Introduction/Objective. Numerous studies on surface electromyographic (sEMG) signals in response to different respiratory parameters, particularly on sternocleidomastoid (SCM) muscles and diaphragm (DIA), indicated the promising advantages of their simultaneous monitoring with possible applications in the analysis of their correlation. This motivated ? detailed statistical analysis of the average power (PAV) on sEMG signals during prolonged breath-holding, simultaneously measured in the SCM and DIA areas. Methods. The physiological breath-holding method was applied to 30 healthy volunteers, with sEMG of SCM and DIA regions measured before, during, and after the breath-holding exercise. All the subjects were sitting in an upward position, with nostrils closed by the right index finger and thumb during breath-hold. To synchronize the records, the user would press a special switch using the other hand at the beginning and at the end of breath-holding experiment. The average power of sEMG (PAV) was measured for each 500 ms signal window. Results. The PAV remains constant before and 3 seconds after the exercise. During the ending of breathholding, at least one region had the PAV afflux of a minimum of 91%. Student?s t-test between SCM signals shows a significant difference of p < 0.001, while the DIA lacks it. Although the results showed that SCM is the dominant region in 76.67% of cases, the exclusive PAV afflux in the DIA region was detected in precisely five cases (16.67% of the total namber of participants). Conclusions. Our research concludes that there is the necessity of simultaneous measurement of SCM and DIA to observe dominant changes in sEMG during breath-holding. The physiological response of the respiratory center can be observed by approximately doubling PAV in one of SCM or DIA regions.