Automatic Decomposition Electromyography Research Articles

EMG Changes During Graded Isometric Exercise in Pianists: Comparison with Non-musicians

Long-term piano training might induce some biochemical and structural adaptations in the intrinsic muscles of the hand or change the motor strategy of the nervous system. The main purpose of this study was to analyze whether the intrinsic muscles of the hands of pianists and sedentary controls differ in electromyographic characteristics at different strengths. Fifteen college piano students and 15 sedentary controls were asked to sit on an examination bench and perform first dorsal interosseous muscle contractions for 1 minute. The motor unit potentials were recorded during various percentages of maximal voluntary muscle contraction (MVC) by automatic decomposition electromyography. The pianists demonstrated a significantly higher firing rate, shorter duration, and higher amplitude of motor unit potentials during minimal muscle contractions than the sedentary controls. But when comparing all the parameters at other degrees of contractions, the pianists were found to have significantly higher firing rate only at 25% and 50% of MVC, and higher amplitude at maximal contraction than the control group. The amplitude at maximal control contraction was higher in pianists than in controls. These results imply that high-frequency and highly efficient muscle fibers are recruited in pianists when minimal muscle contractions are performed, which also indicate that by using smaller motor units, pianists may delicately control their fine motor performance.

Effects of temperature on motor unit action potentials during isometric contraction.

The effect of temperature on motor unit action potential (MUAP) configuration and recruitment was studied using automatic decomposition electromyography (ADEMG) recordings from a concentric needle electrode placed in the first dorsal interosseous (FDI) muscle of 10 normal adult subjects during isometric contraction. Focally cooling the FDI resulted in prolonged MUAP duration (P < 0.001, ANOVA), a finding congruent with those of Buchthal. Focal ulnar cooling at the elbow resulted in the increased MUAP frequency. In contrast to previous studies, there were no significant differences in amplitude or turns. Greater understanding of normal motor unit electrophysiology is necessary to improve diagnostic accuracy of EMG testing.

Automatic decomposition electromyography in idiopathic inflammatory myopathies.

Automatic decomposition electromyography (ADEMG) is a commercially available software package with installed reference values that enables the objective measurement of motor unit action potentials (MUAPs). To assess the diagnostic yield of this package in idiopathic inflammatory myopathies (IIM) we performed bicepts brachii ADEMG in 17 patients with polymyositis, dermatomyositis and inclusion body myositis. Results were compared with those in 12 controls, and with the results of conventional EMG of the biceps and other muscles. Decreased mean values for MUAP duration occurred significantly more frequently in IIM patients than in controls; other MUAP characteristics did not differ. In IIM patients, decreased mean amplitude and increased mean number of turns occurred significantly less frequently on ADEMG than did corresponding abnormalities on conventional biceps EMG. Decreased mean values for duration and amplitude, and increased mean values for number of turns were seen significantly less often on ADEMG than corresponding abnormalities on conventional EMG of four different, individually chosen muscles. Overall evaluation of ADEMG resulted in a diagnosis of "possible myopathy" in 1 and "probable myopathy" in 8 patients, whereas overall evaluation of conventional EMG led to a diagnosis "suggestive of IIM" in 13 patients. We conclude that, although measurement of mean MUAP duration might be valuable in IIM diagnosis, our results do not favour the use of biceps brachii ADEMG and the installed reference values for the diagnosis of IIM. We suggest modifications to improve ADEMG's applicability.

Quantitative electromyographic analysis of the external urethral sphincter using automatic decomposition electromyography on normal subjects

Motor unit action potentials (MUPs) of the external urethral sphincter muscle during cystometry were analysed on six normal males. Electrodes were of concentric needle type having the exposed tip surface of 0.07 mm2, and the potential changes were analysed by automatic decomposition electromyography (ADEMG), for isolation and characterization of unit discharges. Number of analysed units was as follows: Two at rest, 4 at first desire to void, and 6 at maximum desire to void. Number of the recorded units and the firing rate were increased along with the degree of bladder filling. Average MUP figures as follows: Amplitude of 206 microV, 8.3 msec. duration, and 5.4 Hz firing rate at rest; 246 microV, 9.7 msec and 7.3 Hz at first desire to void; 277 microV. 9.7 msec and 7.2 Hz at maximum desire to void, respectively. It is concluded that external urethral sphincter maintains its urinary continence by excitation of the neuromuscular units, and by the increase in the firing rate of individual MUP during bladder filling.

Quantitative electromyographic analysis of the human external urethral sphincter: effect of alpha-adrenergic agents

External urethral sphincter electromyography (EMG) during bladder filling was quantitatively analysed using automatic decomposition electromyography (ADEMG). These include 7 normal volunteers, 7 patients with outlet obstruction, 9 with sphincter dyssynergia, and 7 with pelvic nerve injury (PNI). Recruited number of participated motor unit action potentials (MUPs) at maximum bladder filling was significantly larger than that at rest in the normal volunteers, patients with outlet obstruction, and sphincter dyssynergia. In patients with PNI, MUPs were not increased. The MUP amplitude did not differ significantly among groups during bladder filling. In PNI group, MUP duration at rest tended to be larger than those in other groups. Firing rates at first desire to void and at maximum desire to void were significantly increased than that at rest in every groups except the PNI group. Effect of alpha-1 adrenergic blocking agent, phentolamine (5 mg intravenously), was examined on 3 patients with benign prostatic hypertrophy (BPH), and in 4 patients with sphincter dyssynertia. Effect of an alpha-1 adrenergic stimulating agent, norepinephrine (5 microgram/min intravenously), was also evaluated on 5 patients with PNI during bladder filling. Immediately after administration of phentolamine, number of MUPs was decreased in BPH and sphincter dyssynertia groups. But in 2 paraplegic patients having reflex bladder with sphincter dyssynergia, number of MUPs did not decrease. Even with the continuous intravenous administration of norepinephrine for the elevation of the blood pressure, number of MUPs did not increase in any PNI patients. Effect of intravenous administration of phentolamine to induce urethral pressure elevation and the recording of the evoked EMG from external urethral sphincter by electrical stimulation of the penile dorsal nerve was tested on 4 patients without PNI before and after the administration. Phentolamine lowered urethral pressure at membranous urethra, but no significant change of evoked urethral pressure response and EMG activities was observed. It is concluded that the decrease of MUP after phentolamine administration is due to the relaxation of periurethral part of external urethral sphincter, and clinical denervation supersensitivity of the external urethral sphincter after norepinephrine administration was not demonstrated in the PNI groups.

A comparison of turns analysis and motor unit analysis in electromyography

We compared the results of turns analysis and motor unit analysis on 4056 electromyographic interference patterns (IPs) from normal subjects and patients with neuromuscular disorders. The motor unit analysis involved decomposing the IPs into their component motor unit action potentials (MUAPs) using automatic decomposition electromyography (ADEMG). We checked the accuracy of the decompositions by attempting to reconstruct some of the IPs from their identified MUAPs using computer simulations. The simulations revealed that ADEMG typically identified more than 60% (but not all) of the MUAPs in a given IP. Both turns and MUAP properties showed regular and related changes with force, age, muscle, and recording electrode type. The number of turns in each IP was highly correlated with the number of active MUAPs ( r = 0.65), the mean MUAP firing rate ( r = 0.72), the mean number of turns per MUAP ( r = 0.34), and the product of these 3 properties ( r = 0.83). The mean amplitude change per turn was highly correlated with the mean MUAP amplitude ( r = 0.82), but also depended on the number of turns per MUAP. Due to the lack of a one-to-one relationship between the turns analysis properties and the MUAP properties, the turns analysis properties by themselves did not provide sufficient information to infer unambiguous physiological information about motor unit morphology or firing behavior.

A study of automatic decomposition electromyography (ADEMG) in Duchenne muscular dystrophy

A study of automatic decomposition electromyography (ADEMG) in Duchenne muscular dystrophy

Motor unit firing rates and firing rate variability in the detection of neuromuscular disorders

We have used automatic decomposition electromyography (ADEMG) to study 41 muscles in 29 patients with well-defined peripheral and central motor disorders. In motor neuron diseases motor unit action potentials (MUAPs) showed increased amplitudes, firing rates and firing variability. Relatively large MUAPs sometimes were not identified by the computer program if they lacked sufficient high-frequency signal content, or were too variable in shape. In myopathies the MUAPs showed reduced amplitudes, durations and turns, and sometimes dramatic increases in firing rates. Also, the mean number of MUAPs per recording site was often increased, indicating excessive recruitment. In polymyositis (the best studied myopathy) the nature and magnitude of the MUAP shape and firing abnormalities were usually similar at different levels of contractile force, suggesting that motor units are affected without regard to recruitment order. In upper motor neuron paresis (multiple sclerosis), the shape properties of the MUAPs were normal, but mean firing rates were reduced, and firing variability increased. These findings confirm many of the traditional criteria for distinguishing neurogenic from myopathic disease electrophysiologically at the level of the individual MUAP. In addition, they demonstrate the potential diagnostic sensitivity of MUAP firing rate measurements for detecting neuromuscular dysfunction, and for differentiating between some cases of central and peripheral paresis, but not for distinguishing peripheral neurogenic from myopathic weakness, since firing rates tend to increase in both. Increased firing rate variability may be a marker of central or peripheral neurogenic weakness.

Properties of motor unit action potentials recorded with concentric and monopolar needle electrodes: ADEMG analysis.

We compared the configurational and firing properties of 7270 motor unit action potentials (MUAPs) recorded with either concentric (CNE) or monopolar (MNE) needle electrodes from the brachial biceps and anterior tibial muscles of 10 healthy young adults (mean age 27 +/- 4.5 years) using automatic decomposition electromyography (ADEMG). In both muscles, mean MUAP amplitude, rise rate, and number of turns were significantly greater when recorded with MNE (paired t-test, P less than 0.001 in each case). Similar findings were observed at all three tested levels of isometric contractile force: threshold, 10% of maximum voluntary contraction (MVC), and 30% MVC. In contrast, there was no significant difference between electrode types on measurements of mean MUAP duration or firing rate (P greater than 0.05 in each case). These findings indicate that it is acceptable to generalize normative data on MUAP duration and firing rate from one electrode type to another, but that measures of MUAP amplitude and complexity require independent normative databases.

Influence of contractile force on properties of motor unit action potentials: ADEMG analysis

We have used automatic decomposition electromyography (ADEMG) to measure the configurational and firing properties of 13 206 motor unit action potentials (MUAPs) in the brachial biceps, brachial triceps and anterior tibial muscles of 30 healthy adults (22 men, 8 women; mean age 48.6 ± 16.9 years, range 20–76) at three levels of isometric contractile force: threshold, 10% of maximum voluntary contraction (MVC), and 30% MVC. In all muscles, the increment in contractile force from threshold to 10% MVC was associated with a significant ( P < 0.05, paired t-test) increase in mean MUAP firing rate and number of turns per MUAP. The increment from 10% to 30% MVC led to highly significant ( P < 0.005) increase in mean firing rate, number of turns, amplitude and rise rate. Each force increment was associated with an increase in the number of simultaneously-active MUAPs per recording site; and with a significant decrease in mean MUAP duration in all muscles, due to noise-dependency of the duration measurement. Quantitatively, the changes in MUAP properties with force were comparable to or exceeded the effects of age, gender differences, or intermuscular variability. Test-retest measurements 2 years apart in a subgroup of young adults showed good correspondence of mean MUAP properties with force standardization. These results demonstrate that contractile force is a major determinant of MUAP shape and behavior properties, and so must be precisely measured or controlled in clinical EMG studies.

Automatic decomposition electromyography (ADEMG): validation and normative data in brachial biceps

We describe a new, automatic method (ADEMG) for decomposing EMG interference patterns into their constituent motor unit action potentials (MUAPs), and quantitating the configurational and firing properties of the MUAPs. ADEMG is fast (90 sec analysis time for a 10 sec EMG epoch) and efficient (33–98% of MUAP occurences correctly identified) because of 4 signal-processing innovations designated digital prefiltering, high-resolution wave from alignment, firing-time analysis and interference-cancellation averaging. Validation experiments are described involving recruitment/derecruitment of low-threshold MUAPs, and single-fiber-triggered averaging. Normative data are presented for 2000 MUAPs from brachial biceps (mean 9.7 MUAPs per site) at 3 levels of isometric contraction (7%, 15% and 30% MVC) and contrasted with normal findings obtained using traditional, low-threshold MUAP analysis. The main advantages of ADEMG are (1) speed of data acquisition and processing in the clinical setting; (2) ability to analyze both low-and high-threshold MUAPs during moderately strong muscular contractions; and (3) MUAP firing-rate information.

Automatic decomposition electromyography

Automatic decomposition electromyography