sEMG Amplitude Research Articles

Hip and knee muscles co-activation ratio during hip-focused exercises: a multichannel surface electromyography study

ABSTRACT This study aimed to evaluate the muscle activation ratio of hip and knee during hip-focused exercises. Eleven active university students performed 13 hip-focused exercises frequently used in the treatment of knee disorders. The average sEMG amplitude of tensor fasciae latae (TFL), gluteus medius (GMed), gluteus maximus (GMax), adductor longus (AL), vastus medialis (VM), vastus lateralis (VL), and GMed/AL, GMax/AL, and VL/VM ratios were determined. Repeated-measures analyses of variance were performed to determine if there were differences in muscle activation while performing each of the 13 exercises. Sidelying clam-shell had the highest GMax/AL ratio of all the exercises examined. The hip hike exercise (5.36) had the highest GMed/AL ratio. The VL/VM ratio ranged from 0.77 to 1.16. Based on these results, sidelying clam-shell had the highest GMax/AL ratio. The hip hike exercise had a higher GMed/AL ratio compared to other hip-focused exercises. Additionally, forward lunge, squat, and single-leg squat with resistance band around the knee had the highest activity VL/VM ratio among exercises.

Studies on the hysteresis of trunk muscles-Muscular specificities must be taken into account.

Hysteresis refers to a physical phenomenon in which the response or state of a system depends on both the input variable and its history. Hysteresis phenomena are also observed in biological systems and have been described for the sensorimotor system. The aim of the present study was to determine whether hysteresis phenomena can also be detected in trunk muscles during isometric load-varying situations. To this end, 40 healthy individuals (19 women) were subjected to isometric tests, where the applied load was systematically altered by complete rotations of the entire body in the Earth's gravitational field. The study was conducted with 25%, 50%, and 75% of the upper body weight. Additionally, we varied the starting point (forward tilt and backward tilt) and the direction of rotation. The activity of a total of six trunk muscles was recorded using surface EMG (sEMG). The sEMG amplitudes were compared between the phases of increasing and decreasing load levels for each test situation. Hysteresis behavior was observed in all examined muscles, with the movement half-phase with increasing load showing higher amplitudes than the half-phase with decreasing load. However, this was consistently verifiable only for the multifidus muscle. For the abdominal muscles, the longissimus, and the iliocostalis muscle, the occurrence of hysteresis depended on the starting position: it could only be demonstrated if the starting point was chosen to correspond with the muscles' main force direction. Thus, only the multifidus muscle exhibits a situation-independent hysteresis, whereas all other examined trunk muscles only show this phenomenon if subjected to load already at a loading situation. This indicates a physiologically determined functional weakness for load impacts on primarily unloaded muscles, posing a potential injury risk.

Surface electromyography: A pilot study in canine spinal muscles

In veterinary practice, rehabilitation modalities are often used to help in the recovery of animals affected by InterVertebral Disc Disease (IVDD), a condition frequently observed in chondrodystrophic dog breeds and can lead to Spinal Cord Injury (SCI), resulting in pain, motor impairments and neurological deficits, but there is a lack of objective assessment tools for patient evolution. In this work, an innovative approach using surface ElectroMyoGraphy (sEMG) is proposed to be applied in the field of veterinary medicine rehabilitation. The observed results are thought to be a direct result of nerve compression, leading to unusual patterns of muscle activation; this phenomenon can be attributed to muscle denervation, where the loss of Motor Units (MU) is the primary cause. This is thought to be responsible for the decrease in recorded sEMG amplitude and the increase in frequency observed in the pathological group.•This study involved rigorous animal preparation and signal acquisition protocols, involving multiple exercises and sub-movements, which were subsequently analysed.•RMSA is most used metric to analyse amplitude in sEMG signals, as it results in a more representative measurement of the signal variability than the Mean amplitude or the Standard Deviation.

Right-left sEMG burst synchronization of the lumbar erector spinae muscles of seated violin players

Burst-like activation of postural muscles has been previously described and plays a crucial role in elucidating the strategies for postural control adopted by the central nervous system (CNS). A spatio-temporal descriptor of surface electromyographic (sEMG) bursts (STB) is proposed and applied to statistically quantify the burst-like activity of the right and left (R-L) lumbar erector spinae muscle of nine seated violinists playing for two hours. The STB signal is the number of pixels of the high density sEMG (HDsEMG) maps simultaneously showing sEMG amplitude above a given threshold. Burst activity was present in all nine subjects. Four of them met four stringent criteria allowing analysis of frequency, duration, and synchronization between the R-L bursts after 0, 15, 30, 60, 120 min of playing. Mean square coherence between STBs of the two muscles was > 0.75 within ⁓1 Hz bandwidth between 2.2 Hz and 4.5 Hz depending on subject. Non-parametric statistics was applied to compare, in time and space, the R-L features of the bursts. The mean STB width was significantly associated primarily to side and secondarily to time and ranged from 100 to 250 ms. The right STB signals led the left (p < 0.02) by 0 - 160 ms.The inverted pendulum composed by the upper body of a seated violinist is controlled in an intermittent way. The erector spinae of the selected subjects were active, on average, for less than 50% of the time. These findings demonstrate a CNS strategy of intermittent back muscle activation presumably aimed to reducing fatigue during hours of playing in seated violinists.

Examination of sex differences in fatigability and neuromuscular responses during continuous, maximal, isometric leg extension

Objective.This study examined sex-related differences in fatigability and neuromuscular responses using surface electromyographic (sEMG) and mechanomyographic (sMMG) amplitude (AMP) and frequency (MPF) during fatiguing, maximal, bilateral isometric leg extensions.Approach.Twenty recreationally active males and females with resistance training experience performed continuous, maximal effort, bilateral isometric leg extensions until their force reduced by 50%. Linear mixed effect models analyzed patterns of force, sEMG, and sMMG AMP and MPF responses in the dominant limb. An independent samples t-test compared time-to-task failure (TTF) between sexes.Main Results.There were no significant differences in TTF between males and females. However, males experienced a greater rate of force loss compared to females. Furthermore, sEMG AMP and MPF and sMMG AMP responses followed similar linear trends for both sexes, while sMMG MPF showed non-linear responses with sex-dependent differences.Significance.These data suggest that although TTF was similar, males had a higher rate of force reduction, likely due to greater absolute strength. Furthermore, despite parallel changes in sEMG AMP and MPF, as well as sMMG AMP, the divergent responses observed in sMMG MPF highlight sex-dependent differences in how males and females experience changes in the firing rates of active motor units during sustained maximal contractions.

Evaluation of fatigue and fatigability in people with Duchenne muscular dystrophy using a dynamic arm support – a pilot study

Background Due to progressive muscle wasting and weakness in patients with Duchenne Muscular Dystrophy (DMD), physical fatigability increases, upper extremity function reduces, which negatively impacts quality of life. Assistive technology such as dynamic arm supports (DAS) may help reduce this fatigability. This study aims to assess whether the novel Yumen ‘EXone’ DAS can reduce upper extremity fatigue and fatigability in DMD patients and healthy controls (HC), both with and without the DAS. Additionally, longitudinal changes in DMD patients were evaluated. Methods Five DMD patients from the Yumen Bionics pioneer program and five HCs participated. Two submaximal tests simulating drinking and reaching were performed for two minutes, each with and without DAS. DMD participants completed these tests twice, at baseline (T0) and after 6-9 months (T1), while HCs completed them once. Physical fatigability was measured by the number of repetitions and changes in surface electromyography (sEMG) amplitude. Subjective fatigue was assessed using the Borg Scale (6-20) Rate of Perceived Exertion (RPE). Results DMD participants generally performed more repetitions with the DAS than without. HCs showed similar or increased repetitions with the DAS. Assessing fatigability with sEMG was difficult due to the compensatory mechanisms used for the tests. Subjective fatigue scores on the Borg Scale were lower with the DAS for both DMD patients and HCs. Conclusion The Yumen ‘EXone’ DAS effectively reduces both fatigue and fatigability in DMD patients and healthy controls. Despite the methodological shortcomings, this research is one of the first studies investigating the impact of DAS on fatigue and fatigability.

Analysis and study on biomarkers of local muscle fatigue caused by repetitive lifting task

BackgroundWork-related musculoskeletal disorders (WMSDs) show a rapid growth trend. It has brought a huge economic burden to the society and become a serious occupational health problem that needs to be solved urgently. This study aimed to analyze the local muscle response under continuous ergonomic load, screen sensitive fatigue-related biomarkers and provide data support for the early prevention of local muscle damage and the exploration of early warning indicators.MethodsThirteen male college student volunteers were recruited to perform simulated repetitive manual lifting tasks in the laboratory. The lifting task was designed for 4 periods which lasted for 12 min in each, and then paused for 3 min for sampling. Local muscle fatigue is assesed by the Rating of perceived exertion (RPE) and the Joint analysis of sEMG spectrum and amplitude (JASA). Elbow venous blood was collected and 14 kinds of biomarkers were analyzed, which included Metabolic markers Ammonia (AMM), Lactic acid (LAC), Creatine kinase (CK), Lactate dehydrogenase (LDH), Cartilage oligomeric matrix protein (COMP), C-telopeptide of collagen I and II (CTX-I, CTX-II) and Calcium ion (Ca2+); Oxidative stress marker Glutathione (GSH); Inflammatory markers C-reaction protein (CRP), Prostaglandin E2 (PG-E2), Interleukin-6 (IL-6) and Tumor necrosis factor α (TNF-α); Pain marker Neuropeptide Y (NPY). Repeated measures analysis of variance (Repeated ANOVA), linear regression analysis, t-test and spearman correlation analysis were used to analyze the data.ResultsBoth subjective and objective fatigue appeared at the same period. Serum AMM, LAC, CK, LDH, COMP, CTX-II, Ca2+ and NPY after fatigue were significantly higher than those before fatigue (p < 0.05). There was a certain degree of correlation between the markers with statistical differences before and after fatigue.ConclusionsMetabolic markers (serum AMM, LAC, CK, LDH, COMP, CTX-II, Ca2+) and pain markers (serum NPY) can reflect local muscle fatigue to a certain extent in repetitive manual lifting tasks. It is necessary to further expand the research on fatigue-related biomarkers in different types of subjects and jobs in the future.

Wireless high-resolution surface facial electromyography mask for discrimination of standardized facial expressions in healthy adults

Wired high resolution surface electromyography (sEMG) using gelled electrodes is a standard method for psycho-physiological, neurological and medical research. Despite its widespread use electrode placement is elaborative, time-consuming, and the overall experimental setting is prone to mechanical artifacts and thus offers little flexibility. Wireless and easy-to-apply technologies would facilitate more accessible examination in a realistic setting. To address this, a novel smart skin technology consisting of wireless dry 16-electrodes was tested. The soft electrode arrays were attached to the right hemiface of 37 healthy adult participants (60% female; 20 to 57 years). The participants performed three runs of a standard set of different facial expression exercises. Linear mixed-effects models utilizing the sEMG amplitudes as outcome measure were used to evaluate differences between the facial movement tasks and runs (separately for every task). The smart electrodes showed specific activation patterns for each of the exercises. 82% of the exercises could be differentiated from each other with very high precision when using the average muscle action of all electrodes. The effects were consistent during the 3 runs. Thus, it appears that wireless high-resolution sEMG analysis with smart skin technology successfully discriminates standard facial expressions in research and clinical settings.

Effects of laptop screen height on neck and shoulder muscle fatigue and spine loading for office workers.

Due to the unfavourable neck-shoulder muscle loads caused by poor posture, the people who use the laptop for a long time may face the risk of neck and shoulder injuries. The purpose of this study investigates the impact of the screen height on the muscle activation of head flexion, neck and shoulder, and the cervical spine torque to provide the favorite screen height for laptop user. Twelve healthy young participants completed a15-minute task of the reading at the four different screen heights. sEMG signals of the splenius capitis (SC) and upper trapezius (UT) were measured and calculated the root mean square (RMS) and mean power frequency (MPF) to determine muscle fatigue. The different height of laptop users was simulated and the forces on the spine of users at different screen heights were analyzed by Jack. Adjusting the height of the laptop screen can effectively reduce head flexion and muscle activity of SC and UT, and has a positive effect on reducing fatigue of SC, but has no significant effect on UT. Adjusting the height of the laptop screen can delay the occurrence of SC muscle fatigue to a certain extent. The joint analysis of sEMG spectrum and amplitude reports that the screen heights of D15 and D45 have the highest and the lowest frequency of fatigue, respectively. At the same time, the moment of spineT1/T2 and spineL4/L5 decrease with the increase of screen height.

Time Course of Neuromuscular Fatigue During Different Resistance Exercise Loadings in Power Athletes, Strength Athletes, and Nonathletes.

Kotikangas, J, Walker, S, Peltonen, H, and Häkkinen, K. Time course of neuromuscular fatigue during different resistance exercise loadings in power athletes, strength athletes, and nonathletes. J Strength Cond Res 38(7): 1231-1242, 2024-Training background may affect the progression of fatigue and neuromuscular strategies to compensate for fatigue during resistance exercises. Thus, our aim was to examine how training background affects the time course of neuromuscular fatigue in response to different resistance exercises. Power athletes (PA, n = 8), strength athletes (SA, n = 8), and nonathletes (NA, n = 7) performed hypertrophic loading (HL, 5 × 10 × 10RM), maximal strength loadings (MSL, 7 × 3 × 3RM) and power loadings (PL, 7 × 6 × 50% of 1 repetition maximum) in back squat. Average power (AP), average velocity (VEL), surface electromyography (sEMG) amplitude (sEMGRMS), and sEMG mean power frequency (sEMGMPF) were measured within all loading sets. During PL, greater decreases in AP occurred from the beginning of SET1 to SET7 and in VEL to both SET4 and SET7 in NA compared with SA (p < 0.01, g > 1.84). During HL, there were various significant group × repetition interactions in AP within and between sets (p < 0.05, ηp2 > 0.307), but post hoc tests did not indicate significant differences between the groups (p > 0.05, g = 0.01-0.93). During MSL and HL, significant within-set and between-set decreases occurred in AP (p < 0.001, ηp2 > 0.701) and VEL (p < 0.001, ηp2 > 0.748) concurrently with increases in sEMGRMS (p < 0.01, ηp2 > 0.323) and decreases in sEMGMPF (p < 0.01, ηp2 > 0.242) in all groups. In conclusion, SA showed fatigue resistance by maintaining higher AP and VEL throughout PL. During HL, PA tended to have the greatest initial fatigue response in AP, but between-group comparisons were nonsignificant despite large effect sizes (g > 0.8). The differences in the progression of neuromuscular fatigue may be related to differing neural activation strategies between the groups, but further research confirmation is required.

Are Surface Electromyography Parameters Indicative of Post-Activation Potentiation/Post-Activation Performance Enhancement, in Terms of Twitch Potentiation and Voluntary Performance? A Systematic Review.

The aim was to identify if surface electromyography (sEMG) parameters are indicative of post-activation potentiation (PAP)/post-activation performance enhancement (PAPE), in terms of twitch potentiation and voluntary performance. Three databases were used in April 2024, with the following inclusion criteria: (a) original research, assessed in healthy human adults, and (b) sEMG parameters were measured. The exclusion criteria were (a) studies with no PAP/PAPE protocol and (b) non-randomized control trials. The following data were extracted: study characteristics/demographics, PAP/PAPE protocols, sEMG parameters, twitch/performance outcomes, and study findings. A modified physiotherapy evidence database (PEDro) scale was used for quality assessment. Fifteen randomized controlled trials (RCTs), with a total of 199 subjects, were included. The M-wave amplitude (combined with a twitch torque outcome) was shown to generally be indicative of PAP. The sEMG amplitudes (in some muscles) were found to be indicative of PAPE during ballistic movements, while a small decrease in the MdF (in certain muscles) was shown to reflect PAPE. Changes in the Hmax/Mmax ratio were found to contribute (temporally) to PAP, while the H-reflex amplitude was shown to be neither indicative of PAP nor PAPE. This review provides preliminary findings suggesting that certain sEMG parameters could be indicative of PAP/PAPE. However, due to limited studies, future research is warranted.

No sex differences in time-to-task failure and neuromuscular patterns of response during submaximal, bilateral, isometric leg extensions.

In general, it has been suggested that females are more fatigue-resistant than males, with the magnitude of difference being most pronounced during low-intensity sustained contractions. However, the mechanisms for the apparent sex difference have not yet been fully elucidated in the literature. This study aimed to examine sex-related differences in fatigability and patterns of neuromuscular responses for surface electromyographic (sEMG) and mechanomyographic (sMMG) amplitude and frequency (MPF) characteristics during a sustained submaximal bilateral, isometric leg extension muscle action. A sample of 20 young recreationally active males and females with previous resistance training experience performed a sustained, submaximal, bilateral isometric leg extension until task failure. Time-to-task failure was compared using a nonparametric bootstrap of the 95% confidence interval for the mean difference between males and females. Additionally, patterns of response for sEMG and sMMG amplitude and MPF of the dominant limb were examined using linear mixed effect models. There were no differences in time-to-task failure between males and females. Additionally, neuromuscular responses revealed similar patterns of responses between males and females. Interestingly, sEMG amplitude and sMMG amplitude and MPF all revealed non-linear responses, while sEMG MPF demonstrated linear responses. These data revealed that time-to-task failure was not different between males and females during sustained submaximal bilateral, isometric leg extension. Interestingly, the parallel, non-linear, increases in sEMG and sMMG amplitude may indicate fatigue induced increases in motor unit recruitment, while the parallel decreases in sMMG MPF may be explained by the intrinsic properties of later recruited motor units, which may have inherently lower firing rates than those recruited earlier.

Are Diminishing Potentiation and Large Extensor Moments the Cause for the Occurrence of the Sticking Region in Maximum Free-Weight Barbell Back Squats among Resistance-Trained Males?

This study compared the kinematics, surface electromyography (sEMG) and kinetics among isometric squats performed at 10 different heights of the upward part and a one-repetition maximum (1-RM) squat. Eleven males (age: 27.5 ± 3.4 years, body mass: 84.9 ± 8.1 kg, body height: 1.79 ± 0.06 m, 1-RM squat: 152.2 ± 20.55 kg) took part in this study. It was found that force output was lowest in the sticking region at around the event of peak deceleration for the 1-RM trial with force output at 2179 ± 212 N. For the isometric trial, the lowest force output occurred at the lowest barbell height (1735 ± 299 N). In addition, for the 1-RM condition hip extension moments peaked at the first four barbell heights (6.5-6.2 Nm/kg) representing the pre-sticking and the sticking region before significantly decreasing during the events representing the post-sticking region. Additionally, the sEMG amplitude peaked for the hip extensors at the barbell heights corresponding to the post-sticking region. Moreover, the sEMG amplitude was significantly higher for the 1-RM condition for all hip extensors, vastus lateralis, and calf muscles (F ≥ 2.7, p ≤ 0.01, ηp2 ≥ 0.25). Therefore, we suggest that the sticking region occurs because of reduced force output in the pre-sticking and the sticking region in back squats among resistance-trained males. The reduced force output is probably a combination of suboptimal internal moment arms, length-tension relationships of the gluteus maximus, hamstring and vastii muscles in the pre-sticking and sticking regions to overcome the large extensor moments together with diminishing potentiation from the pre-sticking to the sticking region.

Extrinsic Laryngeal Muscle Activity With Different Diameters and Water Depths in a Semi-Occluded Vocal Tract Exercise.

Surface electromyography (sEMG) has been used to evaluate extrinsic laryngeal muscle activity during swallowing and phonation. In the current study, sEMG amplitudes were measured from the infrahyoid and suprahyoid muscles during phonation through a tube submerged in water. The sEMG amplitude values measured from the extrinsic laryngeal muscles and the electroglottographic contact quotient (CQ) were obtained simultaneously from 62 healthy participants (31 men, 31 women) during phonation through a tube at six different depths (2, 4, 7, 10, 15, and 20 cm) while using two tubes with different diameters (1 and 0.5 cm). With increasing depth, the sEMG amplitude for the suprahyoid muscles increased in men and women. However, sEMG amplitudes for the infrahyoid muscles increased significantly only in men. Tube diameter had a significant effect on the suprahyoid sEMG amplitudes only for men, with higher sEMG amplitudes when phonating with a 1.0-cm tube. CQ values increased with submerged depth for both men and women. Tube diameter affected results such than CQ values were higher for men when using the wider tube and for women with the narrower tube. Vocal fold vibratory patterns changed with the depth of tube submersion in water for both men and women, but the patterns of muscle activation differed between the sexes. This suggests that men and women use different strategies when confronted with increased intraoral pressure during semi-occluded vocal tract exercises. In this study, sEMG provided insight into the mechanism for differences between vocally normal individuals and could help detect compensatory muscle activation during tube phonation in water for people with voice disorders.

The effect of foot somatosensory loss in postural control during Functional reach test in patients with diabetic polyneuropathy: A controlled study

BackgroundIn patients with diabetic polyneuropathy (DPN), differences in postural control due to losing the lower limb somatosensory information were reported. However, it is still unclear by which mechanisms the dynamic postural instability is caused. ObjectivesThis study aimed to investigate postural control differences and neuromuscular adaptations resulting from foot somatosensory loss due to DPN. MethodsIn this controlled cross-sectional study, fourteen DPN patients and fourteen healthy controls performed the Functional Reach Test (FRT) as a dynamic task. The postural control metrics were simultaneously measured using force plate, motion capture system, and surface electromyography (sEMG). The main metrics including reach length (FR), FR to height ratio (FR/H), displacement of CoM and CoP, moment arm (MA), and arch height ratio. Also, kinematic (range of motion of ankle, knee, and hip joints), and sEMG metrics (latencies and root mean square amplitudes of ankle and hallux muscles) were measured. To compare variables between groups, the independent sample T-test for (normally distributed) and the Mann-Whitney U test (non-normally distributed) were used. ResultsThe subjects' reach length (FR), FR to height ratio, absolute MA, and displacement of CoM were significantly shorter than controls, while displacement of CoP was not significant. Arch height ratio was found significantly lower in DPN patients. We observed that CoM was lagging CoP in patients (MA = + 0.89) while leading in controls (MA = -1.60). Although, the muscles of patients showed significantly earlier activation, root mean square sEMG amplitudes were found similar. Also, DPN patients showed significantly less hip flexion, knee extension, and ankle plantar flexion. ConclusionsThis study presented that decreasing range of motion at lower limbs’ joints and deterioration in foot function caused poor performance at motor execution during FRT in DPN patients.

Unsupervised neural decoding for concurrent and continuous multi-finger force prediction

Reliable prediction of multi-finger forces is crucial for neural-machine interfaces. Various neural decoding methods have progressed substantially for accurate motor output predictions. However, most neural decoding methods are performed in a supervised manner, i.e., the finger forces are needed for model training, which may not be suitable in certain contexts, especially in scenarios involving individuals with an arm amputation. To address this issue, we developed an unsupervised neural decoding approach to predict multi-finger forces using spinal motoneuron firing information. We acquired high-density surface electromyogram (sEMG) signals of the finger extensor muscle when subjects performed single-finger and multi-finger tasks of isometric extensions. We first extracted motor units (MUs) from sEMG signals of the single-finger tasks. Because of inevitable finger muscle co-activation, MUs controlling the non-targeted fingers can also be recruited. To ensure an accurate finger force prediction, these MUs need to be teased out. To this end, we clustered the decomposed MUs based on inter-MU distances measured by the dynamic time warping technique, and we then labeled the MUs using the mean firing rate or the firing rate phase amplitude. We merged the clustered MUs related to the same target finger and assigned weights based on the consistency of the MUs being retained. As a result, compared with the supervised neural decoding approach and the conventional sEMG amplitude approach, our new approach can achieve a higher R2 (0.77 ± 0.036 vs. 0.71 ± 0.11 vs. 0.61 ± 0.09) and a lower root mean square error (5.16 ± 0.58 %MVC vs. 5.88 ± 1.34 %MVC vs. 7.56 ± 1.60 %MVC). Our findings can pave the way for the development of accurate and robust neural-machine interfaces, which can significantly enhance the experience during human-robotic hand interactions in diverse contexts.

Ischemic preconditioning increases spinal excitability and voluntary activation during maximal plantar flexion contractions in men.

The enigmatic benefits of acute limb ischemic preconditioning (IP) in enhancing muscle force and exercise performance have intrigued researchers. This study sought to unravel the underlying mechanisms, focusing on increased neural drive and the role of spinal excitability while excluding peripheral factors. Soleus Hoffmann (H)-reflex /M-wave recruitment curves and unpotentiated supramaximal responses were recorded before and after IP or a low-pressure control intervention. Subsequently, the twitch interpolation technique was applied during maximal voluntary contractions to assess conventional parameters of neural output. Following IP, there was an increase in both maximum normalized force and voluntary activation (VA) for the plantar flexor group, with negligible peripheral alterations. Greater benefits were observed in participants with lower VA levels. Despite greater H-reflex gains, soleus volitional (V)-wave and sEMG amplitudes remained unchanged. In conclusion, IP improves muscle force via enhanced neural drive to the muscles. This effect appears associated, at least in part, to reduced presynaptic inhibition and/or increased motoneuron excitability. Furthermore, the magnitude of the benefit is inversely proportional to the skeletal muscle's functional reserve, making it particularly noticeable in under-recruited muscles. These findings have implications for the strategic application of the IP procedure across diverse populations.

Impact of Ergonomics on Muscle Fatigue During Surgical Drilling Using Surface Electromyography.

To investigate the relationship between ergonomic positions and electromyographic muscle activity during otologic drilling. Cross-over experimental trial. Tertiary Academic Medical Center. Surgeon participants were tasked with delicate eggshell drilling in 3 different seated positions: "neutral,""slouched,"and "craned." Surface electromyography (sEMG) sensors recorded the amplitude and frequency of muscle activity. The joint analysis of spectrum and amplitude (JASA) method, which combines temporal trends in frequency and amplitude, was used to identify trials that exhibited patterns of fatigue. The sEMG amplitude and frequency responses demonstrated wide temporal changes. In a majority of experiments, amplitude increased over the course of the experiment, while frequency remained more stable. On analysis of variance testing, only the mean frequency of the deltoid differed significantly between postures (P = .02). Under the JASA framework, external carpi radialis and upper trapezius experienced fatigue in nearly half of the trials regardless of position (47% vs 49%). The upper trapezius demonstrated fatigue during 46% and 69% of the "craned" and "slouched" trials, respectively, compared to just 31% of the "neutral" trials. Fewer attendings demonstrated upper trapezius fatigue compared to trainees (33% vs 62%). Female surgeons experienced fatigue in more trials than male counterparts (73% vs 25%). This study highlights a first step in quantifying the relationship between operating postures and muscle fatigue. Results suggest that specific muscle groups are more susceptible to fatigue; gender and experience may also impact muscle activity.

A controlled clinical trial investigating the effects of stretching and compression exercises on electromyography of calf muscles in chronic LBP patients with a deep gluteal syndrome

BackgroundIn deep gluteal syndrome (DGS), the piriformis muscle could impinge the sciatic nerve. The FAIR (flexion adduction internal rotation) test is a provocation test used to identify sciatic nerve irritation caused by this muscle. Compression and stretching exercises are usually prescribed to treat this syndrome. The aim of this study was to compare the effects of these two treatments on surface electromyography (sEMG) of the gastrocnemius and tibialis anterior in patients with low back pain (LBP) and DGS.Materials and methodsForty-five participants were allocated to three groups of stretching exercise, compression or control. In addition to 15 min of heat and 15 min of electrical nerve stimulation for pain relief, participants in the compression exercise (CE) group received self-compression exercise, those in the stretching exercise (SE) group received self-stretching exercise and those in the control group received no extra interventions. For the two intervention groups, three sets of two minutes of exercise with two minutes of rest in between were applied. The sEMG amplitude values of the gastrocnemius and tibialis anterior muscles of the affected buttock side of any one group while performing the FAIR test were compared to the others. Pain and disability were assessed and the changes were compared between the two groups.ResultsAfter the intervention period, no group demonstrated a change in the sEMG of the gastrocnemius or tibialis anterior muscles (p > 0.05). There was no difference in the change in this variable between groups (Mean difference (95% CI) of gastrocnemius was ranged over= -4.04 to 7.72 (-19.44 to 23.14); p = 0.603); (Mean difference (95% CI) of tibialis anterior muscles was ranged from − 2.44 to -6.43 (-18.28 to 9.31); p = 0.550).; Pain and disability also decreased significantly in all three study groups (p < 0.05). However, only the disability of patients who performed stretching exercises improved compared to the compression exercise group (Mean difference (95% CI) = -12.62 (-20.41 to -4.38); p = 0.009).ConclusionNeither stretching nor compression exercises altered the sEMG of the gastrocnemius and tibialis anterior muscles in patients with DGS. Furthermore, performing stretching exercises improved disability compared to the other interventions.Trial registrationThe trial was retrospectively registered in the Iranian Registry of Clinical Trials (www.irct.ir) on 10/01/2017 as IRCT201604178035N4. URL of the record: https://en.irct.ir/trial/8473.

Individuals with chronic ankle instability show altered regional activation of the peroneus longus muscle during ankle eversion.

Individuals with chronic ankle instability (CAI) present muscular weakness and potential changes in the activation of the peroneus longus muscle, which likely explains the high recurrence of ankle sprains in this population. However, there is conflicting evidence regarding the role of the peroneus longus activity in CAI, possibly due to the limited spatial resolution of the surface electromyography (sEMG) methods (i.e., bipolar sEMG). Recent studies employing high-density sEMG (HD-sEMG) have shown that the peroneus longus presents differences in regional activation, however, it is unknown whether this regional activation is maintained under pathological conditions such as CAI. This study aimed to compare the myoelectric activity, using HD-sEMG, of each peroneus longus compartment (anterior and posterior) between individuals with and without CAI. Eighteen healthy individuals (No-CAI group) and 18 individuals with CAI were recruited. In both groups, the center of mass (COM) and the sEMG amplitude at each compartment were recorded during ankle eversion at different force levels. For the posterior compartment, the sEMG amplitude of CAI group was significantly lower than the No-CAI group (mean difference = 5.6% RMS; 95% CI = 3.4-7.6; p = 0.0001). In addition, it was observed a significant main effect for group (F1,32 = 9.608; p = 0.0040) with an anterior displacement of COM for the CAI group. These findings suggest that CAI alters the regional distribution of muscle activity of the peroneus longus during ankle eversion. In practice, altered regional activation may impact strengthening programs, prevention, and rehabilitation of CAI.