CORRELATION BETWEEN ELECTROMYOGRAPHIC ACTIVITY AND STRENGTH OF THE FLEXOR MUSCLES OF THE WRIST

INTRODUCTION: In analysing the electromyographic (EMG) signal, researchers are often led to interpret variations of the signal as variation in strength of muscle contraction. However, the relationship between the force exerted and the electrical activity of a muscle are not well established. This is due to the considerable variation of data acquisition and processing techniques, the detection site of the muscles analysed, as well as the alterations in their length and the type of contraction. The object of this paper was to evaluate the correlation between electrical activity and muscular strength. METHODS AND PROCEDURES: The flexor muscles of the wrist of the non dominant member of 21 female volunteers (mean age = 21 years, sd = ± 1.5) with no history of skeletal muscle dysfuntion, were analysed. The EMG signal was captured by active surface electrode (DELSYS), over the belly of the muscle in the longitudinal sense of the fibres, having a gain of 10 Hz. The electrode was coupled to a 16 channel 12/36 electromyograph (AqDados - LYNX TECNOLOGIA ELETRÔNICA LTDA), which permitted a gain of 50 Hz. The system bandwidth was 10 to 500 Hz, with an overall gain of 1,000. The data acquisition rate was 1,000 Hz. In order to eliminate possible interferences, a ground electrode was coupled to the distal segment of the forearm. Muscular strength was measured by means of a load cell (model MM/50 kg, KRATOS), placed perpendicularly in the center of the palm surface of the hand. The electrode and the load cell were connected to a 16 channel signal acquisition system (AQDADOS 4.0, LYNIX). The temperature of the room was kept at 23ºC, ± 1. The EMG registers and the strength were collected simultaneously. Result were obtained from the average of three repetitions, shown in RMS and Kgf respectively. The data was collected with the hand fixed to a device which limited the wrist to 45º of flexion and 45º of extension, providing an isometric contraction. RESULTS AND DISCUSSION: The results demonstrated a positive correlation between electromyographic activity and strength of contraction (r = 0.76) in the 45º flexion position, whereas, for the 45º extension position, the correlation was not significant (r = 0.23), considering the sample analysed. The data suggest that there is a positive correlation between EMG and strength, depending on the position of the muscle analysed

Electromyographic (emg) Activity Of The Vastus Medialis Oblique (vmo) And Vastus Lateralis (vl) Muscles In Hip Adduction Exercises

The purpose of this study was to investigate whether the VMO muscle had greater EMG activity than the VL muscle in maximal effort isometric contraction of hip adduction with knee extension at sitting position and decubitus lateralis. The electrical activity was measured on 15 healthy subjects (24.4 ± 4.1 years old) without prior hip and knee pathologies, using a 8 channels Nicolet Electromyograph and Beckman mini surface electrodes. The EMG recordings were analysed according to Basmajian's classification, giving percentage degrees of intensity. The results showed that the EMG activity of the VMO muscle was not significantly greater (test t of Student at 5% of significance) in both exercises of maximal isometric hip adduction when compared with the VL muscle. These findings, within the experimental conditions used, suggest that the maximal isometric hip adduction exercises with knee extension did not produce a selective strengthening of the VMO muscle.11

A physiotherapeutic approach to craniomandibular disorders: a case report

This is a case report of a 19-year-old female who presented with a unilateral weakness of the right masseter muscle evidenced by electromyographic examination. The presence of a mandibular deviation to the right during opening because of this weakness was treated with neuromuscular electrical stimulation (NMES). After the physiotherapeutic treatment, the electrical activity of the right masseter muscle increased during function and the mandibular deviation disappeared. Electromyography (EMG) can have a useful role in the determination of the muscular profile, and for evaluating therapeutics.29326827