## 2 Materials and Methods  
### Experimental Procedure  
Fifteen volunteers with no evidence of current musculoskeletal disorders or those related to changes in muscle strength, pain, or a reduced range of motion were invited to participate in the study. After a narrow check-up of the recorded video and EMG files, only ten of them passed for further consideration--four men and six women. The main reasons for excluding the participants were serious EMG artifacts, spikes, incorrect starting and ending positions, and non-compliance with the set rhythm of the motor task execution. All of them were right-handed and performed a sequence of ten tasks with their right hand. The experimental protocol was approved by the Scientific Council of the Institute of Biophysics and Biomedical Engineering. On the day of the study, the whole procedure was explained to the subjects in detail, and they signed informed consent. Before each motor task, performance instructions were given, the movement was shown, and the participant performed several trials on their own before the recording of the EMG data and video began. The examination was conducted in a sitting position on a chair with a backrest and without armrests. The EMG transmitter was placed on the waist of the examined person, and electrodes were stuck to the muscle fibers of six muscles or parts of muscles. The system used was Telemyo 2400 G2 from Noraxon Inc. (Scottsdale, Arizona, USA), the surface electrodes were \"Skintact Premier\" F-301 (Archenweg, Austria), and the diameter of the circles was 30 mm. For better electrode adhesion according to the standards of EMG signal gathering, the skin was prepared in the following order--hair removal (if needed), alcohol whipping, and conductive gel application. These muscles were targeted--pars acromialis and pars spinata of m. deltoideus, m. biceps brachii, caput longum of m. triceps brachii, the surface lateral part of m. brachialis, and m. anconeus. Two elbow angles were recorded using a 2D goniometer. The sampling frequency during the experiments was 1500 Hz. A complete motor task protocol was designed to study the kinesiology of the upper limb in detail. For the present study, only the first half of the protocol was studied, where movement performance is in the sagittal plane. Each task was completed in 1 min. Motor tasks in the full experimental protocol (FEP):  
A person's starting position is always the same. The volunteer is seated on the chair with their shoulders leveled and their arms resting calmly beside their body and their palms facing their hips. Their knee joints are bent at 90 degrees, and their feet are placed firmly on the floor. Their gaze is directed forward. TASK 1. Hold the starting position for 1 min. The goal here is to see the power and stability of the EMG signal. TASK 2. Within 1 min, the examiner takes the subject's arm and passively moves it into several positions. From these positions, the volunteer performs the maximal isometric contractions against the maximal manual resistance to elicit the maximal muscle response. Resistance is applied to the distal part of the bone lever. This task is further used for the normalization of the EMG signals. The next six motor tasks are cyclic movements in the sagittal plane, divided into four phases. The first phase is flexion from the starting position to the possible maximum upper position. The thumb points in the direction of movement. The second phase is the pose of holding the reached upper position for 5 s. The third phase is extension from the maximal upper flexion to the starting position. The fourth phase is the pose of holding the starting position for 5 s. The number of repetitions for cyclic movements is limited to 1 min, i.e., the subject carries out as many repetitions as possible in this time. The duration of the holding positions is always 5 s, and the active phases have different durations.