Introduction: Studies have demonstrated the presence of stress and post-traumatic stress among ambulance personnel, but no previous research has focused on the body’s reaction in the form of the change in heart rate of ambulance staff in association with specific occupational stress. Hypothesis: The purpose of this study is to investigate whether work as an ambulance professional generates prolonged physiological arousal that can be measured by heart rate in different situations. Methods: Twenty participants carried a pulse-meter in the form of a wristwatch, which continuously measured and stored their heart rate 24 hours per day for a period of seven days. All ambulance alarms that occurred during the test period were recorded in journals, and the participants completed diaries and a questionnaire describing their experiences. The alarms were divided into different phases. Correlations between heart rate in the different phases were computed. Results: Analysis of study data indicated a significant rise of heart rate unrelated to physical effort during an emergency alarm and response. This increased heart rate was noticed throughout the mission and it was not related to the length of experience the staff had in the ambulance profession. In addition, a non-significant trend suggested that alarms involving acutely ill children lead to an even higher increase in heart rate. In addition, this research showed that constant tension existed during sleep, while available for an emergency, indicated by a noticeable increase in heart rate during sleep at work compared to sleeping at home. Conclusions: A rise in heart rate was experienced during all acute emergency missions, regardless of a subject’s experience, education, and gender. Missions by themselves generated a rate increase that did not seem to correlate with physical effort required during an emergency response. This study shows that working on an ambulance that responds to medical emergencies is associated with a prolonged physiological arousal.