Screen Inventory:
-Initial: Muscle Group Selection
-Secondary: Exercise List

Muscle Group Selection:
-User selects one muscle group -> List of 4 exercises generated
-User selects two muscle groups -> List of 2 exercises for both generated
-User selects no muscle group -> Error message displayed

Exercise List:
-List of 4 exercises for one muscle group
-List of 2 exercises each for two muscle groups