Assessment Of Muscle Fatigue Research Articles

Design Validation of a Low-Cost EMG Sensor Compared to a Commercial-Based System for Measuring Muscle Activity and Fatigue.

Electromyography (EMG) sensors have been used for measuring muscle signals and for diagnosing neuromuscular disease. Available commercial EMG sensor are expensive and not easily available for individuals. The aim of the study is to validate our designed low-cost sensor against a well-known commercial system for measuring muscle activity and fatigue assessment. The evaluation of the designed system was done through a series of dynamic exercises performed by volunteers. Our low-cost EMG sensor and the commercially available system were placed on the vastus lateralis muscle to concurrently record the signal in a maximum voluntary contraction (MVC). The signal analysis was done using two validation indicators: Spearman’s correlation, and intra-class cross correlation on SPSS 26.0 version. For the muscle fatigue assessment, the root mean square (RMS), mean absolute value (MAV) and mean frequency (MNF) indicators were used. The results at the peak and mean level muscle contraction intensity were computed. The relative agreement for the two systems was excellent at peak level muscle contraction range (ICC 0.74–0.92), average 0.83 and mean level muscle contraction intensity range (ICC 0.65–0.85) with an average of 0.74. The Spearman’s correlation average was 0.76 with the range of (0.71–0.85) at peak level contraction, whiles the mean level contraction average was 0.71 at a range of (0.62–0.81). In determining muscle fatigue, the RMS and MAV showed increasing values in the time domain, while the MEF decreased in the frequency domain. Overall, the results indicated a good to excellent agreement of the two systems and confirmed the reliability of our design. The low-cost sensor also proved to be suitable for muscle fatigue assessment. Our designed system can therefore be implemented for rehabilitation, sports science, and ergonomics.

Investigation of muscle fatigue during on-water rowing using surface EMG.

In this work, four different algorithms (fast Fourier transform FFT, short-time Fourier transform STFT, continuous wavelet transform CWT, and instantaneous frequency IF) for calculating median frequency (MDF) from surface EMG signals were investigated for studying muscle fatigue during a on-water rowing training. The study protocol included 5 consecutive parts with increasing stroke rate. Six athletes participated in the study aged 36.6+-14.6 years and a rowing experience of 6 to 35 years. We considered eight muscles: biceps brachii right, biceps brachii left, latissimus dorsi right, latissimus dorsi left, erector spinae right, erector spinae left, rectus femoris and biceps femoris. By applying Friedmann test, we found a significant difference in MDF behavior between algorithms in assessing muscle fatigue . Correlation analyses showed significant correlations between muscle activity duration tact and MDF, which differs for the four considered algorithms and should be taken into account in further experiments. With CWT showing the smallest correlation to tact it might be more robust against time window variations. Our study provides a basis for the development of improved methods for more robust, non-invasive, and continuous detection of muscle fatigue in experiments with dynamic on-water rowing study designs.

Assessment of Muscle Fatigue Using EMG under Long Duration and High Intensity Fatigue Condition

Evaluation of local muscle fatigue has been conducted over past decades to investigate the process of fatigue accumulation and to reduce effect of fatigue in EMG field. The purpose of this study was to investigate fatigue in isotonic contractions, which can inflict the same fatigue on the subject during dynamic contractions. Local muscle fatigue was measured by changing the load level and exercise time in dumbbell curl comprising isotonic contractions through power spectrum changes. Five healthy males and five healthy females performed dumbbell curls with 1 kg load for two minutes, and on other days when no fatigue occurred due to the previous exercise, performed for one minute with a 2 kg load. The muscle fatigue was estimated by median frequency before and after fatigue, the decrease was greater than in the trial wherein a load of 2 ㎏ was applied for one minute than in the trial where a load of 1 kg was applied for two minutes for the females. The decrease in the median frequency is quantitative data indicated by the slowing of the motor unit actional potential (MUAP), suggesting exercise intensity is more sensitive to the slowing of the MUAP than the exercise duration.

Evaluation of Muscle Fatigue and Determination of Risk Factors of Musculoskeletal Disorders Among Saffron Harvesters in Gonabad in 2017

Aims Musculoskeletal disorders (MSDs) are common in farmers due to the high workload in agriculture. Because several factors, such as physical, personal, and psychological factors in saffron harvesters can influence persons’ physical conditions and expose them to the risk of MSDs, the present study aimed to investigate muscle fatigue and determine the prevalence of MSDs and related factors among Gonabad saffron harvesters. Methods & Materials This cross-sectional study was performed on 84 saffron harvesters in Gonabad city, Iran. Data collection tools included a standard Nordic questionnaire to assess the prevalence of MSDs and the muscle fatigue assessment (MFA) method to assess body muscle fatigue. Finally, the data were analyzed using SPSS software, version 20. Findings The prevalence of MSDs in saffron harvesters in the shoulder, wrist, ankle, upper back, lower back, elbow, neck, thigh, and knee was 91.7, 90.5, 92.9, 8.48, 50, 88.1, 15.5, 50, and 47.6%, respectively. The results of the MFA evaluation also showed that the risk of muscle fatigue in the neck, right wrist, and right arm is very high in 98.8%, 49.4%, and 36.5% of employees, respectively. There was a significant relationship between MSDs in the past 12 months and age, sex, medical history, and working hours, and between muscle fatigue and age, smoking, and exercise (P<0.05). Conclusion The highest prevalence of symptoms of MSDs was in the shoulder, wrist, and ankle areas. Due to the significant prevalence of MSDs among saffron harvesters, it is necessary to consider ergonomic interventions, soft movements at regular intervals, and raising awareness in the form of educational programs.

Validity of using perceived exertion to assess muscle fatigue during resistance exercises.

BackgroundThe rating of perceived exertion (RPE) is correlated with physiological variables. The purpose of this study was to assess the validity of using the Borg CR-10 scale and velocity to predict muscle fatigue assessed by surface electromyography during single joint resistance exercises.MethodsFifteen healthy males underwent different fatigue levels of unilateral elbow flexion (EF) and knee extension (KE), consisting of low, medium, and high volumes at 65% of their one-repetition maximum. The RPEs, spectral fatigue index (SFI), and mean velocity of the experimental exercises were assessed throughout the trials.ResultsSignificant differences in overall RPE (p < 0.001) and average SFI (p < 0.001) were observed between the conditions in both exercises. Significant changes in RPE and SFI (p < 0.001) were observed throughout the EF, whereas a SFI increase (p < 0.001) was only observed at the end point of KE. Multiple regression analyses revealed two significant models (p < 0.001) for the prediction of muscle fatigue during EF (R2 = 0.552) and KE (R2 = 0.377).ConclusionsMuscle fatigue resulted in similar increases in perceptual responses, demonstrating that RPE is useful for assessing fatigue when resistance exercise is performed. However, velocity changes may not reflect muscle fatigue correctly when exercise is no longer performed in an explosive manner. We recommend combining RPE responses with velocity changes to comprehensively assess muscle fatigue during clinical and sports situations.

Assessment of muscle activity and fatigue during laparoscopic surgery.

Cumulative musculoskeletal stress during operative procedures can contribute to the development of chronic musculoskeletal injury among surgeons. This is a concern in laparoscopic specialties where trainees may incur greater risk by learning poor operative posture or technique early in training. This study conducted an initial investigation of the physical stress encountered during the conduct of foregut laparoscopic surgery. Subjects were divided into two groups based on their surgical experience level, high experience (HE), consisting of two attending surgeons, and low experience (LE), consistingof two fellow surgeons and a surgical chief resident. Nine distinct foregut laparoscopic procedures were observed for data collection within these groups. Electromyographic (EMG) activity was collected at the bilateral neck, shoulders, biceps, triceps, and lower back for each procedure. Physical workload was measured using percent reference voluntary contractions (%RVC) for each surgeon's muscle activities. Fatigue development was assessed using the median frequency of EMG data between two consecutive cases. Subjects completed a NASA-TLX survey when surgery concluded. LE surgeons experienced higher levels of %RVC in the lower back muscles compared to HE surgeons. LE fatigue level was also higher than HE surgeons across most muscle groups. A decrease in median frequency in six of the ten muscle groups after performing two consecutive cases, the largest decrements being in the biceps and triceps indicated fatigue development across consecutive cases for both surgeon groups. Surgeons developed fatigue in consecutive cases while performing minimally invasive surgery (MIS). HE surgeons demonstrated a lower overall physical workload while also demonstrating different patterns in muscle work. The findings from this study can be used to inform further ergonomic studies and the data from this study can be used to develop surgical training programs focused on the importance of surgeon ergonomics and minimizing occupational injury risk.

Modeling and Validation of Fatigue and Recovery of Muscles for Manual Demolition Tasks.

Manual demolition tasks are heavy, physically demanding tasks that could cause muscle fatigue accumulation and lead to work-related musculoskeletal disorders (WMSDs). Fatigue and recovery models of muscles are essential in understanding the accumulation and the reduction in muscle fatigue for forceful exertion tasks. This study aims to explore the onset of muscle fatigue under different work/rest arrangements during manual demolition tasks and the offset of fatigue over time after the tasks were performed. An experiment, including a muscle fatigue test and a muscle fatigue recovery test, was performed. Seventeen male adults without experience in demolition hammer operation were recruited as human participants. Two demolition hammers (large and small) were adopted. The push force was either 20 or 40 N. The posture mimicked that of a demolition task on a wall. In the muscle fatigue test, the muscle strength (MS) before and after the demolition task, maximum endurance time (MET), and the Borg category-ratio-10 (CR-10) ratings of perceived exertion after the demolition task were measured. In the muscle fatigue recovery test, MS and CR-10 at times 1, 2, 3, 4, 5, and 6 min were recorded. Statistical analyses were performed to explore the influence of push force and the weight of the tool on MS, MET, and CR-10. Both muscle fatigue models and muscle fatigue recovery models were established and validated. The results showed that push force affected MET significantly (p < 0.05). The weight of the tool was significant (p < 0.05) only on the CR-10 rating after the first pull. During the muscle fatigue recovery test, the MS increase and the CR-10 decrease were both significant (p < 0.05) after one or more breaks. Models of MET and MS prediction were established to assess muscle fatigue recovery, respectively. The absolute (AD) and relative (RD) deviations of the MET model were 1.83 (±1.94) min and 34.80 (±31.48)%, respectively. The AD and RD of the MS model were 1.39 (±0.81) N and 1.9 (±1.2)%, respectively. These models are capable of predicting the progress and recovery of muscle fatigue, respectively, and may be adopted in work/rest arrangements for novice workers performing demolition tasks.

Assessment of Muscle Fatigue Based on Motor Unit Firing, Muscular Vibration and Oxygenation via Hybrid Mini-Grid sEMG, MMG, and NIRS Sensing

It is vital to measure muscular fatigue for human-machine interaction (HMI) and avoiding muscle impairment. This paper presents a novel approach to comprehensively evaluate muscle fatigue through the fusion of mini-grid surface electromyography (sEMG), mechanomyography (MMG) and near-infrared spectroscopy (NIRS). A hybrid mini-grid sEMG, MMG and NIRS sensor system was developed, forming an instrument to measure motor unit action potential trains (MUAPt), low-frequency myofiber vibration and oxygen metabolism. Muscle fatigue induced experiment was performed via a sustained isometric contraction at 50% of maximal voluntary contraction (MVC) force with ten subjects. MUAPts were decomposed from the four-channel array of sEMG signals, and the firing rate of specific MUs was calculated to measure fatigue process. Furthermore, root mean square (RMS) and median frequency (MDF) of sEMG/MMG, blood volume (BV) and muscle oxygenation (&#x25B3;HbO₂) extracted from NIRS, were proposed as fatigue metrics. The variation and correlation analysis among fatigue metrics provided a detailed and reliable physiological assessment on muscle fatigue, gaining a synthetical understanding of muscle fatigue mechanisms. The outcomes of this study have great potential applications in sports, clinical diagnosis and HMI.

Ultrasound Echogenicity-based Assessment of Muscle Fatigue During Functional Electrical Stimulation.

The rapid onset of muscle fatigue during functional electrical stimulation (FES) is a major challenge when attempting to perform long-term periodic tasks such as walking. Surface electromyography (sEMG) is frequently used to detect muscle fatigue for both volitional and FES-evoked muscle contraction. However, sEMG contamination from both FES stimulation artifacts and residual M-wave signals requires sophisticated processing to get clean signals and evaluate the muscle fatigue level. The objective of this paper is to investigate the feasibility of computationally efficient ultrasound (US) echogenicity as a candidate indicator of FES-induced muscle fatigue. We conducted isometric and dynamic ankle dorsiflexion experiments with electrically stimulated tibialis anterior (TA) muscle on three human participants. During a fatigue protocol, we synchronously recorded isometric dorsiflexion force, dynamic dorsiflexion angle, US images, and stimulation intensity. The temporal US echogenicity from US images was calculated based on a gray-scaled analysis to assess the decrease in dorsiflexion force or motion range due to FES-induced TA muscle fatigue. The results showed a monotonic reduction in US echogenicity change along with the fatigue progression for both isometric (R2 =0.870±0.026) and dynamic (R2 =0.803±0.048) ankle dorsiflexion. These results implied a strong linear relationship between US echogenicity and TA muscle fatigue level. The findings indicate that US echogenicity may be a promising computationally efficient indicator for assessing FES-induced muscle fatigue and may aid in the design of muscle-in-the-loop FES controllers that consider the onset of muscle fatigue.

Impaired Muscle Mitochondrial Function in Familial Partial Lipodystrophy.

Familial partial lipodystrophy (FPL), Dunnigan variety is characterized by skeletal muscle hypertrophy and insulin resistance besides fat loss from the extremities. The cause for the muscle hypertrophy and its functional consequences is not known. To compare muscle strength and endurance, besides muscle protein synthesis rate between subjects with FPL and matched controls (n = 6 in each group). In addition, we studied skeletal muscle mitochondrial function and gene expression pattern to help understand the mechanisms for the observed differences. Body composition by dual-energy X-ray absorptiometry, insulin sensitivity by minimal modelling, assessment of peak muscle strength and fatigue, skeletal muscle biopsy and calculation of muscle protein synthesis rate, mitochondrial respirometry, skeletal muscle transcriptome, proteome, and gene set enrichment analysis. Despite increased muscularity, FPL subjects did not demonstrate increased muscle strength but had earlier fatigue on chest press exercise. Decreased mitochondrial state 3 respiration in the presence of fatty acid substrate was noted, concurrent to elevated muscle lactate and decreased long-chain acylcarnitine. Based on gene transcriptome, there was significant downregulation of many critical metabolic pathways involved in mitochondrial biogenesis and function. Moreover, the overall pattern of gene expression was indicative of accelerated aging in FPL subjects. A lower muscle protein synthesis and downregulation of gene transcripts involved in muscle protein catabolism was observed. Increased muscularity in FPL is not due to increased muscle protein synthesis and is likely due to reduced muscle protein degradation. Impaired mitochondrial function and altered gene expression likely explain the metabolic abnormalities and skeletal muscle dysfunction in FPL subjects.

Detection of muscle fatigue caused by repeated posterior tongue lift movement from neck surface EMG: a pilot study.

Fatigue is an important factor for muscle strengthening in rehabilitation medicine. Frequency analysis has been regarded as the gold standard for muscle fatigue assessment in surface electromyography (EMG). However, there are no experiments quantifying fatigue with grouped discharge (GD), which is one of the historical phenomena observed in patients having fatigue, by using high sampling rate recording of EMG. To investigate the effect of fatigue, which is induced by repeated posterior tongue lift movement (TLM), on the occurrence of GD peaks, thus, to provide possible basis as a parameter for future fatigue evaluation. Nineteen healthy adults (9men and 10 women) participated in this study. The muscle fatigue protocol consisted of repetitive posterior TLM and maximum voluntary contractions (MVC). Bilateral N-EMG (Neck surface EMG for measuring the muscle activity of the posterior tongue) was recorded. Subjective tongue fatigue at the end of the protocol was significantly higher than at beginning throughout the muscle fatigue protocol (p<.01). The frequency of occurrence of GD peaks was 0.9±1.2 (per second) at the baseline in 33 of 38subject sides, and significantly increased depending on fatigue progression (p<.01). It was shown that fatigue due to repetitive posterior tongue lifting resulted in significant increase in the frequency of occurrence of GD peaks. Especially, the nature of GD, showing very few occurrences at non-fatigue condition, might work as an advantageous property for its use in future absolute evaluation of fatigue phenomena.

Effects of Muscle Fatigue and Recovery on Complexity of Surface Electromyography of Biceps Brachii.

This study aimed to investigate the degree of regularity of surface electromyography (sEMG) signals during muscle fatigue during dynamic contractions and muscle recovery after cupping therapy. To the best of our knowledge, this is the first study assessing both muscle fatigue and muscle recovery using a nonlinear method. Twelve healthy participants were recruited to perform biceps curls at 75% of the 10 repetitions maximum under four conditions: immediately and 24 h after cupping therapy (−300 mmHg pressure), as well as after sham control (no negative pressure). Cupping therapy or sham control was assigned to each participant according to a pre-determined counter-balanced order and applied to the participant’s biceps brachii for 5 min. The degree of regularity of the sEMG signal during the first, second, and last 10 repetitions (Reps) of biceps curls was quantified using a modified sample entropy (Ems) algorithm. When exercise was performed immediately or 24 h after sham control, Ems of the sEMG signal showed a significant decrease from the first to second 10 Reps; when exercise was performed immediately after cupping therapy, Ems also showed a significant decrease from the first to second 10 Reps but its relative change was significantly smaller compared to the condition of exercise immediately after sham control. When exercise was performed 24 h after cupping therapy, Ems did not show a significant decrease, while its relative change was significantly smaller compared to the condition of exercise 24 h after sham control. These results indicated that the degree of regularity of sEMG signals quantified by Ems is capable of assessing muscle fatigue and the effect of cupping therapy. Moreover, this measure seems to be more sensitive to muscle fatigue and could yield more consistent results compared to the traditional linear measures.

The assessment of muscle fatigue in orthopedic surgeons, by comparing manual versus automated broaching in simulated total hip arthroplasty.

Total hip arthroplasty procedures are physically demanding for surgeons. Repetitive mallet swings to impact a surgical handle (impactions), can lead to muscle fatigue, discomfort, and injuries. The use of an automated surgical hammer may reduce fatigue and increase surgical efficiency. The aim of this study was to compare the effect of repeated manual and automated impactions on the user's muscle activation, by means of surface electromyography. Surface electromyography signals were recorded from eight muscles of seven (n = 7) orthopedic surgeons during repetitions of manual and automated impactions, to reach the same surgical outcome (broaching depth). Qualitative data was also captured to track the perceived fatigue and preferences of impaction modalities after completion of impaction tasks. Time to complete tasks, muscle activation, and muscle fatigue were quantified. Results showed a significant decrease in time required to reach the same broaching depth for the automated method compared to manual impactions (p = 0.001). A reduction in muscle fatigue and activation of right Brachioradialis muscle was observed during automated impactions (p = 0.018). A significant difference in fatigue was observed, with lower level of fatigue during automated impactions (p = 0.001). These results suggest that an automated surgical workflow might reduce the exposure to the impaction task and, therefore, muscle fatigue, with a reduced activation of the most engaged muscles. The study suggests that the burden on the user can be reduced by a change in the surgical methodology to perform broaching in total hip arthroplasty, which could potentially benefit surgical efficiency and reduce the risk of fatigue-based errors during a procedure.

Assessment of Isometric Muscle Exertion in Short-term Considering Task-rest Schedule

Numerous workers experience occupational diseases, especially musculoskeletal disorders, due to various physical, psychological, and individual factors. Among known risk factors for musculoskeletal disorders, work-rest patterns, and muscle fatigue are to be named. Assessment of muscle fatigue plays an important role, leading to a proper design for a work-rest program. This study was aimed to investigate isometric muscle strength in Iranian workers during repetitive activities based on gender and rest time. It has been attempted to present a model for isometric muscle strength. In a laboratory experiment, 31 students comprised of 19 males and 12 females participated, and muscle strength was recorded by a dynamometer. Minitab software results analysis proved that females' upper body muscles showed a higher level of resistance to fatigue rather than males. Furthermore, tests' results for each individual were more in line with cubic regression so that four models with a high R-Sq index (at least 94.4%) and high R-Sq (adj) index (at least 77.8%) were presented to predict isometric muscle strength in short-run. Finally, it has been suggested to use male workers for repetitive activities with a high workload and enough rest time and use female workers for repetitive activities with low workload and high frequency.

Analysis of Work Posture Using the Muscle Fatigue Assessment (MFA) and Novel Ergonomic Postural Assessment (NERPA)

A company needs to know each employee's ability to reduce accidents that happen to workers due to a lack of study on ergonomic principles. The research was conducted at a construction company producing paving blocks in Kediri. The paving production capacity at the company is 1000 paving/day. In 2017, three work accidents were caused by the fast pace of workers reaching the tired phase while working. Pulling, lifting, and putting down in carrying weighty loads and the repetition frequency of intense activities trigger stress on body parts that affect the worker's performance. The purpose of this study is to assess and provide recommendations for improvements in work activities that have a hazardous risk value based on the MFA and NERPA assessment methods. The research on the MFA method shows that activities with dangerous risk (high/very high) were in transportation activities. For the NERPA method, activities with dangerous risks were in 3 activities at the finishing work station with a final score of 7. Recommendations for improvement are work posture improvement, physical environment improvement, and work facilities.

Immediate and Delayed Effects of Cupping Therapy on Reducing Neuromuscular Fatigue.

Cupping therapy has been popular in elite athletes in recent years. However, the effect of cupping therapy on reducing muscle fatigue has not been investigated. The purpose of this study was to investigate the immediate and delayed effects of cupping therapy on reducing biceps brachii fatigue during biceps curls. Twelve healthy untrained participants were recruited for this repeated-measures study. Cupping therapy (–300 mmHg pressure for 5 min) and sham control (no negative pressure for 5 min) were applied after biceps fatigue induced by performing repeated biceps curls at 75% of the 10 repetitions of maximum of the non-dominant hand. Surface electromyography (EMG) with spectral analyses [mean frequency (MNF), median frequency (MDF), and spectral moments ratio (SMR)] were used to assess muscle fatigue during the fatigue task. EMG signals during the first 10 repetitions and the last 10 repetitions of biceps curls were used to assess neuromuscular fatigue. There were significant decreases in MNF and MDF and a significant increase in SMR immediately and 24 h after the sham control (no intervention). When comparing the MNF, MDF, and SMR after cupping therapy to the sham control, there was no significant immediate effect on reducing muscle fatigue. However, there was a significant delayed effect on improving recovery following fatigue for the cupping therapy compared to the sham control (MNF changes: sham 0.87 ± 0.02 vs. cupping 0.91 ± 0.02, p < 0.05; MDF changes sham: 0.85 ± 0.03 vs. cupping: 0.91 ± 0.02, p < 0.05; SMR changes: sham 1.89 ± 0.15 vs. cupping 1.58 ± 0.13, p < 0.05). The findings of this study demonstrate that there is a time effect of cupping therapy for reducing muscle fatigue. Cupping therapy is effective on reducing biceps brachii muscle fatigue after 24 h.

VARIATION OF INSTANTANEOUS SPECTRAL CENTROID ACROSS BANDS OF SURFACE ELECTROMYOGRAPHIC SIGNALS

Surface electromyography (sEMG) is a technique which noninvasively acquires the electrical activity of muscles and is widely used for muscle fatigue assessment. This study attempts to characterize the dynamic muscle fatiguing contractions with frequency bands of sEMG signals and a geometric feature namely the instantaneous spectral centroid (ISC). The sEMG signals are acquired from biceps brachii muscle of fifty-eight healthy volunteers. The frequency components of the signals are divided into low frequency band (10-45Hz), medium frequency band (55-95Hz) and high frequency band (95-400Hz). The signals associated with these bands are subjected to a Hilbert transform and analytical shape representation is obtained in the complex plane. The ISC feature is extracted from the resultant shape of the three frequency bands. The results show that this feature can differentiate the muscle nonfatigue and fatigue conditions (p&lt;0.05). It is found the values of ISC is lower in fatigue conditions irrespective of frequency bands. It is also observed that the coefficient of variation of ISC in the low frequency band is less and it demonstrates the ability of handling inter-subject variations. Therefore, the proposed geometric feature from the low frequency band of sEMG signals could be considered for detecting muscle fatigue in various neuromuscular conditions.

Electromyography-based Fatigue Assessment During Endurance Testing by Different Vibration Training Protocols

Objectives: This study presents a method of assessing muscle fatigue during endurance testing at 50% maximal voluntary contraction (MVC) using electromyography (EMG) information as indirect indices of fatigability in the forearm muscles, namely, flexor digitorum superficialis (FDS); flexor carpi ulnaris (FCU); extensor carpi ulnaris (ECU) and extensor carpi radialis brevis (ECRB)." This study presents a method of assessing muscle fatigue during endurance testing at 50% maximal voluntary contraction (MVC) using electromyography (EMG) information as indirect indices of fatigability in the forearm muscles, namely, flexor digitorum superficialis (FDS); flexor carpi ulnaris (FCU); extensor carpi ulnaris (ECU) and extensor carpi radialis brevis (ECRB). Methods: A randomized comparative experimental design was used during endurance test with 8 VT protocols; based on different combinations of vibration frequency (35 &amp; 45 Hz), amplitude (3±0.5g &amp; 9±0.5g), and exposure duration (30 &amp; 60 seconds), i.e., were given to the study participants for 4 days. A random sampling of participants was conducted from two groups (n=56/group), as follows: individuals with a Sedentary Lifestyle (SL) and a group of Construction Workers (CW). Results: Multivariate Analysis of Variance (MANOVA) results indicated a significant increase in EMG rms, median frequency, waveform length, mean absolute value (P&lt;0.001), and the variance of EMG signal (P&lt;0.05) (except in ECU for the SL group and ECRB for the CW group on the variance of EMG signal) after VT in all muscles of both research groups. Therefore, an increase in the EMG parameter value after a grip endurance task revealing an elevation in EMG signal amplitude is indicative of muscle fiber fatigue. Furthermore, the strongest correlation was found between grip endurance and WL (r=0.471, P&lt;0.001), and EMG rms (r=0.401, P&lt;0.001) of the ECU muscle in the SL group only. Discussion: The patterns of EMG signal represented the amplitude and spectral parameters of the signal, enabling real-time fatigue analysis. Additionally, surface EMG information is useful for indirectly evaluating performance fatigue during the endurance test.

Assessment of muscle fatigue in perioral muscle after lip-closing training

Assessment of muscle fatigue in perioral muscle after lip-closing training

Electromyographic assessment of muscle fatigue after the Biering–Sorensen test in subjects with low back pain who underwent the McKenzie treatment

Chronic low back pain is a common disorder affecting about 80% of the population, caused by a disorder in the muscular system. The main aim of this study was to assess muscle fatigue during the Biering-Sorensen Test in people with chronic low back pain who underwent the McKenzie treatment. Tests were conducted on 19 men (mean age of 41.4 years) with chronic non-specific lumbar-sacral pain syndrome, working in the seated position in front of a computer. Assessment of changes in fatigue of erector spinae, gluteus maximus and biceps femoris using surface electromyography during the Biering-Sorensen Test and subjective pain assessment using Visual Analog Scale were conducted on three test dates. Time-frequency representation of the electromyographic signal (Fourier transform) was used for the examination of muscle fatigue. The McKenzie method of diagnosis and therapy was applied before and between the tests. The McKenzie therapy resulted in increased endurance (test duration) of the examined spinal muscles between the 1st and 3rd test date ( p = 0.043), and a systematic decrease in pain assessment on the three test dates ( p = 0.000-0.004). Correlations were obtained between slope coefficients of the simple regression of median frequency of electromyographic signals on the one hand and duration of the BST ( p = 0.000-0.012) and anthropometric parameters (body mass, height and body mass index, p = 0.001-0.020) on the other. The McKenzie method is an effective tool in reducing the level of lumbar pain and improving muscle endurance.