The theme is the <em>main idea or the underlying meaning</em> of a literary work. Sometimes is stated directly, other times indirectly. It's an opinion expressed on the subject. Theme and subject <em>are not</em> the same. <em>Subject</em> is like a foundation of a literary work, and the theme could be his personal opinion. <em>The readers should explore the theme, by analyzing characters, plot and other literary devices.</em>
Just "martial arts and acrobatics" doesn't specify the moves. By adding "those in", it shows that the <em>moves</em> in martial arts and acrobatics are what's similar.
