This communication offers to present the study of a project which consists in participating in the reintegration of a highly precarious public . The objective is to offer a range of physical, sporting and artistic activities in addition to a social reintegration system. Activities whose mobilization would make possible to restore a weakened or even broken social bond (Paugam, 2017), the inclusion and the well-being of people suffering "from the absence of one or more of the securities" (Wresinski, 1987, 14). Our study aims to analyze this sport system established after the various confinements induced by the Covid-19 crisis. Also, it seeks to identify the effects of physical activity on this public as well as the conditionality of these effects. While the contribution of sport to the integration of individuals has sometimes been demonstrated scientifically and in some circumstances, it is necessary to "relativize and contextualize the effects" (Gasparini, 2008, 11) by analyzing the public concerned, understanding the meaning of the practice for this people and its real contribution to social ties. An ethnographic approach was favored: comprehensive interviews (Kaufmann, 2016) with the actors of the system; observations of physical activities sessions in three different associations for the homeless or former homeless from january to june 2022; biographical interviews (Demazière et Dubar, 1997) with certain participants to explain what leads them, more than others, to get involved in the practice of physical activities. Through this communication, we’d like to present the system and the reception the participants make of it but also, thanks to the biographical interviews, we want "to apprehend the object of the research from the inside" (Boumaza and Campana, 2007, 20) by highlighting "the systems of values and the normative benchmarks from which they are oriented and determined" (Blanchet and Gotman, 2015, 24): context elements, social biography, but also their daily life and their social conditions of existence that can influence their participation in the system and its effects.