Electromyographic Study on Positive and Negative Works. : I. Method of the Integration of EMG Potentials.

Abstract

There are two main types of electrodes in the electromyographic study of muscle activity in the human. The one is the surface electrode and the other is the inserted electrode. Since each electrode has its characteristics, the surface electrode is generally applied to the study of physical education and kinesiology. On the other hand, EMG (especially recorded by the surface electrode) can deal only with the qualitative analysis of muscle activity. Therefore, several investigators have tried to record the electrical activity of muscle quantitatively. Namely the integrated electrical activity has been recorded. Lipold and his coworkers (1952) showed the mechanical integration with planimeter. Bigland and Lippold (1954) performed the integration with a modified Miller's circuit. In Japan, Ikai (1963), Abe (1963) and others have tried it. The purpose of this study is to make a more complicated integrating circuit and analyze the relation between the integrated EMG and the muscular tension. Fig.1 is a block diagram of the integrator. EMG is picked up on the skin by a pair of standard electrodes placed over the muscle in question. This is amplified, rectified and then led to the integrator. The output of the integrator is recorded on the pen writing oscillograph. Fig.2 shows the response of the integrator to an input of constant voltage. It is clear that the increasing wave form of output (integrator) is proportional to the magnitude of the input voltage such as 1mV, 2mV and 5mV. Using this integrator, the authors intended to secure that the relationship between the tension exerted by the muscle and integrated EMG was linear. In this study, the flexion of the elbow joint was picked up. Namely the relation between the weight held by wrist and the muscular activity in the biceps and the brachioradialis was observed. The subject was a healthy man (35 years old). He supported the various weights with his wrist at the right angle of the elbow joint in sitting position isometrically. The weight varied from 5kg to 30kg. The subject exerted his strength over 10 seconds at least adjusting the magnitude of the weight. In the past, some of the experiments appeared to show a quantitative relationship between the applied weight and the amplitude of the EMG tracing. In man and his coworkers (1952)obtained a parallelism in a biceps brachii of human contracting isometrically. In the same year, Lippold and his coworkers (1952) described that the electrical output as revealed by measuring EMG with planimeter closely parallels the tension when the gastrocnemius-soleus contracted isometrically. Bigland and Lippold (1954) reported that the relationship between electrical activity and isometric tension of the extensor muscles of the finger was linear. Basmajian and Latif (1957) electromyographically showed that the three muscles came into action such as the biceps brachii, the brachialis and brachioradialis. Inman and his coworkers (1952) reported only about the biceps in flexion of the elbow joint. In the case of the present study, EMG and its integration of the biceps and the brachioradialis were recorded by the surface electrodes. Fig.3 shows the recording of EMG and integrations according to the magnitude of the tension. Fig.4 is the diagram of the relationship between them. Total in the diagram is the sum of the electrical activity of the biceps and that of the brachioradialis. The relationship between the integrated electrical activity and the isometric tension is proportional. And the results of this study show the same inclination as Lippold and Bigland already reported in the gastrocnemius-soleus and the flexor of the finger.