Mean Electromyographic Amplitude Research Articles

Normalization of the hip abductors rate of activation during a voluntary step task in older adults: Reliability and differences among approaches

BackgroundVoluntary stepping tasks are used to measure the ability of an individual to step and has been associated with fall risk in older adults. Although electromyography (EMG) amplitude is measured during stepping tasks, there is no consensus about the reference EMG value that should be used to normalize the signal. The purpose of the present study was to 1) investigate the impact of using different EMG parameters as a reference to normalize the rate of activation (RoA) of the hip abductor muscles across lateral voluntary step trials and the differences between trials, and 2) to investigate the reliability among trials of the reference EMG values. MethodsNineteen older adults (>65 years of age) performed ten lateral choice reaction stepping test (CRST), while the gluteus medius and tensor fascia latae EMG were recorded. Three reference EMG values were calculated and used to normalize RoA during the stepping task. A repeated-measures ANOVA was used (normalized RoA[3] x trial[3]) to compare normalized EMG across trials, and an intraclass correlation coefficient and coefficient of variation were used for the inter-trial reliability of the reference EMG values. ResultsThe present study showed that gluteus medius and tensor fascia latae RoA normalized values from the stance and stepping leg (right or left side) measured during CRST are different according to the reference EMG value(P<0.001), with no differences across trials. Overall, the EMG procedures showed high inter-trial reliability, with a few exceptions. SignificanceTherefore, after careful examination of our results, the peak and mean EMG amplitudes showed consistently higher intraclass correlation coefficients; however, the former may provide a more intuitive reference value.

Control of motor output during steady submaximal contractions is modulated by contraction history.

The purpose of the study was to investigate the influence of contraction history on force steadiness and the associated EMG activity during submaximal isometric contractions performed with the dorsiflexor muscles. The key feature of the protocol was a triangular ramp contraction performed in the middle of a steady contraction at a lower target force. The target force during the ramp contraction was 20% MVC greater than that during the steady contraction. Thirty-seven healthy individuals (21 men and 16 women) performed the submaximal tasks with the ankle dorsiflexors. Electromyography (EMG) signals were recorded from tibialis anterior with a pair of surface electrodes. The coefficient of variation for force was significantly greater during the second steady contraction compared with the first one at each of the seven target forces (p<0.015; d=0.38-0.92). Although the average applied force during the steady contractions before and after the triangular contraction was the same (p=0.563), the mean EMG amplitude for the steady contractions performed after the triangular contraction was significantly greater at each of the seven target forces (p<0.0001; d=0.44-0.68). Also, there were significant differences in mean EMG frequency between the steady contractions performed before and after the triangular contraction (p<0.01; d=0.13-0.82), except at 10 and 20% MVC force. The greater force fluctuations during a steady submaximal contraction after an intervening triangular contraction indicate a change in the discharge characteristics of the involved motor units.

Forelimb muscle activation patterns in American alligators: Insights into the evolution of limb posture and powered flight in archosaurs.

The evolution of archosaurs provides an important context for understanding the mechanisms behind major functional transformations in vertebrates, such as shifts from sprawling to erect limb posture and the acquisition of powered flight. While comparative anatomy and ichnology of extinct archosaurs have offered insights into musculoskeletal and gait changes associated with locomotor transitions, reconstructing the evolution of motor control requires data from extant species. However, the scarcity of electromyography (EMG) data from the forelimb, especially of crocodylians, has hindered understanding of neuromuscular evolution in archosaurs. Here, we present EMG data for nine forelimb muscles from American alligators during terrestrial locomotion. Our aim was to investigate the modulation of motor control across different limb postures and examine variations in motor control across phylogeny and locomotor modes. Among the nine muscles examined, m. pectoralis, the largest forelimb muscle and primary shoulder adductor, exhibited significantly smaller mean EMG amplitudes for steps in which the shoulder was more adducted (i.e., upright). This suggests that using a more adducted limb posture helps to reduce forelimb muscle force and work during stance. As larger alligators use a more adducted shoulder and hip posture, the sprawling to erect postural transition that occurred in the Triassic could be either the cause or consequence of the evolution of larger body size in archosaurs. Comparisons of EMG burst phases among tetrapods revealed that a bird and turtle, which have experienced major musculoskeletal transformations, displayed distinctive burst phases in comparison to those from an alligator and lizard. These results support the notion that major shifts in body plan and locomotor modes among sauropsid lineages were associated with significant changes in muscle activation patterns.

Acute Neuromuscular Fatigability and Perceived Exertion in High-Level University Pianists: An Electromyography and Maximum Force Capacity Study.

Musicians are labelled 'fine motor athletes' due to the significant demands of practice and performance. In response, sports medical concepts and expertise have been adapted and mobilized to address musicians' health considerations. However, understanding distinct differences between the sports and performing arts medical contexts is critical. Mismanagement of fatigue and acute fatigability are identified as key risk factors for deleterious symptoms and injuries in musicians. Acute fatigability in athletes and musicians have been assumed to occur similarly, although this has yet to be empirically demonstrated. This study aimed to evaluate acute muscular performance fatigability during piano performance of varied intensities. Fourteen university pianists attended a single experimental session and performed three pieces of randomly ordered repertoire for 10 minutes each. Repertoire were self-selected to be physically easy (rating of perceived exertion [RPE] 9/20), somewhat hard (RPE 13/20), or hard (RPE 17/20). At baseline, after each repertoire performance, and following a concluding 10-minute silent sitting period, participants completed maximum voluntary contraction (MVC) grip and shoulder strength tests. Surface electromyographic (EMG) data were obtained from bilateral upper trapezius and forearm flexor and extensor muscles. Data were analyzed using uni- and multivariate repeated measures analyses of variance (ANOVAs). No evidence of muscular performance fatigability was found in study pianists at any intensity. Mean EMG amplitude and average median EMG frequency did not significantly vary during any repertoire performances or MVC tests (F≤1.72; p>0.09). Additionally, no changes in force or EMG parameters were found during any MVC tests (F≤1.19; p>0.31). The absence of muscular performance fatigability during even the most intense piano performances suggests substantially differing mechanisms of fatigability and perceived exertion in pianists versus those commonly seen in sport athletes. Further research is needed to understand the mechanisms of acute fatigability in musicians and develop musician-specific management strategies.

Effects of Relative Inertial Load on Quadriceps Electromyography during Maximal Effort Flywheel-based Iso-Inertial Training (FIT) Squats

The effects of inertial load on quadriceps electromyography (EMG) during flywheel-based iso-inertial training (FIT) squats is unclear. Healthy, resistance-trained males (n=8) and females (n=8) completed five sets of five maximal-effort squats with varying inertial loads in a randomized order. Sagittal plane knee joint angles and surface EMG activity of the vastus lateralis (VL) were measured. Average knee angular velocity, but not peak knee flexion or total excursion, decreased during both the concentric and eccentric phases with increasing inertial load (p&lt;0.001) in both sexes. Integrated EMG (iEMG) activity increased with increasing inertial load for all muscles (p&lt;0.001). VL iEMG and peak amplitude were significantly greater in females. However, peak EMG amplitude was not significantly different among inertial loads for either sex. Mean EMG amplitude during the concentric phase and eccentric phases of the VL tended to be greater in females. Increasing relative inertial load increases quadriceps iEMG activity due to greater exercise duration, but has minimal effects on EMG amplitude.

The influence of idiopathic chronic neck pain on upper trapezius and sternocleidomastoid muscle activity and elasticity during functional reaching: A cross-sectional study

It remains unclear whether idiopathic chronic neck pain is associated with changes in muscle stiffness alongside alterations in neuromuscular control. Therefore, the purpose of this study was to determine the influence of idiopathic chronic neck pain on the muscle stiffness and muscle activity of the upper trapezius and sternocleidomastoid muscles during the maintenance of unilateral and bilateral functional reaching tasks. Surface electromyography (EMG) and ultrasound shear wave elastography were collected from the sternocleidomastoid and upper trapezius muscles in 18 individuals with idiopathic chronic neck pain and 18 matched healthy controls. Participants completed three functional reaching tasks; 1) unilateral forward reach, 2) bilateral forward reach, and 3) unilateral upward reach, and held at the top of each reaching movement for data to be collected bilaterally. A univariate ANOVA was utilized for each outcome measure (mean EMG amplitude and shear wave velocity) and each reaching task. Individuals with idiopathic chronic neck pain exhibited significantly lower upper trapezius activation during bilateral reaches without corresponding changes to stiffness during similar trials. Similarly, this cohort exhibited decreased sternocleidomastoid stiffness during forward reaching, without corresponding activation changes. Lastly, women demonstrated consistently higher sternocleidomastoid activation and stiffness when compared to men. These findings indicate individuals with idiopathic chronic neck pain may adapt their movement strategies, possibly for pain avoidance. The demonstrated changes in muscle stiffness independent of changes in muscle activity highlight the importance of evaluating both muscle stiffness and activation in individuals with idiopathic chronic neck pain prior to designing rehabilitation programs.

Quadriceps electromyography during flywheel-based inertial training (FIT) and dynamic constant external resistance (DCER) squats at similar tempo

ABSTRACT Flywheel-based iso-inertial training (FIT) has been purported to provide enhanced adaptations to muscle overload compared to dynamic constant external resistance (DCER), but previous studies have not controlled for exercise intensity. We compared quadriceps electromyography (EMG) amplitude between FIT- and DCER-squats with similar tempo. Eleven (5 M and 6F) resistance-trained participants completed sets of five maximal velocity FIT (0.025 kg∙m2) and DCER (55 ± 15 %1RM) squats. Sagittal plane knee joint angles and surface EMG activity of the vastus lateralis (VL), vastus medialis (VM) and rectus femoris (RF) were measured. Repetition time and peak knee angles were similar between FIT and DCER squats. Mean knee angular velocity during the concentric (122.2 ± 23.6 vs. 108.9 ± 22.9, p = 0.022, Cohen’s D: 0.820), but not eccentric, phase was significantly greater during FIT. Peak VM (210.4 ± 49.3 vs. 177.5 ± 56.3 %MVIC, p = 0.001; Cohen’s D: 1.416), but not VL or RF, EMG amplitude was significantly greater in FIT compared to DCER. Mean EMG amplitude was significantly (p < 0.001) greater during the concentric than the eccentric phase for the VL and VM but not RF. Mean EMG amplitude was not significantly different between modes during either the concentric or eccentric phase. Quadriceps EMG amplitude is largely similar between FIT and DCER squats when matched for movement velocity.

Design and Evaluation of a Custom-Made Electromyographic Biofeedback System for Facial Rehabilitation.

BackgroundIn the rehabilitation of postoperative facial palsy, physical therapy is of paramount importance. However, in the early rehabilitation phase, voluntary movements are often limited, and thus, the motivation of patients is impacted. In these situations, biofeedback of facial electromyographic (EMG) signals enables the visual representation of the rehabilitation progress, even without apparent facial movements. In the present study, we designed and evaluated a custom-made EMG biofeedback system enabling cost-effective facial rehabilitation.MethodsThis prospective study describes a custom-made EMG system, consisting of a microcontroller board and muscle sensors, which was used to record the EMG of frontal and zygomatic facial muscles during frowning and smiling. First, the mean EMG amplitudes and movement onset detection rates (ACC) achieved with the custom-made EMG system were compared with a commercial EMG device in 12 healthy subjects. Subsequently, the custom-made device was applied to 12 patients with and without postoperative facial paresis after neurosurgical intervention. Here, the ratio [laterality index (LI)] between the mean EMG amplitude of the healthy and affected side was calculated and related to the facial function as measured by the House and Brackmann scale (H&B) ranging from 1 (normal) to 6 (total paralysis).ResultsIn healthy subjects, a good correlation was measured between the mean EMG amplitudes of the custom-made and commercial EMG device for both frontal (r = 0.84, p = 0.001) and zygomatic muscles (r = 0.8, p = 0.002). In patients, the LI of the frontal and zygomatic muscles correlated significantly with the H&B (r = −0.83, p = 0.001 and r = −0.65, p = 0.023). The ACC of the custom-made EMG system varied between 65 and 79% depending on the recorded muscle and cohort.ConclusionThe present study demonstrates a good application potential of our custom-made EMG biofeedback device to detect facial EMG activity in healthy subjects as well as patients with facial palsies. There is a correlation between the electrophysiological measurements and the clinical outcome. Such a device might enable cost-efficient home-based facial EMG biofeedback. However, movement detection accuracy should be improved in future studies to reach ranges of commercial devices.

Aerobic Capacity Determines Habitual Walking Acceleration, Not Electromyography-Indicated Relative Effort

Objective: Habitual walking is important for health and can be measured with accelerometry, but accelerometry does not measure physiological effort relative to capacity. We compared accelerometer-measured absolute intensity and electromyography (EMG)-measured relative muscle activity between people with low versus excellent aerobic fitness levels during their habitual walking. Methods: Forty volunteers (19 women; age 49.3 ± 17.1 years, body mass index 24.0 ± 2.6 kg/m2; peak oxygen uptake 40.3 ± 12.5 ml/kg/min) wore EMG-shorts and a hip-worn accelerometer simultaneously for 11.6 ± 2.2 hr on 1.7 ± 1.1 days. Continuous gait bouts of at least 5-min duration were identified based on acceleration mean amplitude deviation (MAD, in milli gravitational acceleration, mg) and mean EMG amplitude, with EMG normalized to maximal isometric knee extension and flexion (EMG, in percentage of maximal voluntary contraction EMG). Peak oxygen uptake was measured on a treadmill and maximal strength in isometric leg press (leg press max). MAD and EMG were compared between age- and sex-specific fitness groups (low-average, good, and excellent) and in linear models. Results: During habitual walking bouts (4.1 ± 4.1 bouts/day, 0.9 ± 1.0 min/bout), the low-average fit participants had an approximately 28% lower MAD (245 ± 64.3 mg) compared with both good fit and excellent fit participants (313 ± 68.1 mg, p &lt; .05), but EMG was the same (13.1% ± 8.42% maximal voluntary contraction EMG, p = .10). Absolute, relative to body mass, and relative to skeletal muscle mass peak oxygen uptake (but not leg press max) was positively associated with MAD independent of age and sex (p &lt; .01), but there were no associations with EMG. Conclusions: People with low-average aerobic capacity habitually walk with a lower accelerometer-measured absolute intensity, but the physiological stimulus for lower-extremity muscles is similar to those with excellent aerobic capacity. This should be considered when measuring and prescribing walking for health.

Minute oscillation stretching: A novel modality for reducing musculo-tendinous stiffness and maintaining muscle strength.

A novel stretching modality was developed to provide repetitive small length changes to the plantar flexors undergoing passive stretch defined as "minute oscillation stretching" (MOS). This study investigated the effects of MOS on neuromuscular activity during force production, the rate of torque development (RTD), and the elastic properties of the plantar flexors and Achilles tendon. Ten healthy males participated in this study. The neuromuscular activity of the triceps surae and tibialis anterior muscles during maximal voluntary plantar flexion torque [MVT], RTD of plantar flexion, Achilles tendon stiffness, and muscle stiffness were measured before and after two types of interventions for a total of 5 minutes: static stretching (SS) and MOS at 15 Hz and without intervention (control). Achilles tendon stiffness was calculated from the tendon elongation measuring by ultrasonography. Muscle stiffness was determined for the medial gastrocnemius [MG] using shear wave elastography. The MVT, mean electromyographic amplitudes [mEMG] of MG and lateral gastrocnemius [LG], and RTD were significantly decreased following SS (MVT: −7.2 ± 7.9%; mEMG of MG: −8.7 ± 10.2%; mEMG of LG: −12.4 ± 10.5%; RTD: −6.6 ± 6.8%), but not after MOS. Achilles tendon stiffness significantly decreased after SS (−13.4 ± 12.3%) and MOS (−9.7 ± 11.5%), with no significant differences between them. Muscle stiffness significantly decreased in SS and MOS, with relative changes being significantly greater for MOS (−7.9 ± 8.3%) than SS (−2.3 ± 2.9%) interventions. All variables remained unchanged in the controls. In conclusion, MOS changed muscle‐tendon compliance without loss of muscle function.

Efficacy of Transcartilaginous Electrodes for Intraoperative Neural Monitoring During Thyroid Surgery

Objectives.This study was conducted evaluate the efficacy of electromyography (EMG) using transcartilaginous (TC) electrodes through the thyroid cartilage and perichondrium.Methods.We prospectively collected EMG data from intraoperative neuromonitoring (IONM) of 54 nerves at risk in 38 patients during thyroidectomy. We followed standardized IONM procedures in all operations. EMG signals from both endotracheal tube (ET) electrodes and TC needle electrodes were recorded simultaneously. We compared the characteristics of the EMG signals and the efficacy of both methods.Results.Significantly higher mean EMG amplitudes were recorded by TC electrodes than by ET electrodes in all four-step procedures (V1-R1-R2-V2, P<0.001). Loss of signal (LOS) occurred in five patients in ET electrodes, but in only two patients in TC electrodes. Postoperative laryngoscopy revealed recurrent laryngeal nerve palsy in the two patients who showed LOS from both the ET and TC electrodes, and vocal cord movement was intact in the other three patients. Therefore, the positive predictive values of LOS in ET and TC electrodes were 40% and 100%, respectively.Conclusion.EMG recording using TC needle electrodes is feasible and effective, making it a good alternative technique for IONM.

Biomechanical and Metabolic Effectiveness of an Industrial Exoskeleton for Overhead Work.

Overhead work activities can lead to shoulder pain and serious musculoskeletal disorders (WMSD), such as rotator cuff injury and degeneration. Recently developed exoskeletons show promising results in supporting workers in such activities. In this study, a novel exoskeleton was investigated for two different overhead tasks with twelve participants. To investigate the effects of the device, electromyographic (EMG) signals of different shoulder and adjacent muscles as well as kinematic and metabolic parameters were analyzed with and without the exoskeleton. The mean EMG amplitude of all evaluated muscles was significantly reduced when the exoskeleton was used for the overhead tasks. This was accompanied by a reduction in both heart rate and oxygen rate. The kinematic analysis revealed small changes in the joint positions during the tasks. This study demonstrated the biomechanical and metabolic benefits of an exoskeleton designed to support overhead work activities. The results suggest improved physiological conditions and an unloading effect on the shoulder joint and muscles which are promising indicators that the exoskeleton may be a good solution to reduce shoulder WMSD among workers who carry out overhead tasks on a regular basis.

The Effect of Tactical Tasks and Gear on Muscle Activation of SWAT Officers.

Keeler, JM, Pohl, MB, Bergstrom, HC, Thomas, JM, and Abel, MG. The effect of tactical tasks and gear on muscle activation of SWAT officers. J Strength Cond Res 36(1): 238-244, 2022-Special Weapons and Tactics (SWAT) officers perform a variety of tactical operations while wearing tactical gear. Load carriage has been shown to alter muscle activation in the torso and is also associated with lower back pain, which is a prevalent musculoskeletal injury suffered by SWAT Officers. The purpose of this study was to quantify the effect of tactical gear on muscle activation of torso musculature while performing occupational tasks. Twenty male SWAT Officers (age: 34.7 ± 4.5 years; height: 1.79 ± 0.1 m; body mass: 91.5 ± 17.3 kg) performed 4 tasks (standing, rifle walk, sitting, and shield walk) with and without gear (mass of gear: 13.8 ± 1.9 kg). Mean electromyographic amplitude was evaluated bilaterally for the erector spinae, rectus abdominis, and external oblique muscles during the trials and expressed relative to maximal voluntary isometric contraction (MVIC). Addition of gear significantly increased erector spinae mean muscle activation during the rifle walk task (mean delta: +0.16%). However, no differences in muscle activation were identified for any other muscles between gear conditions (effect size ≤ 0.15). The shield walk produced the highest mean activation for each muscle during different tasks. The dynamic tasks yielded (0.24-4.18% MVIC) greater muscle activation levels than sitting and standing tasks. Despite minimal increases in muscle activation levels with the addition of gear, load carriage is known to increase the risk of acute and chronic injury. Collectively, these findings indicate that SWAT Officers should perform most skills without gear during tactical training to simulate task-specific movement patterns but reduce the risk of musculoskeletal injury.

Impact of Polarized Versus Threshold Training on Fat Metabolism and Neuromuscular Variables in Ultrarunners.

To compare the effects of 2 different intensity distribution training programs (threshold [THR] and polarized [POL]) on fat metabolism and neuromuscular variables. Twenty ultrarunners were allocated to POL (n = 11; age 40.6 [9.7]y, weight 73.5 [10.8]kg, VO2max 55.8 [4.9]mL·kg-1·min-1) or THR group (n = 9; age 36.8 [9.2]y, weight 75.5 [10.4]kg, VO2max 57.1 [5.2]mL·kg-1·min-1) and performed a 12-week training program that consisted of 5 running sessions, 2 strength sessions, and 1 day of full rest per week. Both groups performed similar total training duration and load but with different intensity distribution during running sessions. Resting metabolic rate, fat metabolism, isometric rate of force development (RFD; N·s-1) and maximal voluntary contraction in the knee extensor, and electromyographic amplitude were measured before and after each program. A significant decrease in RFD0-100ms (Δ -13.4%; P ≤ .001; effect size [ES] = 1.00), RFD0-200ms (Δ -11.7%; P ≤ .001; ES = 1.4), and RFDpeak (Δ -18%; P ≤ .001; ES = 1.4) were observed in the POL group. In THR group, a significant increase in mean electromyographic amplitude (Δ 24.4%; P = .02; ES = 1.4) was observed. There were no significant differences between groups in any of the variables. Similar adaptations in fat metabolism and neuromuscular performance can be achieved after 12 weeks of POL or THR intensity distribution. However, THR distribution appears to better maintain strength (RFD) and improve mean electromyographic amplitude. Nevertheless, the combination of both running and maximum strength training could influence on results because of the residual fatigue thus inducing suboptimal adaptations in the POL group.

Modified arytenoid muscle electrode recording method for neuromonitoring during thyroidectomy.

Intraoperative neuromonitoring (IONM) is an important application for protecting recurrent laryngeal nerve (RLN) during thyroid surgery. The method for recording arytenoid muscle electromyography (EMG) signals is reported to be feasible and reliable. However, the parameters of EMG signals are not provided. This study aimed to analyze the clinical characteristics of EMG signal parameters by modifying the insertion direction of needle electrodes. A total of 92 patients who were scheduled to undergo thyroidectomy were recruited. Two paired needle electrodes were inserted in bilateral angle points between rectus cricothyroid muscle and inferior margin of thyroid cartilage (TC) intraoperatively, and then the information from the EMG signals was recorded according to four-step method (V1-R1-R2-V2). Pre-and post-operative laryngo-fiberoscopy was performed to confirm the vocal cord function. A total of 122 RLNs were successfully recorded during thyroidectomy, with the mean EMG amplitude and latency were 1,857±1,718/2,347±2,323 µV and 3.89±1.12/2.26±0.05 ms for V1/R1 signals before resection, and 1,924±1,705/2,450±2,345 µV and 3.87±1.17/2.27±0.08 ms for R2/V2 signals after resection. There were no significant changes before and after resection, and a normal vocal cord movement was observed postoperatively. The amplitude of left nerves was higher than that of the right ones. Furthermore, the latency of the right vagus was shorter than the left ones, but there was no difference in the amplitude and latency between age, sex and pathological types. Modified arytenoid muscle EMG recording method was considered to be safe, feasible and reliable. The latency of right vagus EMG signals were shorter than the left ones, and the amplitude of EMG signals might be related to different sides.

NEUROMUSCULAR ADAPTIONS FOLLOWING A DAILY STRENGTHENING EXERCISE IN INDIVIDUALS WITH ROTATOR CUFF RELATED SHOULDER PAIN: A PILOT CASE-CONTROL STUDY

The goal of therapeutic exercise is to facilitate a neuromuscular response by increasing or decreasing muscular activity in order to reduce pain and improve function. It is not clear what dosage of exercise will create a neuromuscular response. The purpose of this study was to assess the effects following a three-week home program of a daily single exercise, the prone horizontal abduction exercise (PHA), on neuromuscular impairments of motor control as measured by scapular muscle EMG amplitudes, strength, and secondarily outcomes of self-reported pain and function between individuals with and without subacromial pain syndrome. Prospective Case-Control, Pilot Study. Twenty-five individuals participated; eleven with shoulder pain during active and resistive motions (Penn Shoulder Score: 77 ± 11) and 14 matched healthy controls (Penn Shoulder Score: 99 ± 27) (p < 0.001). Participants underwent baseline and follow up testing at three weeks including surface electromyography (EMG) of the serratus anterior, upper, and lower trapezius of the involved (painful group) or matched shoulder (control group) during an elevation task and maximal isometric shoulder strength testing. All participants were instructed in a PHA exercise to be performed daily (3 sets; 10 reps). Subjects logged daily exercise adherence. Neuromuscular adaptations were defined by changes in EMG amplitudes (normalized to MVIC) of serratus anterior, upper trapezius, and lower trapezius and strength. Secondary outcomes of self-reported pain and function were also compared between groups following the three-week intervention. After three weeks of a daily PHA exercise, the painful group demonstrated a greater decrease in baseline-elevated EMG amplitudes in the lower trapezius by 7% (95%CI 2.6-11%) during the concentric phase of the overhead lifting task (p 0.006). EMG amplitudes of the healthy control group did not change at three-week follow-up. Additionally, the change in serratus anterior mean EMG amplitude in the painful group -1.6% (IQR -22.9 to 0.8%) was significantly greater (p 0.033) than the healthy group change score, 2.5% (IQR -2.3 to 5.7%) during the eccentric phase (p 0.034). While the painful group was weaker in abduction and flexion at baseline and at follow up, both groups had a significant increase in all strength measures (p≤0.014). Concurrent with increased strength and normalizing EMG amplitudes, the painful group significantly improved on the Penn Shoulder Score with a mean change 9.8 points (95%CI 7.0, 12.6) (p < 0.001). In this pilot case-control study, a single home exercise performed daily for three weeks demonstrated neuromuscular adaptations with improvements in muscle activity and strength. These were concurrent with modest, yet significant improvements pain and function in individuals with mild rotator cuff related shoulder pain. 3.

Feasibility of Intraoperative Neuromonitoring During Thyroid Surgery Using Transcartilage Surface Recording Electrodes.

Intraoperative neural monitoring (IONM) has gained widespread acceptance as an adjunct to the gold standard of visual identification of the recurrent laryngeal nerve (RLN) during thyroid surgery. Currently, laryngeal electromyography (EMG) recording during IONM is almost always performed using endotracheal tube (ETT) surface electrodes placed adjacent to vocal folds originating from the inner surface of the thyroid cartilage (TC). Therefore, it was hypothesized that surface recording electrodes placed on the outer surface of the TC should enable access to the EMG response of the vocal folds during IONM. The aim of this experimental study was to evaluate the feasibility of the transcartilage approach for laryngeal EMG recording during IONM. A porcine model (12 pigs and 24 RLN sides) with well established applicability in IONM research was used for the experiments. Both ETT electrodes adjacent to vocal folds and adhesive pre-gelled electrodes on the TC were used for EMG recording during IONM. Electrically evoked EMG signals detected by both electrode types were recorded and analyzed. EMG changes during tracheal displacement and RLN traction injury were compared. Both the ETT and TC recording electrodes recorded typical laryngeal EMG waveforms evoked by a 1 mA stimulus current applied on both sides of the RLNs and vagus nerves (VNs). Under RLN stimulation, the mean EMG amplitudes recorded with the ETT and TC electrodes were 973 ± 79 μV and 695 ± 150 μV, respectively. Under VN stimulation, the mean amplitudes were 841 ± 163 μV and 607 ± 162 μV, respectively. When upward displacement of the trachea was experimentally induced, the TC electrodes showed less variation in recorded EMG signals compared to ETT electrodes. When RLN traction stress was experimentally induced, both the ETT and TC electrodes accurately recorded the typical EMG pattern of progressively degrading amplitude and gradual recovery after release of traction. This study confirms the feasibility of using transcartilage surface electrodes for recording laryngeal EMG signals evoked during IONM in an animal model. However, before practical application of this approach in clinical thyroid surgery, further studies are needed to improve electrode designs by optimizing their shapes and sizes, and increasing their adhesive stability and sensitivity.

Transcutaneous Recording During Intraoperative Neuromonitoring in Thyroid Surgery.

Recurrent laryngeal nerve (RLN) palsy remains a major source of morbidity after thyroid surgeries. Intraoperative neural monitoring (IONM) has gained increasing acceptance as an adjunct to standard practice of visual RLN identification. Endotracheal tube (ETT) surface recording electrodes systems are now widely used for IONM; however, a malpositioned ETT can cause false IONM results and requires time-consuming intraoperative verification of the ETT position and readjustment by the anesthesiologist. The aim of this experimental study was to evaluate the feasibility of the transcutaneous approach for recording evoked laryngeal electromyography (EMG) signals during IONM. A porcine model with well-established applicability in IONM research was used. Twelve piglets (24 nerve sides) were enrolled. Electrically evoked EMGs were recorded from surface electrodes on the ETT and from the adhesive pre-gelled surface electrodes on the anterior neck skin. The evoked EMG waveforms were measured and analyzed. The real-time signal stability of the electrodes during tracheal displacement and their accuracy in reflecting adverse EMG changes during RLN stress were evaluated during continuous IONM performed with automatic periodic vagus nerve (VN) stimulation. In all nerves, both the ETT and neck adhesive skin electrodes successfully recorded typical evoked laryngeal EMG waveforms from the RLNs and VNs under stimulation with 1 mA. The transcutaneous electrodes recorded mean EMG amplitudes of 264 μV (±79) under RLN stimulation and 202 μV (±55) under VN stimulation. The electrodes recorded mean EMG latencies of 2.98 ms (±0.20) under RLN stimulation, 4.51 ms (±0.50) under right VN stimulation, and 8.13 ms (±0.94) under left VN stimulation, respectively. When tracheal displacement was experimentally induced, the EMG signals obtained by ETT electrodes varied significantly, but those obtained by transcutaneous electrodes did not. When RLN traction stress was experimentally induced, both ETT and transcutaneous electrodes recorded the same pattern of progressively degrading EMG amplitude with gradual recovery after release of traction. This study confirms the feasibility of transcutaneous recording of evoked laryngeal EMG during IONM. Although this study confirms the stability and accuracy of the transcutaneous approach, it also revealed the need for new electrode designs to improve EMG amplitudes before practical clinical application of this approach.

Comparing two methods to record maximal voluntary contractions and different electrode positions in recordings of forearm extensor muscle activity: Refining risk assessments for work-related wrist disorders.

BACKGROUND:Wrist disorders are common in force demanding industrial repetitive work. Visual assessment of force demands have a low reliability, instead surface electromyography (EMG) may be used as part of a risk assessment for work-related wrist disorders. For normalization of EMG recordings, a power grip (hand grip) is often used as maximal voluntary contraction (MVC) of the forearm extensor muscles. However, the test-retest reproducibility is poor and EMG amplitudes exceeding 100% have occasionally been recorded during work. An alternative MVC is resisted wrist extension, which may be more reliable.OBJECTIVE:To compare hand grip and resisted wrist extension MVCs, in terms of amplitude and reproducibility, and to examine the effect of electrode positioning.METHODS:Twelve subjects participated. EMG from right forearm extensors, from four electrode pairs, was recorded during MVCs, on three separate occasions.RESULTS:The group mean EMG amplitudes for resisted wrist extension were 1.2–1.7 times greater than those for hand grip. Resisted wrist extension showed better reproducibility than hand grip.CONCLUSIONS:The results indicate that the use of resisted wrist extension is a more accurate measurement of maximal effort of wrist extensor contractions than using hand grip and should increase the precision in EMG recordings from forearm extensor muscles, which in turn will increase the quality of risk assessments that are based on these.

The Effect of Split Nerve on Electromyography Signal Pattern in a Rat Model.

Recent developments of prosthetic arm are based on the use of electromyography (EMG) signals. To provide improvements, such as coordinated movement of multiple joints and greater control intuitiveness, higher variability of EMG signals is needed. By splitting a nerve lengthwise, connecting each half to new target muscles, and employing a program to assign each biosignal pattern to a specific movement, we hope to enrich the number of biosignal sites on amputees' stump. We split the gastrocnemius muscle of 12 Sprague-Dawley rats into two muscle heads, searched for the peroneal nerve, divided them lengthwise, and connected one half of the nerve to the tibial nerve innervating both muscle heads (SN_50, n = 8). In another group, we connected the undivided peroneal nerve to the nerve of a single muscle head (non-SN_100, n = 6), while the other muscle head received different innervation (non-SN_0, n = 6). After 10 weeks, we stimulated the peroneal nerve and measured the EMG amplitude. Mean EMG amplitude of the muscle head innervated by one half of the nerve (SN_50; 1.77 [range: 0.71-3.24] mV) and by the undivided nerve (non-SN_100; 3.45 mV [range: 1.13-5.34]) was not significantly different. However, the mean EMG amplitude produced by SN_50 was significantly different from that of the other innervation (i.e., non-SN_0; 0.76 mV [range: 0.41-1.35]), indicating the presence of noise. Split nerve in combination with split-muscle procedure can yield a meaningful EMG signal that might be used to convey the intention of living organism to a machine.