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Characterization of surface electromyography using time domain features for determining hand motion and stages of contraction

Bin Ahmad Nadzri AA, Ahmad SA, Marhaban MH, Jaafar H

Australas Phys Eng Sci Med, 2014 Mar;37(1):133-7.
PMID: 24443218 DOI: 10.1007/s13246-014-0243-3

Surface electromyography (SEMG) signals can provide important information for prosthetic hand control application. In this study, time domain (TD) features were used in extracting information from the SEMG signal in determining hand motions and stages of contraction (start, middle and end). Data were collected from ten healthy subjects. Two muscles, which are flexor carpi ulnaris (FCU) and extensor carpi radialis (ECR) were assessed during three hand motions of wrist flexion (WF), wrist extension (WE) and co-contraction (CC). The SEMG signals were first segmented into 132.5 ms windows, full wave rectified and filtered with a 6 Hz low pass Butterworth filter. Five TD features of mean absolute value, variance, root mean square, integrated absolute value and waveform length were used for feature extraction and subsequently patterns were determined. It is concluded that the TD features that were used are able to differentiate hand motions. However, for the stages of contraction determination, although there were patterns observed, it is determined that the stages could not be properly be differentiated due to the variability of signal strengths between subjects.

Matched MeSH terms: Muscle Contraction/physiology*
Fulltext Mechanomyogram for muscle function assessment: a review

Islam MA, Sundaraj K, Ahmad RB, Ahamed NU

PLoS One, 2013;8(3):e58902.
PMID: 23536834 DOI: 10.1371/journal.pone.0058902

BACKGROUND: Mechanomyography (MMG) has been extensively applied in clinical and experimental practice to examine muscle characteristics including muscle function (MF), prosthesis and/or switch control, signal processing, physiological exercise, and medical rehabilitation. Despite several existing MMG studies of MF, there has not yet been a review of these. This study aimed to determine the current status on the use of MMG in measuring the conditions of MFs.
METHODOLOGY/PRINCIPAL FINDINGS: Five electronic databases were extensively searched for potentially eligible studies published between 2003 and 2012. Two authors independently assessed selected articles using an MS-Word based form created for this review. Several domains (name of muscle, study type, sensor type, subject's types, muscle contraction, measured parameters, frequency range, hardware and software, signal processing and statistical analysis, results, applications, authors' conclusions and recommendations for future work) were extracted for further analysis. From a total of 2184 citations 119 were selected for full-text evaluation and 36 studies of MFs were identified. The systematic results find sufficient evidence that MMG may be used for assessing muscle fatigue, strength, and balance. This review also provides reason to believe that MMG may be used to examine muscle actions during movements and for monitoring muscle activities under various types of exercise paradigms.
CONCLUSIONS/SIGNIFICANCE: Overall judging from the increasing number of articles in recent years, this review reports sufficient evidence that MMG is increasingly being used in different aspects of MF. Thus, MMG may be applied as a useful tool to examine diverse conditions of muscle activity. However, the existing studies which examined MMG for MFs were confined to a small sample size of healthy population. Therefore, future work is needed to investigate MMG, in examining MFs between a sufficient number of healthy subjects and neuromuscular patients.

Matched MeSH terms: Muscle Contraction/physiology
The effects of thyroxine treatment on slow- and fast-contracting skeletal muscle contractions of the cat and their cyclic AMP level

Merican Z, Sukumaran S, Raji VL, Rajikin MH, Khalid BA

Clin Exp Pharmacol Physiol, 1992 Dec;19(12):843-6.
PMID: 1335382

1. The effects of thyroxine treatment on soleus and extensor digitorum longus (EDL) muscle contractions and their cyclic adenosine 3',5'-monophosphate (cyclic AMP) levels were examined in anaesthetized cats. 2. Thyroxine treatment decreased the tension of incomplete tetanic contractions of the soleus as well as the EDL muscles. The effect on tension of these muscles was not associated with an increase in the cyclic AMP level of the muscle as is the case with a beta 2-adrenoceptor agonist effect. 3. The results do not support the involvement of cyclic AMP in the tension depressant effect of thyroxine on contractions of skeletal muscle. 4. It is suggested that the muscle weakness and tremor observed in thyrotoxicosis and during administration of beta 2-adrenoceptor agonists are mediated by different mechanisms.

Matched MeSH terms: Muscle Contraction/drug effects*
Prostaglandin F 2 for induction of labour

Cheah SF, Khairuddin Y

Med J Malaysia, 1973 Mar;27(3):211-6.
PMID: 4268927
Matched MeSH terms: Muscle Contraction/drug effects
A demonstration of the use of the polygraph to record Schultz-Dale reactions utilizing sera of monkeys infected with Brugia malayi as sources of both antibody and antigen

Guest MF, Kek CL, Wong MM, Cheong LK

Med J Malaya, 1966 Jun;20(4):325-6.
PMID: 4224346
Matched MeSH terms: Muscle Contraction/physiology*
A systematic review of muscle activity assessment of the biceps brachii muscle using mechanomyography

Talib I, Sundaraj K, Lam CK, Sundaraj S

J Musculoskelet Neuronal Interact, 2018 12 01;18(4):446-462.
PMID: 30511949

This systematic review aims to categorically analyses the literature on the assessment of biceps brachii (BB) muscle activity through mechanomyography (MMG). The application of our search criteria to five different databases identified 319 studies. A critical review of the 48 finally selected records, revealed the diversity of protocols and parameters that are employed in MMG-based assessments of BB muscle activity. The observations were categorized into the following: muscle torque, fatigue, strength and physiology. The available information on the muscle contraction protocol, sensor(s), MMG signal parameters and obtained results were then tabulated based on these categories for further analysis. The review affirms that - 1) MMG is suitable for skeletal muscle activity assessment and can be employed potentially for further investigation of the BB muscle activity and condition (e.g., force, torque, fatigue, and contractile properties), 2) a majority of the records focused on static contractions of the BB, and the analysis of dynamic muscle contractions using MMG is thus a research gap, and 3) very few studies have focused on the analysis of BB muscle activity under externally stimulated contractions. Taken together, the findings of this review on BB activity assessment using MMG affirm the potential of MMG as an alternative tool.

Matched MeSH terms: Muscle Contraction/physiology*
Fulltext Amplitude analysis of lower leg muscle in car pedal operation in specific driving posture and duration

Khamis, N.K., Deros, B.M

Journal of Engineering and Science Research, 2018;2(3):14-19.
MyJurnal

Driving posture is important to determine the comfortability of the driver. The purpose of this study is to investigate the muscle response in car pedal operation. To evaluate this response, 11 volunteers involved in simulated driving experiment using an electrical impedance myography to detect the muscle contraction of the lower leg, particularly at Gastrocnemius medial (GM). The driver requires to perform different pedal actions. The results depict that GM muscle shows different reaction according to pedal actions. According to these results, different degree of ankle angle lead to different muscle response. These findings help us to understand the effect of physical attribute related to muscle response and joint angle on driver during monotonous driving task.

Matched MeSH terms: Muscle Contraction
Potentiation of bradykinin-induced responses by indomethacin in the intact and denuded epithelium of guinea pig tracheal preparations

Akbar A, Sharma JN, Yusof AP, Gan EK

Int J Tissue React, 1998;20(3):95-100.
PMID: 9894182

We studied the effect of indomethacin, a cyclooxygenase inhibitor, on bradykinin-induced responses in the intact and denuded epithelium of the isolated tracheal smooth muscle in guinea pigs. Epithelium removal alone did not alter the responsiveness to bradykinin. Indomethacin (2.8 microM) enhanced the sensitivity to bradykinin of both intact and denuded preparations. This finding suggests that the tracheal epithelial may have no protective effect on the contractile responses induced by bradykinin. This may be due to the presence of high amounts of bradykinin-inactivating enzymes in the tracheal smooth muscle. Indomethacin-medicated potentiation caused by bradykinin in epithelium intact and denuded preparations may be an indication of removal of the bronchodilator prostaglandin biosynthesis. The significance of these findings is discussed.

Matched MeSH terms: Muscle Contraction/drug effects*; Muscle Contraction/physiology
Fulltext Vaginismus and subfertility: case reports on the association observed in clinical practice

Ramli M, Nora M, Roszaman R, Hatta S

Malays Fam Physician, 2012;7(1):24-7.
PMID: 25606241 MyJurnal

OBJECTIVE: To analyse the features of patients with vaginismus first presented to a gynaecologist for infertility before being referred for psychiatric evaluation and management. The case series aim to provide some insight on features and presentations of Asian women with vaginismus. Vaginismus is characterised by persistent or recurrent difficulties in vaginal penetration despite the woman's wish for coitus. Avoidance, phobia, anticipatory fear of pain and involuntary pelvic muscle contraction are the most common symptoms.

METHOD: We report a series of cases of Malaysian women who had been suffering from vaginismus and 'infertility'. All the cases had never been attended to medically and there were long delays in seeking intervention. There was no history of traumatic sexual experience or any major psychiatric illness in these patients. Majority of the patients had prominent symptoms of anxiety.

CONCLUSION: The cases illustrate that it is important to rule out the possibility of vaginismus among patients with infertility. The former have unique psychological features which require psychological interventions.

Matched MeSH terms: Muscle Contraction
Fulltext Estimation of Electrically-Evoked Knee Torque from Mechanomyography Using Support Vector Regression

Ibitoye MO, Hamzaid NA, Abdul Wahab AK, Hasnan N, Olatunji SO, Davis GM

Sensors (Basel), 2016 Jul 19;16(7).
PMID: 27447638 DOI: 10.3390/s16071115

The difficulty of real-time muscle force or joint torque estimation during neuromuscular electrical stimulation (NMES) in physical therapy and exercise science has motivated recent research interest in torque estimation from other muscle characteristics. This study investigated the accuracy of a computational intelligence technique for estimating NMES-evoked knee extension torque based on the Mechanomyographic signals (MMG) of contracting muscles that were recorded from eight healthy males. Simulation of the knee torque was modelled via Support Vector Regression (SVR) due to its good generalization ability in related fields. Inputs to the proposed model were MMG amplitude characteristics, the level of electrical stimulation or contraction intensity, and knee angle. Gaussian kernel function, as well as its optimal parameters were identified with the best performance measure and were applied as the SVR kernel function to build an effective knee torque estimation model. To train and test the model, the data were partitioned into training (70%) and testing (30%) subsets, respectively. The SVR estimation accuracy, based on the coefficient of determination (R²) between the actual and the estimated torque values was up to 94% and 89% during the training and testing cases, with root mean square errors (RMSE) of 9.48 and 12.95, respectively. The knee torque estimations obtained using SVR modelling agreed well with the experimental data from an isokinetic dynamometer. These findings support the realization of a closed-loop NMES system for functional tasks using MMG as the feedback signal source and an SVR algorithm for joint torque estimation.

Matched MeSH terms: Muscle Contraction
Fatigue effect on cross-talk in mechanomyography signals of extensor and flexor forearm muscles during maximal voluntary isometric contractions

Mohamad Ismail MR, Lam CK, Sundaraj K, Rahiman MHF

J Musculoskelet Neuronal Interact, 2021 12 01;21(4):481-494.
PMID: 34854387

OBJECTIVE: This paper presents the analyses of the fatigue effect on the cross-talk in mechanomyography (MMG) signals of extensor and flexor forearm muscles during pre- and post-fatigue maximum voluntary isometric contraction (MVIC).
METHODS: Twenty male participants performed repetitive submaximal (60% MVIC) grip muscle contractions to induce muscle fatigue and the results were analyzed during the pre- and post-fatigue MVIC. MMG signals were recorded on the extensor digitorum (ED), extensor carpi radialis longus (ECRL), flexor digitorum superficialis (FDS) and flexor carpi radialis (FCR) muscles. The cross-correlation coefficient was used to quantify the cross-talk values in forearm muscle pairs (MP1, MP2, MP3, MP4, MP5 and MP6). In addition, the MMG RMS and MMG MPF were calculated to determine force production and muscle fatigue level, respectively.
RESULTS: The fatigue effect significantly increased the cross-talk values in forearm muscle pairs except for MP2 and MP6. While the MMG RMS and MMG MPF significantly decreased (p<0.05) based on the examination of the mean differences from pre- and post-fatigue MVIC.
CONCLUSION: The presented results can be used as a reference for further investigation of cross-talk on the fatigue assessment of extensor and flexor muscles' mechanic.

Matched MeSH terms: Muscle Contraction
Fulltext Mechanomyography and Torque during FES-Evoked Muscle Contractions to Fatigue in Individuals with Spinal Cord Injury

Mohamad NZ, Hamzaid NA, Davis GM, Abdul Wahab AK, Hasnan N

Sensors (Basel), 2017 Jul 14;17(7).
PMID: 28708068 DOI: 10.3390/s17071627

A mechanomyography muscle contraction (MC) sensor, affixed to the skin surface, was used to quantify muscle tension during repetitive functional electrical stimulation (FES)-evoked isometric rectus femoris contractions to fatigue in individuals with spinal cord injury (SCI). Nine persons with motor complete SCI were seated on a commercial muscle dynamometer that quantified peak torque and average torque outputs, while measurements from the MC sensor were simultaneously recorded. MC-sensor-predicted measures of dynamometer torques, including the signal peak (SP) and signal average (SA), were highly associated with isometric knee extension peak torque (SP: r = 0.91, p < 0.0001), and average torque (SA: r = 0.89, p < 0.0001), respectively. Bland-Altman (BA) analyses with Lin's concordance (ρC) revealed good association between MC-sensor-predicted peak muscle torques (SP; ρC = 0.91) and average muscle torques (SA; ρC = 0.89) with the equivalent dynamometer measures, over a range of FES current amplitudes. The relationship of dynamometer torques and predicted MC torques during repetitive FES-evoked muscle contraction to fatigue were moderately associated (SP: r = 0.80, p < 0.0001; SA: r = 0.77; p < 0.0001), with BA associations between the two devices fair-moderate (SP; ρC = 0.70: SA; ρC = 0.30). These findings demonstrated that a skin-surface muscle mechanomyography sensor was an accurate proxy for electrically-evoked muscle contraction torques when directly measured during isometric dynamometry in individuals with SCI. The novel application of the MC sensor during FES-evoked muscle contractions suggested its possible application for real-world tasks (e.g., prolonged sit-to-stand, stepping,) where muscle forces during fatiguing activities cannot be directly measured.

Matched MeSH terms: Muscle Contraction
Fulltext Mechanomyographic parameter extraction methods: an appraisal for clinical applications

Ibitoye MO, Hamzaid NA, Zuniga JM, Hasnan N, Wahab AK

Sensors (Basel), 2014;14(12):22940-70.
PMID: 25479326 DOI: 10.3390/s141222940

The research conducted in the last three decades has collectively demonstrated that the skeletal muscle performance can be alternatively assessed by mechanomyographic signal (MMG) parameters. Indices of muscle performance, not limited to force, power, work, endurance and the related physiological processes underlying muscle activities during contraction have been evaluated in the light of the signal features. As a non-stationary signal that reflects several distinctive patterns of muscle actions, the illustrations obtained from the literature support the reliability of MMG in the analysis of muscles under voluntary and stimulus evoked contractions. An appraisal of the standard practice including the measurement theories of the methods used to extract parameters of the signal is vital to the application of the signal during experimental and clinical practices, especially in areas where electromyograms are contraindicated or have limited application. As we highlight the underpinning technical guidelines and domains where each method is well-suited, the limitations of the methods are also presented to position the state of the art in MMG parameters extraction, thus providing the theoretical framework for improvement on the current practices to widen the opportunity for new insights and discoveries. Since the signal modality has not been widely deployed due partly to the limited information extractable from the signals when compared with other classical techniques used to assess muscle performance, this survey is particularly relevant to the projected future of MMG applications in the realm of musculoskeletal assessments and in the real time detection of muscle activity.

Matched MeSH terms: Muscle Contraction*
Role of nitric oxide in skeletal muscle glucose uptake during exercise

Hong YH, Betik AC, McConell GK

Exp Physiol, 2014 Dec 1;99(12):1569-73.
PMID: 25192731 DOI: 10.1113/expphysiol.2014.079202

Nitric oxide is produced within skeletal muscle fibres and has various functions in skeletal muscle. There is evidence that NO may be essential for normal increases in skeletal muscle glucose uptake during contraction/exercise. Although there have been some discrepant results, it has been consistently demonstrated that inhibition of NO synthase (NOS) attenuates the increase in skeletal muscle glucose uptake during contraction in mouse and rat muscle ex vivo, during in situ contraction in rats and during exercise in humans. The NO-mediated increase in skeletal muscle glucose uptake during contraction/exercise is probably due to the modulation of intramuscular signalling that ultimately increases glucose transporter 4 (GLUT4) translocation and is, surprisingly, independent of blood flow. In this review, we discuss the evidence for and against a role of NO in regulating skeletal muscle glucose uptake during contraction/exercise and outline the possible mechanism(s) involved. Emerging findings regarding the role of neuronal NOS mu (nNOSμ) in this process are also discussed.

Matched MeSH terms: Muscle Contraction/physiology*
Fulltext Effect of noni (Morinda citrifolia Linn.) fruit and its bioactive principles scopoletin and rutin on rat vas deferens contractility: an ex vivo study

Pandy V, Narasingam M, Kunasegaran T, Murugan DD, Mohamed Z

ScientificWorldJournal, 2014;2014:909586.
PMID: 25045753 DOI: 10.1155/2014/909586

This study examined the effect of methanolic extract of Morinda citrifolia Linn. (MMC) and its bioactive principles, scopoletin and rutin, on dopamine- and noradrenaline-evoked contractility in isolated rat vas deferens preparations. MMC (1-40 mg/mL), scopoletin (1-200 μg/mL), and rutin hydrate (0.6-312.6 μg/mL) dose-dependently inhibited the contractility evoked by submaximal concentrations of both dopamine and noradrenaline, respectively. Haloperidol and prazosin, reference dopamine D2, and α 1-adrenoceptors antagonists significantly reversed the dopamine- and noradrenaline-induced contractions, respectively, in a dose-dependent manner. Interestingly, MMC per se at higher doses (60-100 mg/mL) showed dose-dependent contractile response in rat vas deferens which was partially inhibited by high doses of haloperidol but not by prazosin. These results demonstrated the biphasic effects of MMC on dopaminergic system; that is, antidopaminergic effect at lower concentrations (<40 mg/mL) and dopaminergic agonistic effect at higher concentrations (>60 mg/mL). However, similar contractile response at high doses of scopoletin (0.5-5 mg/mL) and rutin hydrate (0.5-5 mg/mL) per se was not observed. Therefore, it can be concluded that the bioactive principles of MMC, scopoletin, and rutin might be responsible for the antidopaminergic and antiadrenergic activities of MMC.

Matched MeSH terms: Muscle Contraction/drug effects*
Analysis of crosstalk in the mechanomyographic signals generated by forearm muscles during different wrist postures

Islam A, Sundaraj K, Ahmad RB, Sundaraj S, Ahamed NU, Ali MA

Muscle Nerve, 2015 Jun;51(6):899-906.
PMID: 25204740 DOI: 10.1002/mus.24454

In this study, we analyzed the crosstalk in mechanomyographic (MMG) signals generated by the extensor digitorum (ED), extensor carpi ulnaris (ECU), and flexor carpi ulnaris (FCU) muscles of the forearm during wrist flexion (WF) and extension (WE) and radial (RD) and ulnar (UD) deviations.

Matched MeSH terms: Muscle Contraction/physiology*
Fulltext The effectiveness of FES-evoked EMG potentials to assess muscle force and fatigue in individuals with spinal cord injury

Ibitoye MO, Estigoni EH, Hamzaid NA, Wahab AK, Davis GM

Sensors (Basel), 2014;14(7):12598-622.
PMID: 25025551 DOI: 10.3390/s140712598

The evoked electromyographic signal (eEMG) potential is the standard index used to monitor both electrical changes within the motor unit during muscular activity and the electrical patterns during evoked contraction. However, technical and physiological limitations often preclude the acquisition and analysis of the signal especially during functional electrical stimulation (FES)-evoked contractions. Hence, an accurate quantification of the relationship between the eEMG potential and FES-evoked muscle response remains elusive and continues to attract the attention of researchers due to its potential application in the fields of biomechanics, muscle physiology, and rehabilitation science. We conducted a systematic review to examine the effectiveness of eEMG potentials to assess muscle force and fatigue, particularly as a biofeedback descriptor of FES-evoked contractions in individuals with spinal cord injury. At the outset, 2867 citations were identified and, finally, fifty-nine trials met the inclusion criteria. Four hypotheses were proposed and evaluated to inform this review. The results showed that eEMG is effective at quantifying muscle force and fatigue during isometric contraction, but may not be effective during dynamic contractions including cycling and stepping. Positive correlation of up to r = 0.90 (p < 0.05) between the decline in the peak-to-peak amplitude of the eEMG and the decline in the force output during fatiguing isometric contractions has been reported. In the available prediction models, the performance index of the eEMG signal to estimate the generated muscle force ranged from 3.8% to 34% for 18 s to 70 s ahead of the actual muscle force generation. The strength and inherent limitations of the eEMG signal to assess muscle force and fatigue were evident from our findings with implications in clinical management of spinal cord injury (SCI) population.

Matched MeSH terms: Muscle Contraction*
Evaluation of repetitive isometric contractions on the heads of triceps brachii muscle during grip force exercise

Ali MA, Sundaraj K, Ahmad RB, Ahamed NU, Islam MA, Sundaraj S

Technol Health Care, 2014;22(4):617-25.
PMID: 24990168 DOI: 10.3233/THC-140833

Normally, surface electromyography electrodes are used to evaluate the activity of superficial muscles during various kinds of voluntary contractions of muscle fiber. The objective of the present study was to investigate the effect of repetitive isometric contractions on the three heads of the triceps brachii muscle during handgrip force exercise.

Matched MeSH terms: Muscle Contraction/physiology*
Mechanomyography and muscle function assessment: a review of current state and prospects

Ibitoye MO, Hamzaid NA, Zuniga JM, Abdul Wahab AK

Clin Biomech (Bristol, Avon), 2014 Jun;29(6):691-704.
PMID: 24856875 DOI: 10.1016/j.clinbiomech.2014.04.003

Previous studies have explored to saturation the efficacy of the conventional signal (such as electromyogram) for muscle function assessment and found its clinical impact limited. Increasing demand for reliable muscle function assessment modalities continues to prompt further investigation into other complementary alternatives. Application of mechanomyographic signal to quantify muscle performance has been proposed due to its inherent mechanical nature and ability to assess muscle function non-invasively while preserving muscular neurophysiologic information. Mechanomyogram is gaining accelerated applications in evaluating the properties of muscle under voluntary and evoked muscle contraction with prospects in clinical practices. As a complementary modality and the mechanical counterpart to electromyogram; mechanomyogram has gained significant acceptance in analysis of isometric and dynamic muscle actions. Substantial studies have also documented the effectiveness of mechanomyographic signal to assess muscle performance but none involved comprehensive appraisal of the state of the art applications with highlights on the future prospect and potential integration into the clinical practices. Motivated by the dearth of such critical review, we assessed the literature to investigate its principle of acquisition, current applications, challenges and future directions. Based on our findings, the importance of rigorous scientific and clinical validation of the signal is highlighted. It is also evident that as a robust complement to electromyogram, mechanomyographic signal may possess unprecedented potentials and further investigation will be enlightening.

Matched MeSH terms: Muscle Contraction/physiology*
Does performing drop jumps with additional eccentric loading improve jump performance?

Aboodarda SJ, Byrne JM, Samson M, Wilson BD, Mokhtar AH, Behm DG

J Strength Cond Res, 2014 Aug;28(8):2314-23.
PMID: 24796986 DOI: 10.1519/JSC.0000000000000498

Previous investigators have speculated that applying additional external load throughout the eccentric phase of the jumping movement could amplify the stretch-shortening cycle mechanism and modulate jumping performance and jump exercise intensity. The aims of this study, therefore, were to determine the effect of increased eccentric phase loading, as delivered using an elastic device, on drop jumps (DJs) performed from different drop heights. Of specific interest were changes in (a) the kinetics; eccentric and concentric impulse, rate of force development (RFD), concentric velocity and (b) the electromyographic (EMG) activity of leg muscles. In a randomized repeated-measure study, 15 highly resistance trained male subjects performed DJs from 3 heights (20, 35, and 50 cm) under 3 different conditions: body weight only (free DJ) and with elastic bands providing downward force equivalent to 20% (+20% DJ) and 30% (+30% DJ) of body mass. All DJs were recorded using video and force plate data that were synchronized with EMG data. Results demonstrated that using additional tensile load during the airborne and eccentric phases of the DJ could enhance eccentric impulse (p = 0.042) and RFD (p < 0.001) and resulted in small to moderate effect size (ES) increases in quadriceps intergrated EMG across the eccentric phase (0.23 > ES > 0.51). The observed greater eccentric loading, however, did not immediately alter concentric kinetics and jump height nor did it alter muscle activation levels during this phase. The findings indicated that, in addition to the conventional technique of increasing drop height, using a tensile load during the airborne and eccentric phases of the DJ could further improve eccentric loading of DJs. As it has been suggested that eccentric impulse and RFD are indicators of DJ exercise intensity, these findings suggest that the loaded DJs, using additional elastic load, may be an effective technique for improving DJ exercise intensity without acute effects on the jumping performance and neuromuscular activation level in highly trained athletes.

Matched MeSH terms: Muscle Contraction/physiology*

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