Electromyogram Characteristics Research Articles

Altered sagittal plane kinematics and kinetics during sit-to-stand in individuals with knee osteoarthritis: A systematic review and meta-analysis

Knee osteoarthritis (OA) progression is associated with an increase in peak external knee flexion torque (EKFT) during gait. However, the difference in the peak EKFT between individuals with knee OA and age-matched subjects was unclear. Therefore, to understand the kinematics, kinetics, and electromyogram characteristics in individuals with knee OA, we conducted a systematic review and meta-analysis of sagittal plane-dominant sit-to-stand (STS) motion. PubMed, PEDro, CINAHL, and Cochrane CENTRAL were used. Fourteen articles (knee-OA group: n = 323, mean age = 65.0 years, mean weight = 79.2 kg; control group: n = 224, mean age = 64.4 years, mean weight = 70.4 kg) were included, and the pooled standardized mean differences (SMDs) were calculated using a random-effects model. Meta-analysis showed that individuals with knee OA present significantly lower peak EKFT (pooled SMD: −1.62; 95% confidence interval [CI]: −2.36 to −0.88), significantly large trunk flexion angle (pooled SMD: 1.04; 95% CI: 0.69 to 1.39), and no significantly lower peak external knee adduction torque despite the significantly larger lateral-lean angle to the less affected side (pooled SMD: 1.04; 95% CI: 0.69 to 1.39). The quality of evidence for all outcomes was very low. The descriptive synthesis indicates that STS motion in individuals with knee OA might be an unsuitable motion strategy for knee muscle activity, force utilization from multiple joints to the knee joint, and their influence on knee joint cartilage, despite their lower peak EKFT. This information can help to better understand movement strategies and to optimize treatment approaches for individuals with knee OA.

A Novel Validation Approach for High-Density Surface EMG Decomposition in Motor Neuron Disease.

This paper presents a novel two-source approach for validating the performance of high-density surface electromyogram (EMG) decomposition. The approach was developed taking advantage of surface EMG characteristics of amyotrophic lateral sclerosis (ALS). High-density surface EMG data from ALS patients can be divided to the sparse data set and the interference data set, with the former decomposed by expert visual inspection while the latter independently decomposed by the surface EMG decomposition algorithm. The agreement of the decomposition yields from the two data sets can be quantified for evaluating the surface EMG decomposition performance. The novel validation approach was performed for a recently developed method called automatic progressive FastICA peel-off (APFP) for high-density surface EMG decomposition. The APFP framework was used to automatically decompose high-density surface EMG signals recorded from the first dorsal interosseous muscle of ALS subjects. The common motor units independently decomposed from the interference data set and the sparse data set demonstrated an average matching rate of 99.18% ± 1.11%. The characteristics of the ALS surface EMG also facilitate a step by step illustration of the APFP framework for high-density surface EMG decomposition. The novel approach presented in this paper can supplement conventional two-source validation for accuracy assessment of decomposed motor units from experimental signals, which is essential for development of surface EMG decomposition methods.

Electrophysiological neuromuscular systemic characteristics of athletes in power training

This study is based on the analysis of electrophysiological characteristics describing the neuromuscular system of athletes during their training sessions, depending on their specialization and level of sport skills. It has been shown that the physiological changes securing the perfection of strength training in weightlifting athletes are mainly concentrated in the peripheral part of their neuromuscular system, namely, at the level of muscles themselves and neuromuscular junctions, and reflected in the electromyogram characteristics as arbitrary movements and M response parameters. At the same time, physiological rearrangements in combat athletes touch the peripheral mechanisms and the central component in the regulation of motor activity and are reflected in the parameters of visual and somatosensory evoked brain potentials. The results disclose an entire set of new important approaches to the functioning of different compartments in the nervous system and the neuromuscular apparatus in athletes of different specializations. They can serve as the basis for the development of practical recommendations on the organization of sports-specialized selection at different stages of athletic perfection, as well as for the physiological support of training process and methods of operating control.

The Comparison and Analysis of SEMG in Upper Limb Movement between Hemiplegic Patients and Healthy People

In this paper, the surface electromyogram (EMG) signal of the hemiplegic patients and healthy people were collected when completing upper limb movements, then the general EMG characteristic rules of healthy people in common action were analyzed, and the EMG characteristics of hemiplegic patients in time and frequency domain were extracted. By comparing and analyzing the EMG characteristics between the hemiplegic patients and healthy people, the results showed that the order and magnitude of muscle contraction of hemiplegic patients were not comply with the general laws of healthy people, which resulted in disorganized movement.

The effects of support deprivation and stimulation of the foot support zones on the lateral stiffness and electromyogram of the resting calf muscles

The lateral stiffness and electromyogram characteristics of the resting calf flexor and extensor muscles have been studied in 18 subjects during a seven-day immersion with and without mechanical stimulation of the foot support zones. It has been shown that as early as day 1 of support deprivation, the lateral stiffness steadily decreases in the m. soleus and, in contrast, drastically increases in the m. tibialis anterior. A mechanical stimulation of the foot support zones decreases the rate and degree of the changes observed in both muscles. The tight correlation of the changes in the lateral stiffness with the muscle activity suggests a significant dependence of these changes on the electromyogram characteristics at rest.

Perinatal model of human transition from hypogravity to Earth’s gravity based on nonlinear electromyogram characteristics

Interferential electromyogram (iEMG) was analyzed in healthy newborns (n = 29) during the first 24 h of life as a model of transition from hypogravity (intrauterine immersion) to Earth’s gravity (the postnatal period). Nonlinear methods of iEMG analysis (correlation dimension, entropy, and fractal dimension) reflecting the complexity, chaotic character, and predictability of signals from the leg and arm antagonistic muscles were used. The iEMG fractal dimension was shown to grow in all the muscles as the postnatal period extended, except the m. gastrocnemius during the first 24 h of life. Lower fractal and correlation dimensions and entropy were found to be characteristic of the flexors, especially at a low iEMG amplitude suggesting better congenital programming of the flexors compared to the extensors. It was concluded that the early ontogenesis model can be potentially useful for studying the evolution and the states of antigravity functions.

Differences in strength and surface electromyogram characteristics between pre-pubertal gymnasts and untrained boys during brief and maintained maximal isometric voluntary contractions.

The present study was aimed at investigating differences of maximal strength (F(max)) of the elbow flexors and characteristics of the surface electromyogram (EMG) between six gymnasts (G) and six untrained (UT) 10-year-old boys during brief and maintained maximal voluntary isometric contraction (MVC). The F(max) was estimated during 5 s MVC (maximal test, MT) and normalized to the cross sectional area (CSA) of the arm. The EMG signal of the biceps brachii was recorded during MT and during a 25 s maintained MVC (fatigue test). Values were calculated for root-mean-square (rms(MT)) and mean power frequency (MPF(MT)) of the EMG signal for the duration of the MT. For the fatigue test, MPF were normalized to the initial value (MPF(n)) and kinetics were expressed by the slope coefficient of linear regression. Although F(max) and F(max)/CSA tended to be higher for G than UT, the differences did not reach significance. The MPF(MT) was significantly higher for G [mean (SD)][136 (8) Hz] than for UT [125 (9) Hz]. The MPF(n) slope coefficients were significantly greater for G than for UT [-1.0 (0.2) and -0.5 (0.3), respectively]. When all the children were considered, F(max) was significantly correlated to MPF(MT) (r = 0.61). These results showed that gymnasts tend to have higher F(max) and F(max)/CSA accompanied by a significantly higher MPF(MT) and a steeper MPF downshift. Moreover, children with greater strength tended to have higher MPF(MT). It is suggested that spatial and/or temporal recruitment of more fatigable fast motor units could have been enhanced in G and more generally, that it could be a mechanism that would explains, in part, the level of force production in children.

Possible mechanisms of muscle cramp from temporal and spatial surface EMG characteristics.

In this study, the initiation and development of muscle cramp are investigated. For this, we used a 64-channel surface electromyogram (EMG) to study the triceps surae muscle during both cramp and maximal voluntary contraction (MVC) in four cramp-prone subjects and during cramp only in another four cramp-prone subjects. The results show that cramp presents itself as a contraction of a slowly moving fraction of muscle fibers, indicating that either the spatial arrangement of the motoneurons and muscle fibers is highly related or that cramp spreads at a level close to the muscle. Spectral analyses of the EMG and peak-triggered average potentials show the presence of extremely short potentials during cramp compared with during MVC. These results can also be interpreted in two ways. Either the motoneurons fire with enlarged synchronization during MVC compared with cramp, or smaller units than motor units are active, indicating that cramp is initiated close to or even at the muscle fiber level. Further research is needed to draw final conclusions.

Changes in the electromyogram of two major hindlimb muscles during locomotor development in the rat.

The development of the electromyogram (EMG) of tibialis anterior (TA) and medial gastrocnemius (GM) during locomotion was studied in normal rats from the onset of quadruped walking (postnatal day 10, P10) until P42. The objectives were to relate signal properties of the EMG and coordination of muscle activity to functional development of the hindlimb, which proceeds rapidly around P15. Both the EMG characteristics and the activation pattern showed marked changes with age. Initially, the EMG bursts were irregular and protracted. The activity level in the two muscles, in particular in GM, seemed to be low. Until P14, the motor units of GM showed a tendency towards synchronization. The EMG of TA consisted of an adult-like interference pattern from the youngest age studied. Although co-contraction of TA and GM was sometimes observed until P14, reciprocal activation of the muscles was evident at all ages. The timing of the alternating pattern became more accurate with age. The activity level in both muscles increased markedly from P15. These changes were reflected in the form factor (coefficient of variability) of the EMG and, to a lesser extent, in the power spectra. The time course of these changes bears a close temporal relationship to the development of locomotion. These results suggest that the degree of muscle activation is a decisive factor with respect to locomotor development. It is proposed that this is related to the maturation of supraspinal control.