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Two immersion interventions at a specific, long-term site are set out and described : the first was ergonomic and was carried out in conjunction with the polar expedition to ensure the operation of the Concordia scientific station in the Antarctic ; the second, which involved providing psychological assistance, concerned the French sailing team during training and competitions spread over two Olympics, including the events at two Olympic sites. At a remove from these two interventions, their frameworks and intervention rationales were compared, as were their methodological models and the procedures used, and the modalities and constraints of the expertise brought in. A final discussion will try to contrast and compare these two paradigms and the ethical benchmarks of researchers.