The relationships between skinfold, fatigue and the traditional and log-transformed electromyographic and mechanomyographic signal in the vastus lateralis and recuts femoris

INTRODUCTION: The purpose of the present study was to examine possible correlations between skinfold thicknesses and the a terms from the EMGRMS- and MMGRMS-force relationships for the vastus lateralis (VL) and rectus femoris (RF) and EMG M-Wave (EMG M-wave) and MMG gross lateral movement (MMG GLM) of the VL and RF from a non-voluntary single evoked potential. In addition, correlations were calculated between the b terms form the EMGRMS- and MMGRMS-force relationships and the fatigue index from the Thorstensson protocol. METHODS: Forty healthy subjects (age = 21 ± 2 yrs., weight = 73.5 ± 13.2 kg, height = 1.7 ± 0.09 m) performed a 6-second isometric ramp contraction followed by transcutaneous electrical stimuli at rest and a 50-repetition fatigue protocol. EMG and MMG sensors were placed on the VL and RF on the center of the muscle belly with skinfold thickness assessed at the site of the electrodes. Transcutaneous stimuli were delivered to the femoral nerve via a bipolar surface electrode that was placed over the inguinal space to assess EMG M-wave and MMG GLM. Simple linear regression models were fit to the natural log-transformed EMGRMS and MMGRMS-force relationships. The b term and a term were calculated for each relationship. The fatigue index was calculated from the equation: ([Initial Peak Force - Final Peak Force]/Initial Peak Force) x 100. Pearson's product correlation coefficients were calculated comparing VL and RF skinfold thicknesses with the a terms from the EMGRMS-and MMGRMS-force relationships, EMG M-wave, and MMG GLM. In addition correlations were calculated comparing the b terms from the EMGRMS- and MMGRMS-force relationships terms for the VL and RF with the fatigue index. RESULTS: There were no significant correlations found between the a terms and the skinfold thicknesses for the RF (p = 0.614, r = -0.082) and VL (p = 0.507, r = 0.108) from the EMGRMS-force relationships and the RF (p = 0.508, r = 0.108) and VL (p = 0.546, r = 0.098) from the MMGRMS-force relationships. In contrast, there were significant correlations between skinfold thicknesses and the EMG M-waves for the RF (p = 0.002, r = -0.521) and VL (p = 0.005, r = -0.479) and for the MMG GLM for the RF (p = 0.031, r = -0.376) and VL (p = 0.004, r = -0.484). Finally, significant correlations were found between the b terms from the MMGRMS-force relationships for the VL (p = 0.007, r = 0.417) and RF (p = 0.014, r = 0.386) with the fatigue index. In addition, the b terms from the EMGRMS-force relationships for the RF (p = 0.017, r = 0.375) were correlated with the fatigue index, however, the b terms for the VL (p = 0.733, r = 0.056) were not correlated with the fatigue index. DISCUSSION: The correlations between the b terms and fatigue index suggested that the log-transformed MMGRMS-force relationship model may reflect muscle fiber type composition. Regarding the EMGRMS-force relationships, it is unclear why the b terms from the RF and not the VL were correlated with the fatigue index. The a terms from the log-transformed EMGRMS- and MMGRMS-force relationships were not correlated with skinfold thicknesses, whereas, the EMG M-wave and MMG GLM produced from non-voluntary evoked twitches were correlated with skinfold thicknesses

Noninvasive assessment of inspiratory muscle neuromechanical coupling during inspiratory threshold loading

Diaphragm neuromechanical coupling (NMC), which reflects the efficiency of conversion of neural activation to transdiaphragmatic pressure (Pdi), is increasingly recognized to be a useful clinical index of diaphragm function and respiratory mechanics in neuromuscular weakness and cardiorespiratory disease. However, the current gold standard assessment of diaphragm NMC requires invasive measurements of Pdi and crural diaphragm electromyography (oesEMGdi), which complicates the measurement of diaphragm NMC in clinical practice. This is the first study to compare invasive measurements of diaphragm NMC (iNMC) using the relationship between Pdi and oesEMGdi, with noninvasive assessment of NMC (nNMC) using surface mechanomyography (sMMGlic) and electromyography (sEMGlic) of lower chest wall inspiratory muscles. Both invasive and noninvasive measurements were recorded in twelve healthy adult subjects during an inspiratory threshold loading protocol. A linear relationship between noninvasive sMMGlic and sEMGlic measurements was found, resulting in little change in nNMC with increasing inspiratory load. By contrast, a curvilinear relationship between invasive Pdi and oesEMGdi measurements was observed, such that there was a progressive increase in iNMC with increasing inspiratory threshold load. Progressive recruitment of lower ribcage muscles, serving to enhance the mechanical advantage of the diaphragm, may explain the more linear relationship between sMMGlic and sEMGlic (both representing lower intercostal plus costal diaphragm activity) than between Pdi and crural oesEMGdi. Noninvasive indices of NMC derived from sEMGlic and sMMGlic may prove to be useful indices of lower chest wall inspiratory muscle NMC, particularly in settings that do not have access to invasive measures of diaphragm function.Peer ReviewedPostprint (published version

Mechanomyographic Parameter Extraction Methods: An Appraisal for Clinical Applications

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

Advances and perspectives of mechanomyography

INTRODUCTION: The evaluation of muscular tissue condition can be accomplished with mechanomyography (MMG), a technique that registers intramuscular mechanical waves produced during a fiber's contraction and stretching that are sensed or interfaced on the skin surface. OBJECTIVE: Considering the scope of MMG measurements and recent advances involving the technique, the goal of this paper is to discuss mechanomyography updates and discuss its applications and potential future applications. METHODS: Forty-three MMG studies were published between the years of 1987 and 2013. RESULTS: MMG sensors are developed with different technologies such as condenser microphones, accelerometers, laser-based instruments, etc. Experimental protocols that are described in scientific publications typically investigated the condition of the vastus lateralis muscle and used sensors built with accelerometers, third and fourth order Butterworth filters, 5-100Hz frequency bandpass, signal analysis using Root Mean Square (RMS) (temporal), Median Frequency (MDF) and Mean Power Frequency (MPF) (spectral) features, with epochs of 1 s. CONCLUSION: Mechanomyographic responses obtained in isometric contractions differ from those observed during dynamic contractions in both passive and functional electrical stimulation evoked movements. In the near future, MMG features applied to biofeedback closed-loop systems will help people with disabilities, such as spinal cord injury or limb amputation because they may improve both neural and myoelectric prosthetic control. Muscular tissue assessment is a new application area enabled by MMG; it can be useful in evaluating the muscular tonus in anesthetic blockade or in pathologies such as myotonic dystrophy, chronic obstructive pulmonary disease, and disorders including dysphagia, myalgia and spastic hypertonia. New research becomes necessary to improve the efficiency of MMG systems and increase their application in rehabilitation, clinical and other health areas304384401CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFINANCIADORA DE ESTUDOS E PROJETOS - FINEPsem informaçã

Quantification of patellar tendon reflex using portable mechanomyography and electromyography devices

Deep tendon reflexes are one of the main components of the clinical nervous system examinations. These assessments are inexpensive and quick. However, evaluation can be subjective and qualitative. This study aimed to objectively evaluate hyperreflexia of the patellar tendon reflex using portable mechanomyography (MMG) and electromyography (EMG) devices. This study included 10 preoperative patients (20 legs) who had a pathology that could cause bilateral patellar tendon hyperreflexia and 12 healthy volunteers (24 legs) with no prior history of neurological disorders. We attached MMG/EMG sensors onto the quadriceps and tapped the patellar tendon with maximal and constant force. Our results showed a significantly high amplitude of the root mean square (RMS) and low frequency of the mean power frequency (MPF) in the rectus femoris, vastus medialis, and vastus lateralis muscles in both EMG and MMG with both maximal and constant force. Especially in the patients with cervical and thoracic myelopathy, the receiver operating characteristic (ROC) curve for diagnosing hyperreflexia of the patellar tendon showed a moderate to very high area under the curve for all EMG-RMS, EMG-MPF, MMG-RMS, and MMG-MPF values. The use of EMG and MMG for objectively quantifying the patellar tendon reflex is simple and desirable for future clinical applications and could help diagnose neurological disorders

A Review of Non-Invasive Techniques to Detect and Predict Localised Muscle Fatigue

Muscle fatigue is an established area of research and various types of muscle fatigue have been investigated in order to fully understand the condition. This paper gives an overview of the various non-invasive techniques available for use in automated fatigue detection, such as mechanomyography, electromyography, near-infrared spectroscopy and ultrasound for both isometric and non-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 wish to select the most appropriate methodology for research on muscle fatigue detection or prediction, or for the development of devices that can be used in, e.g., sports scenarios to improve performance or prevent injury. To date, research on localised muscle fatigue focuses mainly on the clinical side. There is very little research carried out on the implementation of detecting/predicting fatigue using an autonomous system, although recent research on automating the process of localised muscle fatigue detection/prediction shows promising results

Mechanomyographic amplitude and frequency responses during dynamic muscle actions: a comprehensive review

The purpose of this review is to examine the literature that has investigated mechanomyographic (MMG) amplitude and frequency responses during dynamic muscle actions. To date, the majority of MMG research has focused on isometric muscle actions. Recent studies, however, have examined the MMG time and/or frequency domain responses during various types of dynamic activities, including dynamic constant external resistance (DCER) and isokinetic muscle actions, as well as cycle ergometry. Despite the potential influences of factors such as changes in muscle length and the thickness of the tissue between the muscle and the MMG sensor, there is convincing evidence that during dynamic muscle actions, the MMG signal provides valid information regarding muscle function. This argument is supported by consistencies in the MMG literature, such as the close relationship between MMG amplitude and power output and a linear increase in MMG amplitude with concentric torque production. There are still many issues, however, that have yet to be resolved, and the literature base for MMG during both dynamic and isometric muscle actions is far from complete. Thus, it is important to investigate the unique applications of MMG amplitude and frequency responses with different experimental designs/methodologies to continually reassess the uses/limitations of MMG

EXAMINATION OF PHYSIOLOGICAL AND PERCEPTUAL RESPONSES DURING SUSTAINED, ISOMETRIC, FATIGUING, HANDGRIP EXERCISE ANCHORED TO RATINGS OF PERCEIVED EXERTION

The purposes of this study were to: 1) Examine the patterns of force responses relative to critical force (CF) during submaximal, fatiguing, isometric handgrip exercise anchored to different rating of perceived exertion (RPE) levels (RPE=3, 5, and 7); 2) assess the loss of force during the task and the level of performance fatigability after each RPE hold; 3) examine the time course of changes and patterns of neuromuscular [electromyography (EMG) amplitude (AMP), mean power frequency (MPF), mechanomyography (MMG) AMP and MPF, and neuromuscular efficiency (NME) (i.e. force/EMG AMP)] and muscle oxygen saturation (% SmO2) responses during each RPE hold; 4) examine which theory (i.e. corollary discharge, afferent feedback, sensory tolerance limit) best explains the regulation of exercise during each RPE hold. Twelve, healthy men between 18 and 35 years performed submaximal, continuous, isometric contractions to task failure at one of four randomly determined percentages of maximal voluntary isometric contraction (MVIC) (30, 40, 50, and 60%) on separate days. The amount of work performed (Wlim) was obtained by multiplying the force by the corresponding time to task failure (Tlim). The four Wlim values were plotted as a linear function of the Tlim values, and the CF was defined as the slope coefficient of Wlim versus Tlim relationship. Subjects performed constant RPE handgrip holds at one of the three randomly ordered RPE levels (RPE= 3, 5, and 7). EMG and MMG, AMP and MPF were calculated in standardized segments of 5% Tlim (0-100% Tlim) during each hold and normalized to the respective values at the pre-MVIC. SmO2 response was recorded in standardized segments of 5% Tlim (5-100% Tlim). For the Tlim and performance fatigability, 2(Time: pre- vs post-hold) x 3(RPE: 3, 5, and 7) repeated measure ANOVAs and post-hoc t-tests with a Bonferroni corrected alpha level (plim) repeated measures ANOVAs, with follow up one-way repeated measures ANOVAs and post-hoc t-tests with Bonferroni for comparisons across time (p2 responses, a 3(RPE: 3, 5, and 7) x 20(time: 5-100% MVIC) repeated measures ANOVA, with a follow up one-way ANOVA and post-hoc t-tests with Bonferroni for comparisons across time (plim between RPE 3, 5, and 7 (p=0.569-0.744). There were decreases in force, relative to the initial value (0% Tlim), from 20% to 100% Tlim for RPE 3, from 45% to 100% Tlim for RPE 5, and from 15% to 100% Tlim for RPE 7. Based on the force profiles for each RPE, the patterns of responses were examined according to three phases, phase 1 (initial force to 15% Tlim), phase 2, (20-85% Tlim), and phase 3 (90-100% Tlim). For the performance fatigability, there were no difference in pre-MVIC (p=0.494-0.894) among RPE 3, 5, and 7, but the post-MVIC value of RPE 3 was greater than RPE 5 (p=0.008), but not RPE 7 (p=0.024), and there was no difference in RPE 5 and 7 (p=0.924). For EMG AMP, there were decreases, relative to 0% Tlim, at 20% and 25%, and from 35% to 100% Tlim at RPE 3, at 30%, 55%, 60%, and 100% Tlim at RPE 5, and at 30% and from 40% to 100% Tlim at RPE 7. For EMG MPF, there were decreases, relative to 0% Tlim, at 15%, 25%, 30%, and from 45% to 95% Tlim, collapsed across RPE. For MMG AMP, there were no significant changes, relative to 0% Tlim, at any time points (p=0.005-0.036), collapsed across RPE, and RPE 7 was greater than RPE 3 (p=0.013) and RPE 5 (p=0.001), collapsed across time. For MMG MPF, there were no significant changes, relative to 0% Tlim, at any time points (p=0.027-0.920). For NME, there were no differences, relative to 0% Tlim, at any time points (p=0.004-0.780) for RPE 3 but decreases from 50% to 65% and from 80% to 100% for RPE 5, and a decrease at the last time point (100% Tlim) for RPE 7. For SmO2, there was no significant differences, relative to the initial value (5% Tlim), at any time point for RPE 3,5, and 7 (p=0.017-0.774). Overall, during phase 1 (0-15% Tlim), the integrated process of anticipatory (i.e., feedforward) regulation and group III afferent neurons (i.e., inhibitory feedback) was likely primarily responsible for the decrease in force. However, afferent feedback primarily from group IV neurons may also have led to force reductions in the later stages of phase 1 and carried over into phase 2 (20-85% Tlim). During phase 2 and 3 (90-100% Tlim), a combination of afferent feedback and the feedforward pathway via corollary discharges likely contributed to the continuous, voluntary reduction in force to maintain the predetermined RPEs. In phase 3, the sensory tolerance limit (i.e., sum of afferent feedback and feedforward signals) may explain the force reduction to task failure at a similar time across each RPE. This study suggested that force alterations, the accompanying metabolic and/or neuromuscular responses, and performance fatigability were affected by different mechanisms depending on phases (1 vs. 2 and 3) and/or RPE (3 vs. 5 vs. 7), which may provide insights when prescribing continuous or repetitive handgrip tasks in occupational or industrial settings

AN EXAMINATION OF THE EFFECTS OF BILATERAL AND UNILATERAL VERY SHORT-TERM DCER TRAINING ON STRENGTH AND NEUROMUSCULAR RESPONSES WITHIN THE LOWER LIMB BILATERAL DEFICIT

The very short-term resistance training (VST) model, utilizing only 2-3 training sessions, has been used to examine early phase skeletal muscle, neural, and performance adaptations. The VST model has previously been used to examine these early phase adaptations in bilateral and unilateral, isometric, isokinetic, and dynamic muscle actions in the limbs of the upper- and lower-body. The bilateral deficit (BLD) is a phenomenon in which the sum of the forces produced unilaterally is greater than the force produced bilaterally during maximal contraction of the limbs. The appearance of a bilateral deficit has been be related to various factors; including training status and mode of training (bilateral versus reciprocal muscle actions). No previous study, however, has examined the effects of VST on the BLD. The VST model has potential implications for examining acute changes in strength and neuromuscular responses of the trained muscles. These adaptations, however, may be specific to unilateral or bilateral training. Therefore, the purposes of this study were to: 1) examine one repetition maximum (1RM) strength and neuromuscular responses (EMG AMP, EMG MPF, MMG AMP, MMG MPF) during the measurement of bilateral and unilateral leg extension exercise before and after dynamic constant external resistance (DCER) VST; 2) examine the magnitude of the BLD; 3) examine the effect of bilateral versus unilateral training on the BLD; and 4) use the neuromuscular responses measured bilaterally and unilaterally to infer about the motor unit activation strategies that may underlie the BLD and changes in 1RM strength. Twenty-four (14 males, 10 females) subjects (mean ± SD age: 23.0 ± 3.2 yr; height: 174.7 ± 8.5 cm; body mass: 75.4 ± 14.1 kg) with no resistance training experience within the last three months were randomly assigned to either the bilateral (BL) training group or the unilateral (UL) training group. The subjects completed a total of seven visits, consisting of a familiarization, pre-test visit, three training visits, and one post-test visit. The pre-test visit was used to record the subject’s electromyographic (EMG) and mechanomyographic (MMG) responses from the right and left vastus lateralis (VL) during bilateral and unilateral seated maximum isometric voluntary contractions (MVIC) and 1RM. Visits four through six were the training sessions, with each subject preforming 5 sets of 6 repetitions utilizing 65% of the 1RM for resistance where the BL group trained both limbs (right and left) at the same time and the UL group trained both limbs separately. Visit seven was the post-test and the same testing procedures as the pre-test visit were followed. Statistical analyses consisted of four-way and three-way mixed model ANOVAs, with follow up three-, two- and one-way repeated measures and/or mixed model ANOVAs, Bonferroni corrected paired, and independent samples t-tests when appropriate. An alpha level of P ≤ 0.05 was considered statistically significant for all ANOVAs. The BL group demonstrated a significant increase (p = 0.006; 6.8%) in BL1RM pre- to post-test, but no change in unilateral summed (US1RM = right + left limb; p = 0.726) 1RM strength. The UL group demonstrated an 8.7% increase in BL strength collapsed across testing mode (BL1RM and US1RM) (p = 0.0001) and UL strength (p = 0.0001) collapsed across limb (UL left + UL right/2) from pre- to post-test. The BL group had a significant (p = 0.001) increase in the BI (indicating a decrease in the BLD) from pre- to post-test, but there was no significant change for the UL group. The BL group demonstrated a significant (p = 0.029) decrease in the EMG mean power frequency (MPF) measurement pre- to post-test, however the UL group showed no change. The unilateral movement, collapsed across limbs (unilateral left and unilateral right) also showed a significant (p = 0.022) decrease in the MMG MPF measurement pre- to post-test, whereas the BL movement showed no change. These findings indicated that BL and UL DCER training increased strength after 3 training sessions. The bilateral DCER training resulted in bilateral, but not unilateral strength increases and unilateral DCER training resulting in both bilateral and unilateral strength increases. However, bilateral training was the only mode of training that significantly decreased the BLD