**4. Analysis of a movement**

EMG enables us to record muscular activity, and it is often advisable to carry out a synchron‐ ized cinematic measurement at the same time. In this way, the two types of data can be contrasted and it is possible to establish:

In a training process, improvements in these parameters can be sought, follow-up carried out

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In particular, the performance of a task can be improved in terms of muscular activation and/ or in terms of muscular fatigue, based on the analysis of the frequency of the electromyographic traces observed [9]. It has to be remembered that the EMG does not provide us with muscular force parameters, although it is an indicator of the muscular effort made in a particular action [67,12-57,11]. In relation to this, it is important to stress that the relationship between EMG activity and effort is only qualitative [5]. Recently, experiments have also been carried out in the sports area on applications for purposes such as the evaluation of the type of muscle fiber

Muscular force is the amount of force a muscle can produce with a single maximum effort. Enhanced muscular force can lead to improvements in the areas of performance, injury prevention, body composition, self-image, lifetime muscle and bone health, and chronic disease prevention [16]. There are many cases in which knowledge of the relationship between EMG and force is desired. If the relationship between force and EMG amplitude is simply linear, a direct regression equation yields a relatively simple technique to control prosthetic

Ergonomists could assess the load on various muscles by monitoring the EMG activity. The relationship between EMG and force also seems to depend on the nature of the muscle studied, since some investigators have reported a linear relationship for the adductor pollicis and first dorsal interosseous and soleus, and a nonlinear relationship for the biceps and deltoid [68]. There have been other, numerous examples of observations of nonlinear relationships between

It is clear that when considering the possible shape of the EMG force relationship, one needs to consider various features of the movement, such as the type of muscle contraction; the size and location of the active muscles; their role as agonists, synergists, or antagonists; air temperature [71,19] and the numerous other physiological and technical factors that affect the

EMG has been a subject of laboratory research for decades. Only with recent technological developments in electronics and computers has surface EMG emerged from the laboratory as a subject of intense research in particularly kinesiology, rehabilitation and occupational and sports medicine. Most of the applications of surface EMG are based on its use as a measure of activation timing of muscle, a measure of muscle contraction profile, a measure of muscle contraction strength, or as a measure of muscle fatigue [72]. Only a handful of research articles using EMG techniques were published in the early 1950s. Today, over 2500 research publica‐ tions appear each year. The growth of the EMG literature and the availability of appropriate instrumentation and techniques might suggest that our understanding of the procedures used

and corrective measures or steps for improvement determined [5,13].

and the characterization of muscles [15,14].

limb function [19].

electromyogram [19].

force and EMG amplitude [69,70].

**4.2. Relationships between muscular force and EMG**

**4.3. Examples of current EMG studies in sciences of sports**

**Figure 2.** A research of lower extremity muscle groups [66] ( Photograph shot during a study by Sozen H. et al.).


The analysis of movement usually includes cinematic and kinetic study [52,47,41]. The cinematic study is responsible for determining the position, speed and acceleration parame‐ ters, both linear and angular. Different camera and marker systems are used for this purpose. A kinetic study determines the internal or external forces involved [41].

## **4.1. Evaluating sports performance**

Surface EMG is commonly used to quantify the magnitude and timing of muscle activation during various physical tasks, that has broad application in sport science research [44]. The fact that sEMG can analyze dynamic situations makes it of special interest in the field of sports [11]. The improvement in the efficiency of a movement involves the correct use of the muscles, in terms of both economies of effort and effectiveness, as well as in the prevention of injury. In a training process, improvements in these parameters can be sought, follow-up carried out and corrective measures or steps for improvement determined [5,13].

In particular, the performance of a task can be improved in terms of muscular activation and/ or in terms of muscular fatigue, based on the analysis of the frequency of the electromyographic traces observed [9]. It has to be remembered that the EMG does not provide us with muscular force parameters, although it is an indicator of the muscular effort made in a particular action [67,12-57,11]. In relation to this, it is important to stress that the relationship between EMG activity and effort is only qualitative [5]. Recently, experiments have also been carried out in the sports area on applications for purposes such as the evaluation of the type of muscle fiber and the characterization of muscles [15,14].
