sEMG Variables Research Articles

Coordination strategies of lower limb muscles during curve-turning tasks in preschool children

BackgroundPreschoolers are within their critical time in motion development; while muscles are the fundamental units in motion control and by monitoring activated intensity and duration of muscles, preschooler’s motor ability which would disclose their potential pathogenesis quality can be objectively and quantitatively assessed. Although a large number of studies were available on this issue, questions still being there: what are the patterns and characteristics of lower limb muscles when they are facing with the curve walking(CW) tasks; and then how individual muscle or muscle groups coordinated while turning curves. Our purpose of this study is first to portray the patterns and characteristics of lower limb muscles of healthy preschoolers while CW and then to insight their muscles’ coordination mechanism and "neuro-musculo-skeletal" feedback during motion. Method35 healthy preschoolers and 35 healthy adults’ lower limbs surface electromyography (sEMG) were collected while left and right CW and four muscle groups (Tibialis Anterior, Lateral Gastrocnemius, Rectus Femoris, and Biceps Femoris) were recorded. sEMG variables such as Muscle Activation Time, Total Duration of Activity Time, Average Muscle Activation Rate and Average Rate of Change were calculated. Paired sample t-test was used to explore the differences of sEMG variables between preschoolers and adults when turning curves. ResultsPreschoolers would adjust the gait by changing the activation time and activation rate to fulfill the curve turning tasks; but they also showed variations in coordination mechanism when contrasting with the adults group. Those findings in preschoolers would support to build muscles’ coordination mechanism and further insight to neuro-muscular skeletal feedback regulation. ConclusionAlthough preschoolers performed good enough to switching gait from normal walking to CW, but gaps in their abilities were still apparent when compared to adults. Hence, with the help of highly recognizable muscle coordination mechanism in CW, motor dysfunction in lower limbs of preschool children can be effectively identified.

Lower-limbs’ muscle coordination mechanism of healthy preschoolers while walking across obstacles

Research backgroundThe obstacle-crossing task is a complex gait task, it requires an advance predict of the obstacle for posture adjustment and accurate control of bilateral legs to ensure crossing the obstacles successfully. By monitoring the activated intensity and duration of muscles in this process, preschoolers' motor ability could be assessed objectively and quantitatively, as well as disclose their potential pathogenesis quality eventually. Scientific questionwhat are the patterns and characteristics of lower limb muscles when they are facing the obstacle-crossing walking (OW) tasks, and how they coordinate their individual muscle or muscle groups of lower-limbs muscles while walking across obstacles? Thereby, the purpose of this study was first to portray the patterns and characteristics of lower limb muscles of healthy preschoolers while OW motion and second to assess the muscles’ coordination mechanism. Method35 healthy preschoolers and 35 healthy adults’ lower limbs' surface electromyography (sEMG) were collected while left and right OW and four muscle groups (Tibialis Anterior, Lateral Gastrocnemius, Rectus Femoris, and Biceps Femoris) were recorded. sEMG variables such as Muscle Activation Time, Total Duration of Activity Time, Average Muscle Activation Rate, and Average Rate of Change were calculated. The paired sample-t-test was used to explore the differences of sEMG variables between preschoolers and adults when obstacle-crossing. ResultsPreschoolers would adjust the gait by changing the activation time and activation rate to fulfill the obstacle crossing tasks, but they also showed variations by contrasting to adults. Further, synergy between muscles in leg and thigh were also found. ConclusionAlthough preschoolers performed well enough to finish the OW tasks, ability gaps were still apparent when compared to adults. Hence, with the help of a deeply recognizable muscle coordination mechanism in OW, motor dysfunction in the lower limbs of preschool children can be effectively identified.

Bench, Bar, and Ring Dips: Do Kinematics and Muscle Activity Differ?

The purpose of this study was to profile and compare the kinematics, using 3D motion capture, and muscle activation patterns, using surface electromyography (sEMG), of three common dip variations; the bench, bar, and ring dips. Thirteen experienced males performed four repetitions of each dip variation. For each participant, repetitions 2–4 were time-normalized and then averaged to produce a mean value for all kinematic and sEMG variables. The mean maximal joint angles and mean peak sEMG amplitudes were compared between each variation using a one-way ANOVA with repeated measures. Several significant differences (p < 0.05) between dip variations were observed in both kinematic and sEMG data. The bench dip predominantly targets the triceps brachii but requires greater shoulder extension range. The mean peak triceps brachii activation was 0.83 ± 0.34 mV on the bench, 1.04 ± 0.27 mV on the bar, and 1.05 ± 0.40 mV on the ring. The bar dip is an appropriate progression from the bench dip due to the higher peak muscle activations. The ring dip had similar peak activations to the bar dip, with three muscles increasing their activation intensities further. These findings have implications for practitioners prescribing the dip, particularly to exercisers with a history of shoulder pain and injury.

Interaction between age and fatigue on antagonist muscle coactivation during an acute post-fatigue recovery phase.

This study investigated the age-related changes in antagonist muscle coactivation of the biceps femoris (BF) during an acute recovery period following a leg extensor fatiguing protocol. Twenty-three young (mean ± SD: age = 25.1 ± 3.0 years) and twenty-three old men (age = 71.5 ± 3.9 years) participated. Surface electromyography (sEMG) was recorded from the BF muscles for antagonist muscle coactivation. Testing involved participants performing leg extension isometric maximal voluntary contractions (MVCs) and isokinetic MVCs at 240°·s−1 at baseline (Pre) and again after the fatigue protocol at 0 (Post0), 7 (Post7), 15 (Post15), and 30 (Post30) minutes post fatigue. Root mean square (RMS) values were computed from the BF sEMG and were calculated as the first 200 ms from onset for the isometric (IsomCoact200ms) and dynamic isokinetic 240°·s−1 (DynCoact200ms) MVCs, and for the final 10° of the leg extension (DynCoact10°) on the isokinetic 240°·s−1 MVCs. Two-way ANOVAs [age group (young vs. old) × time (Pre vs. Post0 vs. Post7 vs. Post15 vs. Post30)] showed that DynCoact200ms had an effect for time (p = 0.018), with greater antagonist coactivation in Pre than Post0 (p = 0.009) and recovering by Post7 (p = 0.011) with no group differences. DynCoact10° had no age × time interaction (p = 0.070), but had a main effect for time (p = 0.020) with the Post0 being lower than the Pre. However, for this variable the young group showed a more severe Pre to Post0 fatigue decline (−45.9%) than the old group (−6.7%) indicating this may be a more sensitive variable for capturing age-related antagonist coactivation post-fatigue responses. Leg extensor fatigue affects some BF coactivation sEMG variables more than others, and any altered post-fatigue coactivation response recovers rapidly (<7 min) from baseline levels.

Predictors of Step Length from Surface Electromyography and Body Impedance Analysis Parameters.

Step length is a critical hallmark of health status. However, few studies have investigated the modifiable factors that may affect step length. An exploratory, cross-sectional study was performed to evaluate the surface electromyography (sEMG) and body impedance analysis (BIA) parameters, combined with individual demographic data, to predict the individual step length using the GAITRite® system. Healthy participants aged 40–80 years were prospectively recruited, and three models were built to predict individual step length. The first model was the best-fit model (R2 = 0.244, p < 0.001); the root mean square (RMS) values at maximal knee flexion and height were included as significant variables. The second model used all candidate variables, except sEMG variables, and revealed that age, height, and body fat mass (BFM) were significant variables for predicting the average step length (R2 = 0.198, p < 0.001). The third model, which was used to predict step length without sEMG and BIA, showed that only age and height remained significant (R2 = 0.158, p < 0.001). This study revealed that the RMS value at maximal strength knee flexion, height, age, and BFM are important predictors for individual step length, and possibly suggesting that strengthening knee flexor function and reducing BFM may help improve step length.

The role of age on neuromuscular performance decay induced by a maximal intensity sprint session in a group of competitive endurance athletes.

Age-related changes in the neuromuscular system functions may affect profoundly high-level athletes' performance across their careers. The present study aimed to analyse the fatiguing effect of a maximal intensity sprint session (MISS) on competitive athletes of different ages. Thirty-one competitive endurance athletes completed a knee extensors and flexors' maximal-voluntary-isometric-contraction (MVC) test before and after a maximal-intensity-sprint-session (MISS) consisting of 4x15s Wingate-tests. The data have been stratified considering three age categories (18-28, n=11, 29-38; n=10; 39-43, n=10). Overall, both quadricep and hamstring muscles early and late rate of torque development (RTD) dropped significantly more than the maximal voluntary torque (MVT) (p<.05). Age had a significant effect on early RTD, with older athletes exhibiting greater RTD (p<.05). A significant effect of age also emerged for the changes in surface sEMG variables, in which the frequency spectrum variables dropped significantly more than the sEMG amplitude (RMS) (p<.05). The dynamics of changes in neuromuscular performance markers after a MISS suggested that getting older competitive athletes may potentially experience a greater loss in early explosive strength compared to maximal or late explosive strength.

Retentive capacity of power output and linear versus non-linear mapping of power loss in the isotonic muscular endurance test

The limit of dynamic endurance during repetitive contractions has been referred to as the point of muscle fatigue, which can be measured by mechanical and electrophysiological parameters combined with subjective estimates of load tolerance for revealing the human real-world capacity required to work continuously. In this study, an isotonic muscular endurance (IME) testing protocol under a psychophysiological fatigue criterion was developed for measuring the retentive capacity of the power output of lower limb muscles. Additionally, to guide the development of electrophysiological evaluation methods, linear and non-linear techniques for creating surface electromyography (sEMG) models were compared in terms of their ability to estimate muscle fatigue. Forty healthy college-aged males performed three trials of an isometric peak torque test and one trial of an IME test for the plantar flexors and knee and hip extensors. Meanwhile, sEMG activity was recorded from the medial gastrocnemius, lateral gastrocnemius, vastus medialis, rectus femoris, vastus lateralis, gluteus maximus, and biceps femoris of the right leg muscles. Linear techniques (amplitude-based parameters, spectral parameters, and instantaneous frequency parameters) and non-linear techniques (a multi-layer perception neural network) were used to predict the time-dependent power output during dynamic contractions. Two mechanical manifestations of muscle fatigue were observed in the IME tests, including power output reduction between the beginning and end of the test and time-dependent progressive power loss. Compared with linear mapping (linear regression) alone or a combination of sEMG variables, non-linear mapping of power loss during dynamic contractions showed significantly higher signal-to-noise ratios and correlation coefficients between the actual and estimated power output. Muscular endurance required in real-world activities can be measured by considering the amount of work produced or the activity duration via the recommended IME testing protocol under a psychophysiological termination criterion. Non-linear mapping techniques provide more powerful mapping of power loss compared with linear mapping in the IME testing protocol.

Surface electromyography of the pelvic floor at 6-8 weeks following delivery: a comparison of different modes of delivery.

The objective of this study was to compare the impact of different modes of delivery, especially forceps delivery (FD), on pelvic floor muscles (PFMs) through vaginal surface electromyography (sEMG) in primiparous women at early (6-8weeks) postpartum. A total of 1259 primiparous women with full-term singleton births were included in this cross-sectional study. Of these, 98 were delivered by forceps, 865 underwent spontaneous vaginal delivery (SD) and 296 underwent elective cesarean delivery (CD). Clinical demographic characteristics and vaginal sEMG variables of parturients 6-8weeks after birth were collected and analyzed using SPSS software. One-way ANOVA with Bonferroni correction, Chi-square test or Student's t-test was used according to the variable type. Spearman correlation and binary logistic regression analyses were also used. P/α ≤ 0.05 was considered statistically significant. Amplitude of fast and sustained contractions on sEMG in the FD group was significantly lower compared with the CD and SD groups. The sEMG amplitude of all contractions was significantly higher in the CD group compared with the FD and SD groups (P < 0.01). According to binary logistic regression analysis, mode of delivery was a major influencing factor in sEMG. An early postpartum sEMG test appears to be helpful for the assessment of PFM activity. Mode of delivery was a major influencing factor on sEMG. Forceps delivery significantly inversely influenced PFM activity.

Is fatigue a muscular phenomenon in Parkinson's disease? Implications for rehabilitation.

Fatigue in Parkinson's disease (PD) compromises patients' physical activity and poses questions on how to plan correct rehabilitation training. In addition, the relationship between subjective perceived fatigue and fatigue in motor performance is not yet entirely understood. Therefore, a conclusive interpretation of muscular mechanisms of fatigue in PD has not yet been achieved. Among the various instrumental evaluations for fatigue, multichannel surface electromyography (sEMG) is a recognized tool that permits the study of myoelectric manifestations of fatigue. The aim of this study was to assess if muscles in PD show a different myoelectric fatigue pattern compared to the muscles of healthy age-matched subjects. The design was observational controlled study. Idiopathic Parkinson's Disease, Hohen &Yahr II and III stage, Parkinsonian Fatigue Scale average score ≥2.95, no therapy modification in the 4 weeks preceding the study; exclusion criteria: mini mental state examination ≤24, upper limb disease/symptoms that might interfere with sEMG analysis, presence of other fatigue-related conditions. Twenty patients were selected according to these criteria. Twenty untrained healthy subjects were matched. All subjects underwent a muscle fatigue protocol and a sEMG analysis of the right biceps brachii muscle during electrically stimulated and voluntary contractions in order to obtain a myoelectric fatigue muscular pattern. The myoelectric pattern is characterized by the modifications of the following sEMG variables: reduction of mean frequency and muscle fiber conduction velocity, increase of average rectified value. No statistical differences were observed between groups for sEMG variables and muscular electric behavior in all contraction conditions (all P>0.05). Our results show that parkinsonian muscles do not differ from the muscles of healthy age-matched subjects in developing peripheral myoelectric fatigue. Nevertheless, the role of fatigue perception at rest and particularly during physical activity must be clearly understood in order to further target the rehabilitative approach for fatigued parkinsonian patients and to reduce hypomobility. In rehabilitative terms, these findings allow us to highlight the possibility of performing sustained training with isometric contractions in PD subjects; therefore, fatigue "per se" does not constitute a barrier for the execution of muscular exercises, likewise intensive.

Intra-Day and Inter-Day Reliability of Measurements of the electromyographic signal on masseter and temporal muscles in patients with Down syndrome

The aim of the present study was to evaluate intra-day (test) and inter-day (re-test) reliability of surface electromyography (sEMG) signals of the masseter and temporal muscles in patients with Down syndrome (DS). We determined the reliability of sEMG variables in 33 patients with DS. EMG signals were recorded at rest as well as during maximum voluntary clenching and maximum habitual intercuspation (MHI). The signals were analyzed considering the amplitude in the root mean square (RMS), mean frequency (MNF), median frequency (MDF) and approximate entropy (ApEn). The intraclass correlation (ICC2,1) for the three trials recorded during MHI in the two sessions (test and retest) revealed excellent intra-session and inter-session reliability (ICC2,1 = 0.76 to 0.97) for all sEMG variables and muscles. In the rest position, excellent reliability was found for RMS and ApEn (ICC2,1 = 0.75 to 1.00) and good to excellent reliability was found for MDF and MNF (ICC2,1 = 0.64 to 0.93). The intra-session (test) and inter-session (re-test) analyses demonstrated the reliability of nonlinear sEMG variables of the masticatory muscles in adults with Down Syndrome.

Muscle Activation and Driving Performance Differences Between Static and Dynamic Driving Simulation Conditions

The purpose of this work was to compare simulator and surface electromyography (sEMG) variables between fixed base (FBDS) and dynamic driving (DDS) simulation conditions using a hexapod robot based driving simulator during 90 degree turning manoeuvers. Nine males and nine females, who wore a light-weight head mounted display to provide the visual input, drove faster in the DDS leading to faster turn exit velocities and turn completion times. For sEMG variables, one of the most common findings was that when making left turns, higher muscle activity was observed in the DDS. This suggests that DDS driving does differ from FBDS driving. Information provided by this work shows that simulator movement affects muscle activation, therefore, care should be taken when interpreting results from FBDS to not assume that similar results would be found in DDS, and by extension naturalistic driving.

Full gait cycle analysis of lower limb and trunk kinematics and muscle activations during walking in participants with and without ankle instability

BackgroundChronic ankle instability (CAI) has previously been linked to altered lower limb kinematics and muscle activation characteristics during walking, though little research has been performed analysing the full time-series across the stance and swing phases of gait. Research QuestionThe aim of this study was to compare trunk and lower limb kinematics and muscle activity between those with chronic ankle instability and healthy controls. MethodsKinematics and muscle activity were measured in 18 (14 males, 4 females) healthy controls (age 22.4 ± 3.6 years, height 177.8 ± 7.6 cm, mass 70.4 ± 11.9 kg, UK shoe size 8.4 ± 1.6), and 18 (13 males, 5 females) participants with chronic ankle instability (age 22.0 ± 2.7 years, height 176.8 ± 7.9 cm, mass 74.1 ± 9.6 kg, UK shoe size 8.1 ± 1.9) during barefoot walking trials, using a combined Helen Hayes and Oxford foot model. Surface electromyography (sEMG) was recorded for the tibialis anterior and gluteus medius. Full curve statistical parametric mapping was performed using independent and paired-samples T-tests. ResultsNo significant differences were observed in kinematic or sEMG variables between or within groups for the duration of the swing phase of gait. A significantly increased forefoot-tibia inversion was seen in the CAI affected limb when compared to the CAI unaffected limb at 4–16% stance (p = 0.039). No other significant differences were observed. SignificanceThere appears to be no differences in muscle activation and movement between CAI and healthy control groups. However, participants with CAI exhibited increased inversion patterns during the stance phase of gait in their affected limb compared to their unaffected limb. This may predispose those with CAI to episodes of giving way and further ankle sprains.

Reduced complexity of force and muscle activity during low level isometric contractions of the ankle in diabetic individuals

BackgroundThis study evaluated the structure and amount of variability of surface electromyography (sEMG) patterns and ankle force data during low-level isometric contractions in diabetic subjects with different degrees of neuropathy. MethodsWe assessed 10 control subjects and 38 diabetic patients, classified as absent, mild, moderate, or severe neuropathy, by a fuzzy system based on clinical variables. Multichannel sEMG (64-electrode matrix) of tibialis anterior and gastrocnemius medialis muscles were acquired during isometric contractions at 10%, 20%, and 30% of the maximum voluntary contraction, and force levels during dorsi- and plantarflexion were recorded. Standard deviation and sample entropy of force signals were calculated and root mean square and sample entropy were calculated from sEMG signals. Differences among groups of force and sEMG variables were verified using a multivariate analysis of variance. FindingsOverall, during dorsiflexion contractions, moderate and severe subjects had higher force standard deviation and moderate subjects had lower force sample entropy. During plantarflexion, moderate subjects had higher force standard deviation and all diabetic subjects had lower entropy. Tibialis anterior presented higher root mean square in absent group and lower entropy in mild subjects. For gastrocnemius medialis, entropy was higher in severe and lower in moderate subjects. InterpretationDiabetic neuropathy affects the complexity of the neuromuscular system during low-level isometric contractions, reducing the system's capacity to adapt to challenging mechanical demands. The observed patterns of neuromuscular complexity were not associated with disease severity, with the majority of alterations recorded in moderate subject.

Biomechanical measures in participants with shoulder pain: Intra-rater reliability

Biomechanical measures are used to characterize the mechanisms of treatment for shoulder pain. The objective was to characterize test-retest reliability and measurement error of shoulder surface electromyographic(sEMG) and kinematic measures. Individuals(n = 12) with subacromial pain syndrome were tested at 2 visits. Five repetitions of shoulder scapular plane elevation were performed while collecting sEMG of the upper trapezius(UT), middle trapezius(MT), lower trapezius(LT), serratus anterior(SA) middle-deltoid, and infraspinatus muscles during ascending and descending phases. Simultaneously, electromagnetic sensors measured 3-dimensional kinematics of scapular internal/external rotation, upward/downward rotation, posterior/anterior tilt, and clavicular elevation/depression and clavicular protraction/retraction. Kinematic and sEMG variables were reduced for the total phase of ascending and descending elevation (30°–120°, 120°–30°), at 30° intervals for sEMG, and at every 30° discrete kinematic angle. The intraclass correlation coefficients(ICC) ranged from 0.08 to 0.99 for sEMG and 0.23–0.95 for kinematics. Correspondingly, the standard error of the measurement(SEM) and minimal detectable change(MDC) for sEMG measures varied from 2.3% to 103.8% of a reference contraction(REF-contraction). For kinematics, the SEM and MDC varied from 1.4° to 5.9°. Between-day reliability was good to very good, except for scapular internal/external rotation kinematics, and sEMG for the LT, UT, and SA. sEMG error values were highest (>25%REF-contraction) for most of the LT, UT, and SA variables. Kinematic error values indicate changes or differences of 2°–3° are meaningful, except for upward/downward rotation and internal/external rotation with MDCs of 4°–6°. Generally, data from the total phase of movement had better reliability and lower error than the data from sEMG interval or kinematic discrete angles.

Anaerobic Threshold by Mathematical Model in Healthy and Post-Myocardial Infarction Men.

The aim of this study was to determine the anaerobic threshold (AT) in a population of healthy and post-myocardial infarction men by applying Hinkley's mathematical method and comparing its performance to the ventilatory visual method. This mathematical model, in lieu of observer-dependent visual determination, can produce more reliable results due to the uniformity of the procedure. 17 middle-aged men (55±3 years) were studied in 2 groups: 9 healthy men (54±2 years); and 8 men with previous myocardial infarction (57±3 years). All subjects underwent an incremental ramp exercise test until physical exhaustion. Breath-by-breath ventilatory variables, heart rate (HR), and vastus lateralis surface electromyography (sEMG) signal were collected throughout the test. Carbon dioxide output (V˙CO2), HR, and sEMG were studied, and the AT determination methods were compared using correlation coefficients and Bland-Altman plots. Parametric statistical tests were applied with significance level set at 5%. No significant differences were found in the HR, sEMG, and ventilatory variables at AT between the different methods, such as the intensity of effort relative to AT. Moreover, important concordance and significant correlations were observed between the methods. We concluded that the mathematical model was suitable for detecting the AT in both healthy and myocardial infarction subjects.

Spectral analysis of surface EMG based on empirical mode decomposition

Muscle fatigue is a common experience in daily life. Some researchers have defined it as the incapacity to maintain the required or expected force. Obviously, force, power and torque recordings as direct measurements of muscle fatigue are difficult to be obtained in one experiment. The main issue when using conventional sEMG variables to quantify fatigue is their poor association with direct measures of fatigue. Therefore, there is a need to develop muscle fatigue approaches that relate changes in sEMG variables with muscle fatigue. The empirical mode decomposition which is a recent tool for the analysis of nonlinear and nonstationary time-series is presented.

Muscle conduction velocity, surface electromyography variables, and echo intensity during concentric and eccentric fatigue

Concentric (CON) and eccentric (ECC) contractions may involve different mechanisms related to changes in sarcolemma status and the consequent alteration of action potential transmission along muscle fibers. Muscle conduction velocity (CV), surface electromyography signal (sEMG), muscle quality, and blood lactate concentrations were analyzed during CON and ECC actions. Compared with ECC, the CON protocol resulted in greater muscle force losses, blood lactate concentrations, and changes in sEMG parameters. Similar reductions in CV were detected in both protocols. Higher echo intensity values were observed 2 days after ECC due to greater muscle damage. The effects of the muscle damage produced by ECC exercise on the transmission of action potentials along muscle fibers (measured as the CV) may be comparable with the effects of hydrogen accumulation produced by CON exercise (related to greater lactate concentrations), which causes greater force loss and change in other sEMG variables during CON than during ECC actions.

Multi-channel electromyography during maximal isometric and dynamic contractions

Motor unit behavior differs between contraction types at submaximal contraction levels, however is challenging to study during maximal voluntary contractions (MVCs). With multi-channel surface electromyography (sEMG), mean physiological characteristics of the active motor units can be extracted. Two 8-electrode sEMG arrays were attached on biceps brachii muscle (one on each head) to examine behavior of sEMG variables during isometric, eccentric and concentric MVCs of elbow flexors in 36volunteers.On average, isometric (364±88N) and eccentric (353±74N) MVCs were higher than concentric (290±73N) MVC (p<0.001). Mean muscle fiber conduction velocity (CV) was highest during eccentric MVC (4.42±0.49m/s) than concentric (4.25±0.49m/s, p<0.01) and isometric (4.14±0.45m/s, p<0.001) MVCs. Furthermore, eccentric MVC showed lower sEMG amplitude at the largest elbow joint angles (120–170°) and higher CV at the smallest (70–150°) elbow joint angles (p<0.05–0.001) than concentric MVC.The differences in CV and sEMG amplitude between the MVCs suggest that the control strategy of motor units differs between the contraction types during MVCs, and is dependent on the muscle length between the dynamic MVCs.

Application of the Glazer pelvic floor muscle evaluation protocol to patients with spinal cord injury

Objective To identify differences in the anal sphincter surface electromyography (sEMG)variables in spinal cord injury (SCI) subjects with different severities. Methods One hundred and ten SCI patients' impairments were classified as ASIA A,B,C or D using the International Standards for the Neurological Classification of Spinal Cord Injury.The evaluation was pedormed using sEMG equipment with an inserted anal sensor electrode and the Glazer pelvic floor muscle sEMG protocol.The sEMG variables were recorded and compared. Results There was no significant difference in sEMG variables between groups A and B,but the mean and maximum sEMG values of groups C and D in flick contractions ( 1 s),tonic contractions ( 10 s),and endurance contractions (60 s) were significantly higher than those of group A.Compared with group C,the mean and maximum sEMG values of group D were all significantly higher. Conclusions The sEMG data from the anal sphincter during contractions decreases significantly after SCI.Glazer's pelvic floor muscle sEMG protocol is a noninvasive and convenient real-time assessment.It is a useful complementary tool for quantitative assessment of the pelvic floor muscles of SCI patients. Key words: Spinal cord injury; Pelvic floor; Surface electromyography

Effects of Strength Training on Muscle Fatigue Mapping from Surface EMG and Blood Metabolites

this study examined the effects of heavy resistance training on the relationships between power loss and surface EMG (sEMG) indices and blood metabolite concentrations on dynamic exercise-induced fatigue with the same relative load as in pretraining. twelve trained subjects performed five sets consisting of 10 repetitions in the leg press, with 2 min of rest between sets before and after a strength training period. sEMG variables (the mean average voltage, the median spectral frequency, and the Dimitrov spectral index of muscle fatigue) from vastus medialis and lateralis muscles and metabolic responses (i.e., blood lactate, uric acid, and ammonia concentrations) were measured. the peak power loss after the posttraining protocol was greater (61%) than the decline observed in the pretraining protocol (46%). Similar sEMG changes were found for both protocols, whereas higher metabolic demand was observed during the posttraining exercise. The linear models on the basis of the relations found between power loss and changes in sEMG variables were significantly different between pretraining and posttraining, whereas the linear models on the basis of the relations between power loss and changes in blood metabolite concentrations were similar. linear models that use blood metabolites to map acute exercise-induced peak power changes were more accurate in detecting these changes before and after a short-term training period, whereas an attempt to track peak power loss using sEMG variables may fail after a strength training period.