Physical activity and sports are a central part of individuals’ lives throughout the life cycle. During adolescence, its regular practice may contribute to the development of healthy adult lifestyles, decreasing chronic disease incidence. Therefore, the reasons that drive adolescents to start practicing sports in a certain club may be multiple and understanding such causes can be important to design and implement public policies to promote active lifestyles for everyone. In this article, we report the core findings of a research on why young athletes do sports, how they choose their team-training club and how COVID-19 has had an impact on their routines. From a methodological viewpoint, a questionnaire was developed and sent to sport clubs located in NUTS2 Centro Region, Portugal, and results were analyzed through the use of geographic information systems and statistical analysis, namely association tests (Chi-square test), difference tests (Mann–Whitney test and Kruskal–Wallis test), logistic regression and descriptive analysis. Findings show that family, age group, friends, proximity to sports facilities, teammates, and club conditions are the factors that influence adolescents the most. In short, external factors have a significant preponderance to practice physical activity and choose a sports’ club. These findings can provide useful insights for clubs, coaches and policy-makers to become more aware of the relationship between sports practice and accessibility to sports halls, as well as the athletes’ behavior and their connection with the club and basketball practice. As such, these findings can motivate the design of initiatives and strategies to boost sports practice and to find ways for clubs to attract more adolescents.