It has been suggested that in creative activities, cognition and physical action are related to each other. This study focuses on this relationship in breakdance, which is a creative activity of artistic and acrobatic movements. For four months, we conducted field observations of practice sessions of three expert breakdancers, and held interviews with them to investigate the creation process of new and original movements. The video records of the 34 practices and the interview data were analyzed with respect to two aspects: 1) Whether or not the dancers performed important movements appropriately; and 2) What the dancers were thinking when generating new aspects of the movements. The results show an interactive process between the development of dance movements and the generation of ideas. The dancers gradually became able to perform the movements appropriately by generating new ideas, and they generated new ideas using the somatic sensation of the new movements.