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  1. 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: Isometric Contraction*
  2. Li W, Hadizadeh M, Yusof A, Naharudin MN
    Sci Rep, 2024 Feb 27;14(1):4736.
    PMID: 38413632 DOI: 10.1038/s41598-024-54789-0
    The effects of IT and R.I.C.E. treatment on arm muscle performance in overhead athletes with elbow pain (EP) have been partially validated. However, there is a lack of research evidence regarding the efficacy of these two methods on arm muscle performance among swimmers with EP. The aim of this study was to investigate the trends and differences in the effects of IT and R.I.C.E. treatment on arm muscle performance among swimmers with EP. The main outcomes were the time effects and group effects of interventions on muscle voluntary contraction (MVC). Sixty elite freestyle swimmers from Tianjin, China, voluntarily participated in the study and completed a 10-week intervention program. Swimmers with EP in the IT group showed a positive trend in MVC, with an approximately 2% increase, whereas the MVC of subjects in the R.I.C.E. treatment group and control group decreased by approximately 4% and 5%, respectively. In comparison, the effects of the IT intervention on the MVC of the triceps and brachioradialis muscles in swimmers with EP were significant (p = 0.042 
    Matched MeSH terms: Isometric Contraction/physiology
  3. Hussain J, Sundaraj K, Subramaniam ID, Lam CK
    J Musculoskelet Neuronal Interact, 2019 09 01;19(3):276-285.
    PMID: 31475934
    OBJECTIVE: The objective of this study was to investigate fatigue in the three heads of the triceps brachii (TB) muscle using surface electromyography (sEMG) obtained at 30%, 45% and 60% of maximal voluntary contraction (MVC).

    METHODS: Twenty-five subjects performed isometric elbow extension until failure, and the rate of fatigue (ROF), time to fatigue (TTF) and normalized TTF (NTTF) were statistically analysed. Subsequently, the behaviour of root-mean-square (RMS), mean-power frequency (MPF) and median-power frequency (MDF) under pre-, onset- and post-fatigue conditions were compared.

    RESULTS: The findings indicated that, among the heads, ROF was statistically significant at 30% and 45% MVC (P<0.05) but TTF and NTTF at all intensities was statistically insignificant (P>0.05). For every head, only TTF was statistically significant (P<0.05) at different intensities. MPF and MDF under pre-, onset- and post-fatigue conditions were statistically significant (P<0.05) among the heads at all intensities, whereas RMS showed no such behaviour.

    CONCLUSION: The investigated parameters reveal that the three heads of TB act independently before fatigue onset and appear to work in union after fatigue. Synergist head pairs exhibit similar spectral and temporal behaviour in contrast to the non-synergist TB head pair. We find spectral parameters to be more specific predictors of fatigue.

    Matched MeSH terms: Isometric Contraction/physiology*
  4. Ahmad Naim Ismail
    Movement Health & Exercise, 2012;1(1):39-48.
    MyJurnal
    The increase in weight-lifting performance after resistance training is greater than the increase seen in maximal voluntary isometric contraction (MVC). This discrepancy has been attributed to learning and coordination. The purpose of the present study was to look into the contribution of joint angle specificity, and the specificity of the movement at various speeds in explaining the disproportionate increase in weightlifting strength compared to isometric strength. Eighteen participants completed the study. The quadriceps muscle group of each individual was trained unilaterally on a leg extension machine. Participants performed four sets of ten lifts at a steady pace. A load of 80% of the maximum load (1RM) was prescribed. The MVC of the quadriceps was measured on a strength-testing chair. The length-tension relationship was measured isometrically at 600, 750, 900, and 1050 of knee flexion. Measurement of isokinetic strength at velocities of 450/s, 1800/s and 300/s were made. All measurements were made before and after the training. The eight weeks training resulted in a 33% increased in weights lifted (p < 0.05) that was significantly greater than the gain in isometric MVC (6%). Significant gains in isometric strength were seen at all the joint angle but with no evidence of length specificity. Although there were significant gains in strength at higher velocities, they were not sufficient to explain the increased weight-lifting performance and, in any case, similar gains were seen with the untrained leg where no improvement in weight-lifting
    performance was seen. From the findings it is concluded that angle and velocity specificity could not fully account for the discrepancy between gains in weight-lifting performance compared to isometric strength.
    Matched MeSH terms: Isometric Contraction
  5. 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: Isometric Contraction
  6. 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: Isometric Contraction/physiology*
  7. Islam MA, Sundaraj K, Ahmad RB, Sundaraj S, Ahamed NU, Ali MA
    PLoS One, 2014;9(5):e96628.
    PMID: 24802858 DOI: 10.1371/journal.pone.0096628
    This study aimed: i) to examine the relationship between the magnitude of cross-talk in mechanomyographic (MMG) signals generated by the extensor digitorum (ED), extensor carpi ulnaris (ECU), and flexor carpi ulnaris (FCU) muscles with the sub-maximal to maximal isometric grip force, and with the anthropometric parameters of the forearm, and ii) to quantify the distribution of the cross-talk in the MMG signal to determine if it appears due to the signal component of intramuscular pressure waves produced by the muscle fibers geometrical changes or due to the limb tremor.
    Matched MeSH terms: Isometric Contraction/physiology*
  8. Rajikin MH
    Med J Malaysia, 1980 Sep;35(1):46-52.
    PMID: 6973059
    Seven non-anthletes [21-26 yrs] and five athletes [23-29 yrs] have participated in the study of cardiovascular and metabolic responses to 15 minutes isometric leg exercise at 15% of each of their maximal voluntary contraction force [MVC]. Oxygen consumption [V02 ]. heart rate [HR] and blood pressure (BP]. were measured during resting. exercise and recovery! periods. The results show that there were a significant increase in V02. HR and BP of the two groups studied during exercise, but no significant difference between groups has been found. This study indicates that although cardiovascular response between the rwo groups was not significantly different, 15 minutes isometric leg exercise at 15% MVC has challenged this system in a such a way to fulfill the metabolic requirement of the
    working muscle ill both groups. This finding was
    discussed in light of the available literatures.
    Matched MeSH terms: Isometric Contraction*
  9. Loh PY, Hayashi K, Nasir N, Muraki S
    J Mot Behav, 2020;52(5):634-642.
    PMID: 31571525 DOI: 10.1080/00222895.2019.1670128
    This study investigated the muscle activity and force variability in response to perturbation of assistive force during isometric elbow flexion. Sixteen healthy right-handed young men (age: 22.0 ± 1.1 years; height: 171.9 ± 4.8 cm; weight 68.4 ± 11.2 kg) were recruited and the muscle activity of biceps brachii and triceps brachii were assessed using surface electromyography. Workload force and assistive force applied on isometric elbow flexion significantly affected the changes in both biceps and triceps muscle activities. A higher assistive force was shown to result in reduced biceps muscle activity compared to the unassisted period. In contrast, the efficiency of the assistive force acting on the biceps decreased as the assistive force increased. In general, the force variability of the biceps muscle remained approximately the same at lower workload force conditions than that at higher workload force conditions. In conclusion, higher assistive force may not yield a higher performance efficiency in human-assistive force interaction.
    Matched MeSH terms: Isometric Contraction/physiology*
  10. Talib I, Sundaraj K, Lam CK
    J Musculoskelet Neuronal Interact, 2020 06 01;20(2):194-205.
    PMID: 32481235
    OBJECTIVE: To analyse the influence of muscle fibre axis on the degree of crosstalk in mechanomyographic (MMG) signals during sustained isometric forearm flexion, pronation and supination exercises performed at 80% maximum voluntary contraction (MVC) at an elbow joint angle of 90°.

    METHODS: MMG signals in longitudinal, lateral and transverse directions of muscle fibres were recorded from the elbow flexors of twenty-five male subjects using triaxial accelerometers. Cross-correlation coefficients were used to quantify the degree of crosstalk in all nine possible pairs of fibre axes, all muscle pairs and all exercises.

    RESULTS: MMG root mean square (RMS) was statistically significant among the fibre axes (p<0.05, η2=0.17- 0.34) except for biceps brachii and brachioradialis in supination and brachialis in flexion. Overall mean crosstalk values in the three muscle pairs (biceps brachii & brachialis, brachialis & brachioradialis and brachioradialis & biceps brachii) were found to be 6.09-52.17%, 4.01-61.42% and 2.16-51.85%, respectively. Crosstalk values showed statistical significance among all nine axes pairs (p<0.05, η2=0.16-0.51) except for biceps brachii & brachialis during pronation. The transverse axes pair generated the lowest mean crosstalk values (2.16-9.14%).

    CONCLUSION: MMG signals recorded using accelerometers from the transverse axes of muscle fibres in the elbow flexors are unique and yield the least amount of crosstalk.

    Matched MeSH terms: Isometric Contraction/physiology*
  11. Ibitoye MO, Hamzaid NA, Hasnan N, Abdul Wahab AK, Islam MA, Kean VS, et al.
    Med Eng Phys, 2016 Aug;38(8):767-75.
    PMID: 27289541 DOI: 10.1016/j.medengphy.2016.05.012
    The interaction between muscle contractions and joint loading produces torques necessary for movements during activities of daily living. However, during neuromuscular electrical stimulation (NMES)-evoked contractions in persons with spinal cord injury (SCI), a simple and reliable proxy of torque at the muscle level has been minimally investigated. Thus, the purpose of this study was to investigate the relationships between muscle mechanomyographic (MMG) characteristics and NMES-evoked isometric quadriceps torques in persons with motor complete SCI. Six SCI participants with lesion levels below C4 [(mean (SD) age, 39.2 (7.9) year; stature, 1.71 (0.05) m; and body mass, 69.3 (12.9) kg)] performed randomly ordered NMES-evoked isometric leg muscle contractions at 30°, 60° and 90° knee flexion angles on an isokinetic dynamometer. MMG signals were detected by an accelerometer-based vibromyographic sensor placed over the belly of rectus femoris muscle. The relationship between MMG root mean square (MMG-RMS) and NMES-evoked torque revealed a very high association (R(2)=0.91 at 30°; R(2)=0.98 at 60°; and R(2)=0.97 at 90° knee angles; P<0.001). MMG peak-to-peak (MMG-PTP) and stimulation intensity were less well related (R(2)=0.63 at 30°; R(2)=0.67 at 60°; and R(2)=0.45 at 90° knee angles), although were still significantly associated (P≤0.006). Test-retest interclass correlation coefficients (ICC) for the dependent variables ranged from 0.82 to 0.97 for NMES-evoked torque, between 0.65 and 0.79 for MMG-RMS, and from 0.67 to 0.73 for MMG-PTP. Their standard error of measurements (SEM) ranged between 10.1% and 31.6% (of mean values) for torque, MMG-RMS and MMG-PTP. The MMG peak frequency (MMG-PF) of 30Hz approximated the stimulation frequency, indicating NMES-evoked motor unit firing rate. The results demonstrated knee angle differences in the MMG-RMS versus NMES-isometric torque relationship, but a similar torque related pattern for MMG-PF. These findings suggested that MMG was well associated with torque production, reliably tracking the motor unit recruitment pattern during NMES-evoked muscle contractions. The strong positive relationship between MMG signal and NMES-evoked torque production suggested that the MMG might be deployed as a direct proxy for muscle torque or fatigue measurement during leg exercise and functional movements in the SCI population.
    Matched MeSH terms: Isometric Contraction*
  12. Nazmi N, Abdul Rahman MA, Yamamoto S, Ahmad SA, Zamzuri H, Mazlan SA
    Sensors (Basel), 2016 Aug 17;16(8).
    PMID: 27548165 DOI: 10.3390/s16081304
    In recent years, there has been major interest in the exposure to physical therapy during rehabilitation. Several publications have demonstrated its usefulness in clinical/medical and human machine interface (HMI) applications. An automated system will guide the user to perform the training during rehabilitation independently. Advances in engineering have extended electromyography (EMG) beyond the traditional diagnostic applications to also include applications in diverse areas such as movement analysis. This paper gives an overview of the numerous methods available to recognize motion patterns of EMG signals for both isotonic and isometric contractions. Various signal analysis methods are compared by illustrating their applicability in real-time settings. This paper will be of interest to researchers who would like to select the most appropriate methodology in classifying motion patterns, especially during different types of contractions. For feature extraction, the probability density function (PDF) of EMG signals will be the main interest of this study. Following that, a brief explanation of the different methods for pre-processing, feature extraction and classifying EMG signals will be compared in terms of their performance. The crux of this paper is to review the most recent developments and research studies related to the issues mentioned above.
    Matched MeSH terms: Isometric Contraction/physiology*
  13. Selvanayagam VS, Riek S, DE Rugy A, Carroll TJ
    Med Sci Sports Exerc, 2016 09;48(9):1835-46.
    PMID: 27116648 DOI: 10.1249/MSS.0000000000000956
    PURPOSE: Goal-directed movements tend to resemble the characteristics of previously executed actions. Here we investigated whether a single bout of strength training, which typically involves stereotyped actions requiring strong neural drive, can bias subsequent aiming behavior toward the direction of trained forces.

    METHODS: In experiment 1 (n = 10), we tested the direction of force exerted in an isometric aiming task before and after 40 repetitions of 2-s maximal-force ballistic contractions toward a single directional target. In experiment 2 (n = 12), each participant completed three training conditions in a counterbalanced crossover design. In two conditions, both the aiming task and the training were conducted in the same (neutral) forearm posture. In one of these conditions, the training involved weak forces to determine whether the level of neural drive during training influences the degree of bias. In the third condition, high-force training contractions were performed in a 90° pronated forearm posture, whereas the low-force aiming task was performed in a neutral forearm posture. This dissociated the extrinsic training direction from the pulling direction of the trained muscles during the aiming task.

    RESULTS: In experiment 1, we found that aiming direction was biased toward the training direction across a large area of the work space (approximately ±135°; tested for 16 targets spaced 22.5° apart), whereas in experiment 2, we found systematic bias in aiming toward the training direction defined in extrinsic space, but only immediately after high-force contractions.

    CONCLUSION: Our findings suggest that bias effects of training involving strong neural drive generalize broadly to untrained movement directions and are expressed according to extrinsic rather than muscle-based coordinates.

    Matched MeSH terms: Isometric Contraction
  14. Pearson SJ, Mohammed ASA, Hussain SR
    J Biomech, 2017 08 16;61:45-50.
    PMID: 28736078 DOI: 10.1016/j.jbiomech.2017.06.038
    PURPOSE: Descriptive data on the aspects of site specific in vivo tendon strain with varying knee joint angle are non-existent. The present study determines and compares surface and deep layer strain of the patellar tendon during isometric contractions across a range of knee joint angles.

    METHODS: Male participants (age 22.0±3.4) performed ramped isometric knee extensions at knee joint angles of 90°, 70°, 50° and 30° of flexion. Strain patterns of the anterior and posterior regions of the patellar tendon were determined using real-time B-mode ultrasonography at each knee joint angle. Regional strain measures were compared using an automated pixel tracking method.

    RESULTS: Strain was seen to be greatest for both the anterior and posterior regions with the knee at 90° (7.76±0.89% and 5.06±0.76%). Anterior strain was seen to be significantly greater (p<0.05) than posterior strain for all knee angles apart from 30°, 90°=(7.76vs. 5.06%), 70°=(4.77vs. 3.75%), and 50°=(3.74vs. 2.90%). The relative strain (ratio of anterior to posterior), was greatest with the knee joint angle at 90°, and decreased as the knee joint angle reduced.

    CONCLUSIONS: The results from this study indicate that not only are there greater absolute tendon strains with the knee in greater flexion, but that the knee joint angle affects the regional strain differentially, resulting in greater shear between the tendon layers with force application when the knee is in greater degrees of flexion. These results have important implications for rehabilitation and training.

    Matched MeSH terms: Isometric Contraction
  15. Ali A, Sundaraj K, Badlishah Ahmad R, Ahamed NU, Islam A, Sundaraj S
    J Hum Kinet, 2015 Jun 27;46:69-76.
    PMID: 26240650 DOI: 10.1515/hukin-2015-0035
    The objective of the present study was to investigate the time to fatigue and compare the fatiguing condition among the three heads of the triceps brachii muscle using surface electromyography during an isometric contraction of a controlled forceful hand grip task with full elbow extension. Eighteen healthy subjects concurrently performed a single 90 s isometric contraction of a controlled forceful hand grip task and full elbow extension. Surface electromyographic signals from the lateral, long and medial heads of the triceps brachii muscle were recorded during the task for each subject. The changes in muscle activity among the three heads of triceps brachii were measured by the root mean square values for every 5 s period throughout the total contraction period. The root mean square values were then analysed to determine the fatiguing condition for the heads of triceps brachii muscle. Muscle fatigue in the long, lateral, and medial heads of the triceps brachii started at 40 s, 50 s, and 65 s during the prolonged contraction, respectively. The highest fatiguing rate was observed in the long head (slope = -2.863), followed by the medial head (slope = -2.412) and the lateral head (slope = -1.877) of the triceps brachii muscle. The results of the present study concurs with previous findings that the three heads of the triceps brachii muscle do not work as a single unit, and the fiber type/composition is different among the three heads.
    Matched MeSH terms: Isometric Contraction
  16. Kumar A/L S Katheraveloo K, Suryani Safri L, Guo Hou L, Hafiz Maliki A, Md Idris MA, Harunarashid H
    J Vasc Access, 2020 May;21(3):372-378.
    PMID: 31581898 DOI: 10.1177/1129729819879314
    BACKGROUND: Proper vascular access is essential for the long-term survival of chronic haemodialysis patients. The preferred vascular access in terms of long-term function is the native arteriovenous fistula. The success of native arteriovenous fistula depends mainly on a sufficient vein diameter. Thus, any intervention that could increase vein diameter before arteriovenous fistula creation could improve its patency. We conduct a study to investigate the effect of local physical training, namely handgrip exercise, on the distal forearm cephalic vein diameter in patients with chronic renal disease.

    MATERIAL AND METHODS: A total of 34 chronic renal disease patients (stage 3 and 4) were recruited in a randomized controlled trial. Handgrip exercise was performed for 8 weeks in the intervention group. Handgrip-strength measurement and distal forearm cephalic vein diameter of a non-dominant hand with and without tourniquet was recorded (measurement is taken 1 cm proximal to the radial styloid).

    RESULTS: After 8 weeks, the mean cephalic vein diameter in the intervention group increased from 1.77 and 1.97 mm to 2.15 and 2.43 mm, without and with a tourniquet, respectively (p < 0.05). There is also a significant change in the mean diameter of distal forearm cephalic vein (p < 0.05) in the intervention group when measured in both the absence (mean change 0.39 ± 0.06 mm vs 0.01 ± 0.02 mm) and the presence of tourniquet (mean change 0.47 ± 0.07 mm vs 0.01 ± 0.01 mm).

    CONCLUSION: These findings suggest that non-invasive handgrip exercise can increase in the diameter of the distal forearm cephalic vein, thereby increasing the rate of successful arteriovenous fistula creation.

    Matched MeSH terms: Isometric Contraction*
  17. Islam MA, Sundaraj K, Ahmad RB, Sundaraj S, Ahamed NU, Ali MA
    PLoS One, 2014;9(8):e104280.
    PMID: 25090008 DOI: 10.1371/journal.pone.0104280
    In mechanomyography (MMG), crosstalk refers to the contamination of the signal from the muscle of interest by the signal from another muscle or muscle group that is in close proximity.
    Matched MeSH terms: Isometric Contraction
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