 The objective of this randomized trial is to study the effect of stress on performance and the effect of repetition of simulation sessions on performance and stress. This study is a randomized controlled trial including 48 participants who composed 12 multidisciplinary teams MDTs. Each MDT was made up of 4 persons: an emergency physician, a resident, a nurse, and an ambulance driver who usually compose an emergency team of the French Emergency Medical Service EMS. 6 MDTs underwent 9 simulation sessions over 1 year Repetitive SIm Group. 6 MDTs underwent 3 simulation sessions over 1 year Control Group. Evidence of the existence of stress was assessed in 3 ways: salivary cortisol, Holter parameters, and psychological stress questionnaires. The impact of stress on overall team performance, on technical procedure, and on teamwork, is evaluated by specific validated scales. Detection of post-traumatic stress PTSD is performed by self-evaluation on the 7th day and after one month. The perspective is to concomitantly evaluate technical and non-technical performance, and the impact of stress on both. This is the first randomized trial studying repetition of simulation sessions and its impact on both clinical performance and stress as explored by objective and subjective assessments. The investigators expect that stress decreases team performance and that repeated simulation increases team performance. The investigators expect no variation of stress parameters regardless of level of performance. 