Imprison a ballet dancer and expect him to dance with no class?
Dancers take class every day, in addition to rehearsals and other physical training. After his accident and convalescence, the dancer played by Barishnikov in this film would have been out of shape and greatly in need of routine and daily classes if he was going to get in shape to perform. His 'workouts' with Gregory Hines' tap dancer looked interesting, but they were not the kind of training a dancer needs to dance as Barishnikov did in the opening sequence of the film.