A stressful state can lead to symptoms of mental exhaustion and physical fatigue, detachment from work, and feelings of diminished competence. One of the health consequences of chronic stress at work is an increased risk of coronary heart disease. Emergency physicians subjectively complain of stress related to changes in work shifts. In occupational medicine, no marker of stress or fatigue has achieved consensus. Several potential biomarkers of stress have been described, but never investigated in emergency physician, who may represent a good model of stress due to the complex interplay between stress (life-and-death emergencies, which is the defining characteristic of their job), lack of sleep and fatigue due to repeated changes in shifts.The aim of this study was to compare HRV in emergency physicians working a 24-hour shift (24hS) or a 14-hour night shift (14hS), and in those working a control day (clerical work on return from leave). We will also follow these markers three days following each shift (D3/24hS and D3/14hS).