Modelling Gof Observer patterns in UML

I am modeling my project, which I will subsequently implement in Java, using UML. My project involves managing a gym. More specifically, I am currently modeling my GoF Observer diagram. By what I've understood, I can't allow my Graphic Controller, with the models (entity), correct me if I'm wrong. On the other hand, if I let my application controller to implement the Observer, how can I notify the graphic controller that an exercise changed his status? Here I put my two ideas: