Breathing is both a voluntary and an involuntary action, and the changes in breathing intensity or breathing stops has an influence on vegetative functions of the body during exercise. The aim of this study was to determine the possible changes in cardiovascular parameters when patients shortly stopped to breath at the beginning of exercise testing. MATERIAL AND METHODS. Two series of investigation were performed. During the first investigation, the psychomotor tonus was assessed, and the breathing frequency during exercising was monitored in the cohort of 27 healthy adult males who were recruited for the first time to be participants of exercise testing. All the participants performed the Roufier exercise test (30 squats per 45 s). A 12-lead electrocardiogram was continuously recorded during exercise and first two minutes of recovery, and arterial blood pressure was measured at each minute of experiment. During the second investigation, the influence of short breathing stop for 15 s on the changes in cardiovascular functional parameters during exercise test was evaluated. RESULTS. The results obtained during the study showed that patients who had increased psychomotor tonus stopped the breathing involuntary more frequently at the beginning of exercise testing. An involuntary or voluntary breathing stop at the beginning of exercising had an influence on the dynamics of cardiovascular parameters during exercise and recovery: heart rate increased more slowly; lesser changes in the JT interval of electrocardiogram, a trend toward an increase in the arterial blood pressure, and a significantly slower recovery of cardiovascular parameters were documented. CONCLUSION. An involuntary breathing stop caused the changes in cardiovascular parameters during exercise and recovery; therefore, functional status might be assessed not so accurately.