Intervention : The intervention will last 2 years and will be implemented in partnership with the association SIEL (Sport, Initiatives, et Loisir) Bleu in 20 study centers located in large and medium-sized cities. It will include weekly exercise sessions in small groups, led by a qualified and specially trained instructor, and supplemented by simple exercises to do at home. The exercise program will focus on progressive balance retraining but will also include strength/resistance, coordination and flexibility training exercises.