In addition to being rooted in an enactive conception of the activity (Durand & Poizat, 2015; Theureau, 2003), one of the originalities of this research is to focus on the learning experienced by cadets while they are engaged in spaces of action that do not encourage their activity, but on the contrary hinder it: the hardening training course. The purpose of this training is to make these officer cadets experience simulated situations of physical, emotional and psychological over-stress, presenting similarities with their future professional life. In order to better understand how, within such a simulation device, officer cadets experiment with their ability to maintain individuals’ dispositions to act, we analysed the engagement modes of the trainees in their learnings to command among aversive environments. The results show that alongside the well-known forms of executory and exploratory engagement, a “conservatory” mode of engagement appears, the aim of which is to preserve the conditions for perpetuating the action and capacities of each officer cadet. This research leads to the formulation of principles for the design of trainings whose aim is to prepare professionals to deal with the unknown, the unexpected and even the unbearable.