Muscle Fatigue Index Research Articles

Effects of Recreational Ski Mountaineering on Cumulative Muscle Fatigue - A Longitudinal Trial.

Sport is known to have many positive effects on mental and physical health. High-intensity exercise is considered to decrease muscle strength and induce muscle fatigue, which is associated with a higher risk of injury. In recreational alpine skiers, a decrease of eccentric peak hamstring torque, as an indication of muscle fatigue, occurs even after 1 day of skiing. The popularity of ski mountaineering is increasing enormously, but no studies are available on its effects on muscle strength. Therefore, the present study examined the consequences of ski mountaineering on muscle fatigue of the concentric/eccentric quadriceps and/or hamstrings. In addition, a possible role of myofascial foam rolling in reducing muscle fatigue was evaluated. Fifty recreational ski mountaineers (27 males, 23 females) completed five consecutive tours of ski mountaineering within 1 week. After each day of skiing, participants underwent an isokinetic muscle test assessing the concentric and eccentric muscle strength of both thighs. One group completed an additional session of myofascial foam rolling. Right and left concentric quadriceps peak torque, left hamstrings peak torque, left eccentric quadriceps peak torque, as well as right and left hamstring peak torque, were reduced after a single day of ski mountaineering (p ≤ 0.016 for all). However, no cumulative muscle fatigue was detected and we could not demonstrate any effect of myofascial foam rolling. The results show conclusively that a single day of ski mountaineering leads to a significant decrease of concentric and eccentric quadriceps and hamstring strength. Therefore, in order to improve muscle strength for the ski mountaineering season, a physical training program including concentric and eccentric methods can be recommended.

OR-028 Ageing effect of muscular athletic capability in knee joints over healthy woman aged 45 - 64 years

Objective It is important to evaluate the effect of age on muscular athletic capability in knee joints over healthy woman aged 45 to 64. The research could provide female ageing effect on muscular athletic capability for elderly persons, aiming to promote the relative research on exercise improvement and Women's health.
 Methods A total of 126 volunteers were selected. The knee muscle strength indexes were tested on side-to-side using self-developed digital isometric muscle function test system. Main indexes include muscle strength, muscle explosive force and muscle endurance on side-to-side. The age groups are classified with 5 years intervals recommended by WHO. The statistics of trend, correlation network, ANOVA and PCA were employed to distinguish the aging effects. All test were implemented in R platform (version 3.3.3).
 Results (1) muscle strength showed obvious differences between left and right; the relative higher explosive force occurred with extensor muscles on the left showing the significant changing point at 100 ms after 50; the muscle endurance and fatigue index showed side differences after 60. (2) muscle strength trend showed “down then up” characteristics with the slightly ahead of 55 on the right side as well as muscle endurance indexes. (3) indexes between explosive force variables showed strong significant difference (p<0.001) while muscle fatigue indexes showed side differences; muscle strength in flexor muscles displayed significant correlations with explosive force variables on the right but opposite in extensor muscles on the left. (4) the huge difference occurred in extensor groups especially the comparison between minimum and maximum groups. (5) the main influences on knee muscular athletic capability include explosive force variables as well as muscle fatigue index.
 Conclusions Both ageing effect and side effect are observed in muscular athletic capability in knee joints over healthy woman aged 45 - 64 years. After 55, the related variables showed decrease trend indicating the potential decreased muscular athletic capability. In both flexor and extensor muscles, strength variables displayed significant side differences, showing high explosive force in flexor muscles on the right side. The crucial age 50 and 55 became the turning points for knee muscular athletic capability especially with explosive forces.

Higher Training Frequency Is Important for Gaining Muscular Strength Under Volume-Matched Training.

Background: This study investigated the effect of volume-matched strength training programs with different frequency and subsequent detraining on muscle size and strength.Methods: During a training period of 11 weeks, untrained subjects (age: 22.3 ± 0.9 years, height: 173.1 ± 4.8 cm and body mass: 66.8 ± 8.4 kg) performed knee-extension exercise at 67% of their estimated one-repetition maximum either one session per week (T1 group: 6 sets of 12 repetitions per session; n = 10) or three sessions per week (T3 group: 2 sets of 12 repetitions per session; n = 10). Rating of perceived exertion (RPE) and muscle stiffness were measured as an index of muscle fatigue and muscle damage, respectively. The magnitude of muscle hypertrophy was assessed with thigh circumference and the quadriceps muscle thickness. The changes in muscle strength were measured with isometric maximum voluntary contraction torque (MVC).Results: During the training period, RPE was significantly higher in the T1 than in the T3 (p < 0.001). After 11 weeks of training, both groups exhibited significant improvements in thigh circumference, muscle thickness, and MVC compared with baseline values. However, there was a significant group difference in MVC improvement at week 11 (T1: 43.5 ± 15.5%, T3: 65.2 ± 23.2%, p < 0.05). After 6 weeks of detraining, both groups showed the significant decreases in thigh circumference and muscle thickness from those at the end of training period, while no significant effect of detraining was observed in MVC.Conclusion: These results suggest that three training sessions per week with two sets are recommended for untrained subjects to improve muscle strength while minimizing fatigue compared to one session per week with six sets.

The influence of job rotation and task order on muscle responses in females

Job rotation aims to reduce muscle fatigue by switching between functionally different tasks to theoretically lessen the risk of site-specific fatigue and work-related musculoskeletal disorders (WMSDs). The effectiveness of job rotation in mitigating the onset of muscle fatigue is partially known, but there is limited ergonomic data on female populations despite comparatively lower upper body strength and increased risk of WMSDs. Rotating between two functionally different tasks, continuing a single task, and varying task order were assessed in the present study for influence on muscle fatigue indicators in a female population. Participants performed a randomized set of four task combinations involving two unilateral, repetitive shoulder tasks (forward flexion and internal rotation). During these combinations, maximal voluntary force, mean power frequency, average EMG (aEMG) and ratings of perceived exertion (RPE) were recorded. Differences between task combinations and time were tested using a two-way repeated measures ANOVA. Indications of fatigue were limited in the results. Forward flexion (p = 0.004) and internal rotation (p = 0.002) maximum voluntary force declined in all task combinations while RPE increased (p < 0.0001); non-rotating task combinations had the greatest declines in force and increases in RPE. Results from EMG amplitude were less clear, and were muscle and task specific. While non-rotating task combinations had the greatest decrements in aEMG submaximal force, rotating task combinations often had similar decrements, creating limited statistical differences. Changes in aEMG were too small to distinguish an order effect. The EMG results suggest muscular demand overlap between the two tasks, despite being functionally different. The effectiveness of job rotation is partially dependent on selecting tasks that engage distinct muscle groups.

Comparative study on evaluation algorithms for neck muscle fatigue based on surface electromyography signal

The purpose of this study is to compare the differences among neck muscle fatigue evaluation algorithms and to find a more effective algorithm which can provide a human factor quantitative evaluation method for neck muscle fatigue during bending over the desk. We collected surface electromyography signal of sternocleidomastoid muscle of 15 subjects using wireless physiotherapy Bio-Radio when they bent over the desk using memory pillows for 12 minutes. Five algorithms including mean power frequency, spectral moments ratio, discrete wavelet transform, fuzzy approximation entropy and the complexity algorithms were used to calculate the corresponding muscle fatigue index. The least squares method was used to calculate the corresponding coefficient of determination R2 and slope k of the linear regression of the muscle fatigue metric. The coefficient of determination R2 evaluates anti-interference ability of algorithms. The maximum vertical distance Lmax which is obtained by the Kolmogorov-Smirnov test for the slopes k evaluates the ability to distinguish fatigue of algorithms. The results indicate that in the aspect of anti-interference ability, the fuzzy approximation entropy has the largest R2 when using memory pillows with different heights. When the fuzzy approximate entropy is compared with average power frequency or the discrete wavelet transform, the differences are significant ( P < 0.05). In terms of distinguishing the degree of fatigue, the approximate entropy is still the largest, with a maximum of 0.496 7. Fuzzy approximation entropy is superior to other algorithms in ability of anti-interference and distinguishing fatigue. Therefore, fuzzy approximation entropy can be used as a better evaluation algorithm in the evaluation of cervical muscle fatigue.

Wide-pulse, high-frequency, low-intensity neuromuscular electrical stimulation has potential for targeted strengthening of an intrinsic foot muscle: a feasibility study

BackgroundStrengthening the intrinsic foot muscles is a poorly understood and largely overlooked area. In this study, we explore the feasibility of strengthening m. abductor hallucis (AH) with a specific paradigm of neuromuscular electrical stimulation; one which is low-intensity in nature and designed to interleave physiologically-relevant low frequency stimulation with high-frequencies to enhance effective current delivery to spinal motoneurones, and enable a proportion of force produced by the target muscle to be generated from a central origin. We use standard neurophysiological measurements to evaluate the acute (~ 30 min) peripheral and central adaptations in healthy individuals.MethodsThe AH in the dominant foot of nine healthy participants was stimulated with 24 × 15 s trains of square wave (1 ms), constant current (150% of motor threshold), alternating (20 Hz–100 Hz) neuromuscular electrical stimulation interspersed with 45 s rest. Prior to the intervention, peripheral variables were evoked from the AH compound muscle action potential (Mwave) and corresponding twitch force in response to supramaximal (130%) medial plantar nerve stimulation. Central variables were evoked from the motor evoked potential (MEP) in response to suprathreshold (150%) transcranial magnetic stimulation of the motor cortex corresponding to the AH pathway. Follow-up testing occurred immediately, and 30 min after the intervention. In addition, the force-time-integrals (FTI) from the 1st and 24th WPHF trains were analysed as an index of muscle fatigue. All variables except FTI (T-test) were entered for statistical analysis using a single factor repeated measures ANOVA with alpha set at 0.05.ResultsFTI was significantly lower at the end of the electrical intervention compared to that evoked by the first train (p < 0.01). Only significant peripheral nervous system adaptations were observed, consistent with the onset of low-frequency fatigue in the muscle. In most of these variables, the effects persisted for 30 min after the intervention.ConclusionsAn acute session of wide-pulse, high-frequency, low-intensity electrical stimulation delivered directly to abductor hallucis in healthy feet induces muscle fatigue via adaptations at the peripheral level of the neuromuscular system. Our findings would appear to represent the first step in muscle adaptation to training; therefore, there is potential for using WPHF for intrinsic foot muscle strengthening.

The Evaluation of Shoulder Muscle Fatigue in Volleyball Players

Objective: To identify the difference in infraspinatus, posterior deltoid, and teres minor muscle fatigability between the dominant and non-dominant side in elite volleyball players and to examine the differences between three sEMG signal processing methods used in assessment of shoulder muscle imbalance due to fatigue in volleyball players. Methods: In 18 male volleyball players (21-26 years; 186.6 ± 8.4 cm; 85.7 ± 9.8 kg) with no previous shoulder injury the bioelectrical activity of the right and left infraspinatus, posterior deltoid, and teres minor muscles was measured during 60 seconds of isometric contraction in prone position with the shoulder in external rotation. Fatigue related changes as mean frequency shift were calculated from the RAW sEMG signal using 3 processing methods: FFT (Fast Fourier Transform), STFT (Short Time Fourier Transform) and CWT (Morlet Continues Wavelet Transform). Results: There were no statistically significant differences (p>0.05) in the values of the mean frequency slope, intercept and difference between dominant and non-dominant sides in all the evaluated muscles. There were no significant differences between FFT and STFT sEMG signal processing methods in mean frequency slope, intercept values and difference. The sEMG signal processing using CWT showed the significantly higher values of mean frequency slope for infraspinatus and teres minor muscles. Significantly lower values of mean frequency intercept were observed for the infraspinatus, posterior deltoid and the teres minor muscles. There were no significant differences observed in mean frequency difference for all the evaluated muscles. Conclusions: In elite volleyball players without previous shoulder injury, the fatigue indices in muscles of the shoulder region were similar on both the dominant and non-dominant sides. Therefore, we have hypothesized that asymmetric shoulder loading during volleyball training should not be considered as an obvious factor increasing the risk of shoulder injury. Muscle fatigue indices measured by sEMG may be a sensitive and objective method of evaluation, but may reach different values depending on the used signal processing method. Consequently, the clinical interpretation and any comparison between different measurements, without knowledge of how those values were calculated, may be misleading and be the reason for misdiagnosis.

PERBEDAAN EFEKTIVITAS PEMBERIAN PISANG RAJA DAN PISANG AMBON TERHADAP INDEKS KELELAHAN OTOT ANAEROBIK PADA REMAJA DI SEKOLAH SEPAK BOLA

Background : Anaerobic muscle fatigue occurs due to accumulation of lactic acid, causing soreness and reduced muscle contraction. Raja banana (Musa paradisiaca var. Sapientum L.) and Ambon banana (Musa paradisiaca var. Sapientum (L.) Kunt.) are high in carbohydrate and potassium which are involved in increasing blood glucose, thus consuming bananas before exercising may help prevent muscle fatigue.This study aimed to determine the effectiveness of Raja and Ambon bananas on anaerobic. muscle fatigue index of adolescents in football school.Methods :This study was a quasi-experimentusingthe posttest-only with control group design.Thirty-nine male adolescents aged 15-18 years at Terang Bangsa and Satria Kencana Serasi football schools were recruited and classified into 3 groups: control (240 ml of mineral water), group I (150 g Raja banana fruit), and group II (150 g of Ambon banana fruit). Anaerobic muscle fatigue was measured by Running-base Anaerobic Sprint Test (RAST) to calculate Anaerobic Fatigue (AF) value. Data were analyzed by One way ANOVA and ANCOVA test.Results :The average AF index in control group (11.53±2.20) was significantly different with group I (4.30±0.80; p=0.001), and group I with group II (9.76 ± 2.34; p=0,001). However not significantly different between the averageAF Index of control group withgroup II.Conclusion :There is a significant difference in the effectiveness of Raja and Ambon banana on reducing anaerobic muscle fatigue for adolescents in football school. Raja banana demonstratedbetter effects on muscle fatiguein comparison withAmbon banana.

Muscle fatigue indicators during paced live-fire shooting with and without a body armor-integrated prototype weapon mount

Introduction: Small arms weapon systems are vital to a soldier's operational effectiveness and survivability. Soldiers are fielded with a variety of different weapon systems. The mass and weight distribution of these weapons can vary greatly due to design, ammunition type, and sighting systems. An articulated prototype weapon mount (3ARM) was developed that integrates with soldier body armor to help support the load of the weapon and provide stability for weapon aim. A pilot evaluation was conducted to quantify muscle contraction and muscular fatigue during paced live-fire shooting with and without the 3ARM.

Continuous Wavelet Transform Analysis of Surface Electromyography for Muscle Fatigue Assessment on the Elbow Joint Motion

Studying muscle fatigue plays an important role in preventing the risks associated with musculoskeletal disorders. The effect of elbow-joint angle on time-frequency parameters during a repetitive motion provides valuable information in finding the most accurate position of the angle causing muscle fatigue. Therefore, the purpose of this study is to analyze the effect of muscle fatigue on the spectral and time-frequency domain parameters derived from electromyography (EMG) signals using the Continuous Wavelet Transform (CWT). Four male participants were recruited to perform a repetitive motion (flexion and extension movements) from a non-fatigue to fatigue condition. EMG signals were recorded from the biceps muscle. The recorded EMG signals were then analyzed offline using the complex Morlet wavelet. The time-frequency domain data were analyzed using the time-averaged wavelet spectrum (TAWS) and the Scale-Average Wavelet Power (SAWP) parameters. The spectral domain data were analyzed using the Instantaneous Mean Frequency (IMNF) and the Instantaneous Mean Power Spectrum (IMNP) parameters. The index of muscle fatigue was observed by calculating the increase of the IMNP and the decrease of the IMNF parameters. After performing a repetitive motion from non-fatigue to fatigue condition, the average of the IMNF value decreased by 15.69% and the average of the IMNP values increased by 84%, respectively. This study suggests that the reliable frequency band to detect muscle fatigue is 31.10-36.19Hz with linear regression parameters of 0.979mV^2Hz^(-1) and 0.0095mV^2Hz^(-1) for R^2 and slope, respectively.

Volume Load and Neuromuscular Fatigue During an Acute Bout of Agonist-Antagonist Paired-Set vs. Traditional-Set Training.

The purpose of this study was to investigate the acute effects of performing paired-set (PS) vs. traditional-set (TS) training over 3 consecutive sets, on volume load and electromyographic fatigue parameters of the latissimus dorsi, biceps brachii, pectoralis major, and triceps brachii muscles. Fifteen trained men performed 2 testing protocols (TS and PS) using 10 repetition maximum loads. The TS protocol consisted of 3 sets of bench press (BP) followed by 3 sets of wide-grip seated row (SR). The PS consisted of 3 sets of BP and 3 sets of SR performed in an alternating manner. Volume load was calculated as load × repetitions. The electromyographic signal, time (CRMS) and frequency (Cf5) domain, parameters were recorded during SR. Under the PS protocol, sets of SR were performed immediately after the sets of BP. A 2-minute rest interval between the completion of the set of SR and the subsequent set of BP was implemented (e.g., between PSs). Under the TS protocol, 2-minute rest intervals were implemented between all sets. BP and SR volume loads decreased significantly from set 1 to set 2 and from set 2 to set 3 under both conditions. Volume load was greater for all sets of both exercises under PS as compared with TS. Muscle fatigue indices were greater under PS as compared with TS. In general, these results indicate that as compared with TS, PS produced a greater training volume in less time and may induce greater fatigue and thereby provide an enhanced training stimulus.

Myoelectric manifestation of muscle fatigue in repetitive work detected by means of miniaturized sEMG sensors

Upper limb work-related musculoskeletal disorders have a 12-month prevalence ranging from 12 to 41% worldwide and can be partly caused by handling low loads at high frequency. The association between the myoelectric manifestation of elbow flexor muscle fatigue and occupational physical demand has never been investigated. It was hypothesized that an elbow flexor muscle fatigue index could be a valid risk indicator in handling low loads at high frequency. This study aims to measure the myoelectric manifestation of muscle fatigue of the three elbow flexor muscles during the execution of the work tasks in different risk conditions. Fifteen right-handed healthy adults were screened using a movement analysis laboratory consisting of optoelectronic, dynamometer and surface electromyographic systems. The main result indicates that the fatigue index calculated from the brachioradialis is sensitive to the interaction among risk classes, session and gender, and above all it is sensitive to the risk classes.

Mechanomyography-Based Wearable Monitor of Quasi-Isometric Muscle Fatigue for Motor Neural Prostheses.

A motor neural prosthesis based on surface functional electrical stimulation (sFES) can restore functional movement (e.g., standing, walking) in patients with a spinal cord injury (SCI). sFES generates muscle contractions in antigravity muscles and allows balance-assisted standing. This induced standing has several benefits, such as improved cardiovascular function, decreased incidence of urinary infections, reduced joint contractures, and muscle atrophy. The duration of sFES assisted standing is limited due to the quick onset of muscle fatigue. Currently, there is no method available to reliably estimate real-time muscle fatigue during sFES. Simply monitoring the M-wave changes is not suitable due to the high signal disturbances that arise during multi-channel electrical stimulation. Mechanomyography (MMG) is immune to electrical stimulation artifacts and can be used to detect subtle vibrations on the surface of the skin related to activation of the underlying muscle's motor units (MU). The aim of this study was to develop a method for detecting muscle fatigue brought on by sFES. The method was tested in three different heads of the quadriceps muscle in SCI patients during electrically elicited quasi-isometric contraction. Six spinal cord-injured male volunteers, with no voluntary control of the quadriceps muscle participated in the study. Electrical bursts of voltage-controlled monophasic square pulses at frequencies of 1 kHz (50% duty cycle) at 50 Hz (15% duty cycle) were used to generate thigh muscle contractions that controlled the knee joint in the sagittal plane. The pulse amplitudes were set to position the knee joint at a 5° angle from the horizontal plane and when the knee angle dropped to 20° (e.g., the quadriceps were unable to hold the lower leg in the desired position), the test was terminated. Two data segments lasting 10 s each, at the beginning and end of each test, were analyzed. The muscle contraction was assessed by MMG sensors positioned on the rectus femoris, vastus lateralis, and vastus medialis muscles. Data segments were decomposed into 11 frequency bands using a Cauchy wavelet transform. In the initial time interval (non-fatigued muscle), the power peak was concentrated in the 11.31 Hz frequency band. In the final interval (muscle fatigued) this peak shifted to lower frequencies (2 and 6 Hz frequency bands). The decreased frequency was most prominent during the last 4 s of the recordings. It was shown that MMG could be used as a real-time indicator of muscle fatigue during FES-induced isometric contraction of quadriceps; hence, MMG could be used in closed-loop control as a fatigue detector. Subsequent studies for non-isometric contractions could possibly lead to prediction of muscle fatigue before contractile failure during functional use of the muscle.

Assessment of tongue mechanical properties using different contraction tasks.

Inadequate upper airway (UA) dilator muscle function may play an important role in the pathophysiology of obstructive sleep apnea (OSA). To date, tongue mechanical properties have been assessed mainly using protrusion protocol with conflicting results. Performance during elevation tasks among patients with OSA remains unknown. This study aimed at assessing tongue muscle strength, strength stability, endurance time, fatigue indices, and total muscle work, using elevation and protrusion tasks with repetitive isometric fatiguing contractions in 12 normal plus mild, 17 moderate, and 11 severe patients with OSA, and to assess the influence of body mass index (BMI) and age. Endurance time was longer in protrusion than elevation task (P = 0.01). In both tasks, endurance time was negatively correlated with baseline value of strength coefficient of variation (P < 0.01). Compared with other groups, patients with moderate OSA had the lowest total muscle work for protrusion (P = 0.01) and shortest endurance time (P = 0.04), regardless of the type of task. Additionally, in patients with moderate-severe OSA, the total muscle work for both tasks was lower in nonobese compared with obese (P < 0.05). Total muscle work for protrusion was positively correlated with apnea hypopnea index (AHI) in obese subjects (P < 0.01). Endurance time was shorter (P < 0.01) and recovery time longer (P = 0.02) in the old compared with young subjects. In conclusion, the tongue is more prone to fatigue during the elevation task and in patients with moderate OSA. Obesity appeared to prevent alteration of tongue mechanical properties in patients with OSA. Baseline strength stability and endurance were related, illustrating the role of central neuromuscular output in tongue resistance to fatigue.NEW & NOTEWORTHY To our knowledge, this is the first study to assess and compare tongue function using both elevation and protrusion tasks with repetitive isometric fatiguing contractions in subjects with different OSA status. Tongue mechanical performance seemed to differ between protrusion and elevation tasks and depend on the severity of OSA.

Influence of gender on muscle fatigue during dynamic knee contractions.

The purpose was to compare quadriceps muscle fatigue and change in surface electromyogram (sEMG) spectral power, muscle thickness, and peak torque (normalized by body weight) in men and women during isokinetic knee contractions. Nineteen healthy volunteers (10 men, 9 women) participated. The volunteers performed 32 consecutive maximal isokinetic knee contractions for peak torque and muscle fatigue index (FI). The sEMG data were analyzed using wavelet analysis for median frequency (MF). Muscle thickness was measured using ultrasonography. Men had a significantly higher FI, peak torque (Nm/kg), muscle thickness than women (p<0.05). A significant linear decreased MF slope in the vastus lateralis was observed (p<0.05) in men than in women. There was no significant difference in MF slope in the vastus medialis between men and women. During muscle fatigue assessment, men had a significantly greater muscle thickness, knee extension peak torque, and a higher decrease of MF slope than women. Our results indicate that specific muscle fatigue observed during repeated muscle knee contractions is significantly influence by gender and affects MF slope, knee extension peak torque, and muscle thickness.

The Effect of Abdominal Drawing-in Maneuver for the Wellness of Patients with Chronic Neck Pain - Focused on Neck Muscle Fatigue and Neck Disability Index -

The Effect of Abdominal Drawing-in Maneuver for the Wellness of Patients with Chronic Neck Pain - Focused on Neck Muscle Fatigue and Neck Disability Index -

Neuromuscular control strategies of the trunk antagonist muscles during the Biering-Sorensen test in individuals with recurrent low back pain and healthy subjects

OBJECTIVES To compare the activation pattern of the trunk antagonistic muscles and also the myoelectric manifestations of muscle fatigue between subjects with and without recurrent non-specific low back pain, during the fatigue provocation of the erector spinae. METHODS The study involved 19 subjects with recurrent low back pain with a non-specific cause (seven men, 12 women, 38.53 ± 8.12 years, 68.35 ± 18.12 kg, 1.66 ± 0.09 m), and 19 healthy subjects (seven men, 12 women, 40.42 ± 8.63 years, 69.57 ± 12.76 kg, 1.64 ± 0.07 m). The electromyographic signal of the internal oblique, lumbar multifidus, rectus abdominis and lumbar iliocostalis muscles, bilateral, were collected during Biering-Sorensen test execution. RESULTS The group with low back pain showed a lower co-contraction rate of the internal oblique/lumbar multifidus (p = 0.006) and lower activation amplitude of the internal oblique (p = 0.019), both on the right side when compared to the group without low back pain. No differences were observed between the groups for muscle fatigue indicators (p > 0.05). CONCLUSION When the erector spine muscle fatigue occurs - even when the groups were similar as to the ability of extensors muscles to resist fatigue - differences were found between subjects with and without low back pain regarding the recruitment pattern of the task antagonist muscle, because subjects with low back pain showed lesser activation and co-contraction in relation to the healthy group.

Surface EMG Based Muscle Fatigue Evaluation on Neck-Shoulder Muscles while Using Single-Monitor Arm

The median frequency (MF) and mean power frequency (MPF) have been confirmed as reliable indicators of muscle fatigue during sustained contractions. The purpose of this study was to explore whether single-monitor arm could release muscle fatigue in neck-shoulder region while maintaining a prolonged seated posture viewing computer screen by measuring MF and MPF. Ten male healthy university students volunteered to participate in the test. Surface electromyography of splenius capitis (SC) and trapezius (TR) were recorded. Each subject performed normal text editing tasks or video watching activities for 120 minutes with different monitor arm positions (Fixed, moving downward and moving upward). Results showed that the MPF of SC and TR had significant decreased trend as monitor arm at fixed position. As monitor arm moving upward, the MF and MPF of both muscles decreased significantly with time and the MF showed the lowest decline rate during the entire testing process. No significant shift of MF and MPF were observed as monitor arm moving downward. Findings of this study may have important implications for people who use computer intensively to release neck-shoulder muscle fatigue.

Estimation of muscle fatigue by ratio of mean frequency to average rectified value from surface electromyography.

A new method to estimate muscle fatigue quantitatively from surface electromyography (EMG) is proposed. The ratio of mean frequency (MNF) to average rectified value (ARV) is used as the index of muscle fatigue, and muscle fatigue is detected when MNF/ARV falls below a pre-determined or pre-calculated baseline. MNF/ARV gives larger distinction between fatigued muscle and non-fatigued muscle. Experiment results show the effectiveness of our method in estimating muscle fatigue more correctly compared to conventional methods. An early evaluation based on the initial value of MNF/ARV and the subjective time when the subjects start feeling the fatigue also indicates the possibility of calculating baseline from the initial value of MNF/ARV.

Comparison of mean frequency and median frequency in evaluating muscle fiber type selection in varying gait speed across healthy young adult individuals.

The preferential slow and fast twitches fiber involvement in varying gait speed has not been thoroughly investigated. Attempt to classify fiber type in changing speed should be closely investigated and scrutinized as the histochemical-related experiments are cumbersome and time consuming. In addressing this issue, electromyography (EMG) is utilized to extract the muscle fiber type features by altering the muscle fatigue indices, namely mean frequency (MNF) and median frequency (MDF). Recently, there are no universal indices to determine the muscle type. In this paper, the MNF and MDF are employed in discovering the muscle type variation as the speed changes. Besides drawing the potential of MNF and MDF in unveiling the muscle type, both the parameters are applied to investigate the muscles that are recruited and which muscle type are involved as the gait velocity changes. In this study, six healthy and young participants are recruited, whereby the EMG sensors are placed on twelve lower extremity muscles. The EMG signals are then processed via Matlab software to deduce MNF and MDF. The MNF and MDF are determined from every of the phase gait, namely stance and swing. From the results obtained, it reveals that the superiority of the MNF over the MDF in determining and interpreting the muscle recruitment in both gait phases as the speed increases. The MNF, moreover, is able to show an apparent difference in muscle type selection compared to MDF. Interestingly, it is discovered that as the speed increases from slow to fast, the MNF decreases, which indicates that more muscle fiber type I is recruited. Contrarily, the MNF increases as the speed intensity decreases, which indicates that the distribution of muscle type II is prominent.