This paper examines an issue that has been little explored in ergonomics: safety in outdoor activities. Drawing on an analysis of guided mountaineering preparation, the paper focuses on studying and modelling feedback from professionals. Our premise is that preparation can be analyzed as a process of constraint satisfaction aimed at constructing manageable situations. This proposal is explored through a qualitative study conducted with mountain guides. Data were collected from 17 semi-structured interviews and 10 full days of filmed field observations, followed by individual and collective confrontation. The analysis focuses mainly on identifying the constraints of the preparation and the types of variables related to them. Five main types of variables which can be generalized were defined. A descriptive model was then produced, and safety issues were identified, along with corresponding strategies to improve safety.