimulation current and pulse frequency (200 mA, 20 Hz), while the remaining 11 muscle contractions were all isometric with randomly ordered combinations of current (100-250 mA) and pulse frequency (20-100 Hz).
MAIN OUTCOME MEASURES
Torque and perceived discomfort were measured for each ES-evoked contraction.
RESULTS
Overall, the findings revealed that a higher stimulation frequency was associated with an increased torque without increased discomfort, while higher currents were associated with increases of both torque and discomfort. Contraction type did not influence level of discomfort, despite eccentric contractions eliciting higher torque compared with concentric and isometric contractions (P<.001). Finally, a significant familiarization to ES (P<.001) was observed after just 1 of 3 identical stimulation sessions.
CONCLUSIONS
The outlined data suggest that to elicit high torque levels while minimizing levels of discomfort in young subjects, eccentric muscle contractions evoked with a low stimulation current, and a high pulse frequency are preferable. Furthermore, a single familiarization session significantly lowers rating of perceived discomfort during ES.
Topics: Male; Humans; Female; Young Adult; Adult; Torque; Muscle Contraction; Muscle, Skeletal; Isometric Contraction; Electric Stimulation
PubMed: 36167118
DOI: 10.1016/j.apmr.2022.09.004 -
Sensors (Basel, Switzerland) Sep 2023This study explores the development and validation of a low-cost electromyography (EMG) device for monitoring muscle activity and muscle fatigue by monitoring the key...
This study explores the development and validation of a low-cost electromyography (EMG) device for monitoring muscle activity and muscle fatigue by monitoring the key features in EMG time and frequency domains. The device consists of a Raspberry Pico microcontroller interfacing a Myoware EMG module. The experiment involved 34 volunteers (14 women, 20 men) who performed isometric and isotonic contractions using a hand dynamometer. The low-cost EMG device was compared to a research-grade EMG device, recording EMG signals simultaneously. Key features including root mean square (RMS), median power frequency (MDF), and mean power frequency (MNF) were extracted to evaluate muscle fatigue. During isometric contraction, a strong congruence between the two devices, with similar readings and behavior of the extracted features, was observed, and the Wilcoxon signed rank test confirmed no significant difference in the ability to detect muscle fatigue between the devices. For isotonic contractions, the low-cost device demonstrated behavior similar to the professional EMG device in 70.58% of cases, despite some susceptibility to noise and movement. This suggests the potential viability of the low-cost EMG device as a portable tool for assessing muscle fatigue, enabling accessible and cost-effective management of muscle health in various work scenarios.
Topics: Male; Humans; Female; Electromyography; Muscle, Skeletal; Muscle Fatigue; Isometric Contraction; Movement; Muscle Contraction
PubMed: 37765930
DOI: 10.3390/s23187873 -
European Journal of Applied Physiology Jun 2023A single bout of foam rolling (FR) can acutely increase joint range of motion (ROM) without detrimental effects on subsequent muscle performance. Similarly, long-term FR... (Review)
Review
A single bout of foam rolling (FR) can acutely increase joint range of motion (ROM) without detrimental effects on subsequent muscle performance. Similarly, long-term FR training can increase ROM, while muscle performance seems to be unaffected. Although the acute and long-term effects of FR on the treated muscle are understood, the impact of FR on the contralateral side is not well known. Therefore, this scoping review aims to summarize the current evidence on the acute and long-term effect of FR on the ipsilateral limb on ROM and muscle performance (i.e., maximum force, rate of force development, jump height) for the contralateral (non-treated) limb. Potential explanatory mechanisms are also discussed. There is evidence that a single bout of FR on the ipsilateral limb increases ROM of the contralateral limb; however, evidence is limited for long-term effects. The most likely mechanism for contralateral ROM increases is a reduced perception of pain. With regard to isolated muscle contractions, no changes in muscle performance (i.e., maximum voluntary isometric contraction, maximum voluntary dynamic contraction) were found in the contralateral limb after a single bout of FR on the ipsilateral limb. Notably, only one study reported large impairments in rate of force development of the contralateral limb following FR on the ipsilateral leg, possibly due to decreased motor unit recruitment. Furthermore, to date there are only two studies examining the long-term FR training of the ipsilateral limb on performance (i.e., maximal strength and jump performance) which reported moderate improvements. Although, trivial to very large changes on a variety of parameters were found in this study, the functional and practical relevance of our findings should be interpreted with caution.
Topics: Humans; Muscle, Skeletal; Muscle Contraction; Isometric Contraction; Range of Motion, Articular; Extremities
PubMed: 36694004
DOI: 10.1007/s00421-023-05142-2 -
PloS One 2022In human applied physiology studies, the amplitude of recorded muscle electromyographic activity (EMG) is often normalized to maximal EMG recorded during a maximal...
In human applied physiology studies, the amplitude of recorded muscle electromyographic activity (EMG) is often normalized to maximal EMG recorded during a maximal voluntary contraction. When maximal contractions cannot be reliably obtained (e.g. in people with muscle paralysis, anterior cruciate ligament injury, or arthritis), EMG is sometimes normalized to the maximal compound muscle action potiential evoked by stimulation, the Mmax. However, it is not known how these two methods of normalization affect the conclusions and comparability of studies. To address this limitation, we investigated the relationship between voluntary muscle activation and EMG normalized either to maximal EMG or to Mmax. Twenty-five able-bodied adults performed voluntary isometric ankle plantarflexion contractions to a range of percentages of maximal voluntary torque. Ankle torque, plantarflexor muscle EMG, and voluntary muscle activation measured by twitch interpolation were recorded. EMG recorded at each contraction intensity was normalized to maximal EMG or to Mmax for each plantarflexor muscle, and the relationship between the two normalization approaches quantified. A slope >1 indicated EMG amplitude normalized to maximal EMG (vertical axis) was greater than EMG normalized to Mmax (horizontal axis). Mean estimates of the slopes were large and had moderate precision: soleus 8.7 (95% CI 6.9 to 11.0), medial gastrocnemius 13.4 (10.5 to 17.0), lateral gastrocnemius 11.4 (9.4 to 14.0). This indicates EMG normalized to Mmax is approximately eleven times smaller than EMG normalized to maximal EMG. Normalization to maximal EMG gave closer approximations to the level of voluntary muscle activation assessed by twitch interpolation.
Topics: Adult; Humans; Electromyography; Muscle Contraction; Isometric Contraction; Torque; Muscle, Skeletal
PubMed: 36409688
DOI: 10.1371/journal.pone.0277947 -
BioMed Research International 2016The aim of the study was to determine the effect of different muscle length and visual feedback information (VFI) on accuracy of isometric contraction of elbow flexors...
UNLABELLED
The aim of the study was to determine the effect of different muscle length and visual feedback information (VFI) on accuracy of isometric contraction of elbow flexors in men after an ischemic stroke (IS).
MATERIALS AND METHODS
Maximum voluntary muscle contraction force (MVMCF) and accurate determinate muscle force (20% of MVMCF) developed during an isometric contraction of elbow flexors in 90° and 60° of elbow flexion were measured by an isokinetic dynamometer in healthy subjects (MH, n = 20) and subjects after an IS during their postrehabilitation period (MS, n = 20).
RESULTS
In order to evaluate the accuracy of the isometric contraction of the elbow flexors absolute errors were calculated. The absolute errors provided information about the difference between determinate and achieved muscle force.
CONCLUSIONS
There is a tendency that greater absolute errors generating determinate force are made by MH and MS subjects in case of a greater elbow flexors length despite presence of VFI. Absolute errors also increase in both groups in case of a greater elbow flexors length without VFI. MS subjects make greater absolute errors generating determinate force without VFI in comparison with MH in shorter elbow flexors length.
Topics: Elbow; Humans; Isometric Contraction; Male; Middle Aged; Muscle Contraction; Muscle, Skeletal; Range of Motion, Articular; Stroke
PubMed: 27042670
DOI: 10.1155/2016/7641705 -
The Journal of Physiology Jul 2009In striated muscle, activation of contraction is initiated by membrane depolarisation caused by an action potential, which triggers the release of Ca(2+) stored in the... (Review)
Review
In striated muscle, activation of contraction is initiated by membrane depolarisation caused by an action potential, which triggers the release of Ca(2+) stored in the sarcoplasmic reticulum by a process called excitation-contraction coupling. Excitation-contraction coupling occurs via a highly sophisticated supramolecular signalling complex at the junction between the sarcoplasmic reticulum and the transverse tubules. It is generally accepted that the core components of the excitation-contraction coupling machinery are the dihydropyridine receptors, ryanodine receptors and calsequestrin, which serve as voltage sensor, Ca(2+) release channel, and Ca(2+) storage protein, respectively. Nevertheless, a number of additional proteins have been shown to be essential both for the structural formation of the machinery involved in excitation-contraction coupling and for its fine tuning. In this review we discuss the functional role of minor sarcoplasmic reticulum protein components. The definition of their roles in excitation-contraction coupling is important in order to understand how mutations in genes involved in Ca(2+) signalling cause neuromuscular disorders.
Topics: Animals; Calcium Signaling; Humans; Models, Biological; Muscle Contraction; Muscle Proteins; Muscle, Skeletal; Sarcoplasmic Reticulum
PubMed: 19403606
DOI: 10.1113/jphysiol.2009.171876 -
FEBS Letters Jun 1993Recent experimental findings suggest that the myosin cross-bridge theory may no longer be adequate to account for certain basic facts concerning muscle contraction. A... (Review)
Review
Recent experimental findings suggest that the myosin cross-bridge theory may no longer be adequate to account for certain basic facts concerning muscle contraction. A newly-proposed mechanism based on length changes in actin filaments might be the basis for a simpler explanation for how the free energy of ATP hydrolysis can be transduced into work by muscle fibers.
Topics: Actins; Adenosine Triphosphatases; Models, Biological; Muscle Contraction; Muscles
PubMed: 8513893
DOI: 10.1016/0014-5793(93)81413-t -
Journal of Musculoskeletal & Neuronal... Sep 2022This study evaluates the effect of post-activation potentiation (PAP) after 5x5s maximal voluntary isometric contractions (activation stimulus, AS) on tensiomyography...
OBJECTIVES
This study evaluates the effect of post-activation potentiation (PAP) after 5x5s maximal voluntary isometric contractions (activation stimulus, AS) on tensiomyography (TMG) and torque twitch contractile parameters of vastus lateralis (VL) and medialis (VM), respectively. Further, we validated the decomposition of TMG response to separate responses of three fiber types.
METHODS
15 healthy individuals participated in this study (40% women; age 19±2.3 years). A decomposition of VL TMG response was done after optimal fitting of three exponential curves.
RESULTS
We found main effects in contraction time (Tc) for muscle, method and time. Furthermore, we found interactions between muscle*method, method*time and muscle*method*time. Compared to PRE AS, we found shorter TMG Tc in VL and VM during the first two minutes after AS. Torque Tc remained unchanged in VL, while it increased in VM within 30 seconds after AS. A decomposition of VL TMG response confirmed PAP effects being present only in decomposed type IIb muscle fibers.
CONCLUSION
The TMG is a sensitive method to detect PAP effects with a sensor mounted directly above the muscle belly. After the decomposition of the TMG signal to three separate muscle fiber phenotypes, we provided a non-invasive insight in the contribution of each muscle fiber phenotype to the PAP of the whole muscle.
Topics: Electromyography; Female; Humans; Isometric Contraction; Male; Muscle Contraction; Muscle, Skeletal; Torque
PubMed: 36046987
DOI: No ID Found -
Journal of Applied Physiology... Dec 2022The study analyzed neural mechanisms mediating spinal excitability modulation during eccentric (ECC) movement (passive muscle lengthening, submaximal, and maximal ECC...
The study analyzed neural mechanisms mediating spinal excitability modulation during eccentric (ECC) movement (passive muscle lengthening, submaximal, and maximal ECC contractions) as compared with concentric (CON) conditions. Twenty-two healthy subjects participated in three experiments. ( = 13) examined D presynaptic inhibition (D PI) and recurrent inhibition (RI) modulation during passive muscle lengthening and shortening, by conditioning the soleus (SOL) H-reflex with common peroneal nerve submaximal and tibial nerve maximal stimulation, respectively. ( = 13) analyzed the effect of passive muscle lengthening on D PI and heteronymous Ia facilitation (HF, conditioning the SOL H-reflex by femoral stimulation). ( = 13) focused on the effect of muscle contraction level (20%, 50%, and 100% of maximal voluntary contraction) on D PI and RI. Results showed a significantly higher level of D PI during passive muscle lengthening than shortening ( < 0.01), whereas RI and HF were not affected by passive muscle movement. D PI and RI were both higher during ECC as compared with CON contractions ( < 0.001). However, the amount of D PI was independent of the torque level, whereas RI was reduced as the torque level increased ( < 0.05). The decreased spinal excitability induced by muscle lengthening during both passive and active conditions is mainly attributed to D PI, whereas RI also plays a role in the control of the specific motoneuron output during ECC contractions. Both inhibitory mechanisms are centrally controlled, but the fact that they evolve differently with torque increases, suggests a distinct supraspinal control. Presynaptic (PI) and recurrent inhibitions (RI) were studied during passive muscle lengthening and eccentric contractions. Results indicate that the increased PI during passive muscle lengthening accounts for the decreased spinal excitability at rest. During eccentric contraction both mechanisms contribute to spinal excitability modulation. The same amount of PI was observed during eccentric contractions, while RI decreased as developed torque increased. This distinct modulation according to torque level suggests a distinct supraspinal control of these mechanisms.
Topics: Humans; Electromyography; H-Reflex; Muscle, Skeletal; Muscle Contraction; Torque; Isometric Contraction
PubMed: 36356258
DOI: 10.1152/japplphysiol.00065.2022 -
Sensors (Basel, Switzerland) Apr 2016This study assessed changes in electrical impedance myography (EIM) at different levels of isometric muscle contraction as well as during exhaustive exercise at 60%...
This study assessed changes in electrical impedance myography (EIM) at different levels of isometric muscle contraction as well as during exhaustive exercise at 60% maximum voluntary contraction (MVC) until task failure. The EIM was performed on the biceps brachii muscle of 19 healthy subjects. The results showed that there was a significant difference between the muscle resistance (R) measured during the isometric contraction and when the muscle was completely relaxed. Post hoc analysis shows that the resistance increased at higher contractions (both 60% MVC and MVC), however, there were no significant changes in muscle reactance (X) during the isometric contractions. The resistance also changed during different stages of the fatigue task and there were significant decreases from the beginning of the contraction to task failure as well as between task failure and post fatigue rest. Although our results demonstrated an increase in resistance during isometric contraction, the changes were within 10% of the baseline value. These changes might be related to the modest alterations in muscle architecture during a contraction. The decrease in resistance seen with muscle fatigue may be explained by an accumulation of metabolites in the muscle tissue.
Topics: Electric Impedance; Electromyography; Humans; Isometric Contraction; Muscle Contraction; Muscle Fatigue; Muscle, Skeletal; Myography
PubMed: 27110795
DOI: 10.3390/s16040581