An experimental protocol has been designed with specific exercises and the study of forearm muscles which are related with repetitive effort disorders (RED) and myalgia . The analysis and results obtained in a control group by multichannel surface electromyography (EMG) have validated this technique in order to be applied in patients such as diagnosis help or assessment of muscles changes during rehabilitation processes. Variables of interest from EMG signals have been defined and calculated during the protocol resulting repetitive. Multichannel surface EMG has permitted to obtain activation pattern of three extensor muscles and one flexor during fingers isometric flexion and to obtain the dependence on the pressure developed by different fingers which will be very interesting in the monitoring of myalgia in pianist musicians. Thanks to the electrodes matrices, muscle fatigue of the flexor and one extensor have been detected along endurance exercises. Finally, this non-invasive technique has been validated in exercises associates with RED and forearm muscles by detecting propagating action potentials with a good estimation of conduction velocity and, thus, permitting to obtain reliable data and information of muscle patterns.