Every brand has now understood the importance of animating its community and above all making it more influential. This report explains how Fitness Park, the leading network of gyms in France (450,000 customers, 200 gyms), uses growth hacking to mobilise 400 micro-influencers without paying them and to actively animate 2/3 of its customer base without paying large sums. At the beginning of 2017, the brand embarked on a real digital transformation, entrusting the agency, among other things, with the creation of its mobile application, making it possible to offer content and practical services (class diary, gym contacts, customer account access and some home-made training programmes). The brand modernised its CRM and e-commerce site at the same time, but it quickly realised that the digitalisation it had just started was part of the \”basic contract\” and was therefore no longer significantly differentiating.