An essay by Bauke Livens covers some interesting points about circus history. I can’t say I agree with all of it and the use of launguage seems unnecessarily academic but I did like this quote…
…in the nouveau cirque, circus acts always interrupt the narrative. It is simply not possible to combine the two in one smooth whole. At the moment of physical danger (of presence), the story (the re-presentation) simply stops.
Read the essay here:
http://www.e-tcetera.be/first-open-letter-circus-“-need-redefine”
CircusGeeks.co.uk 
I don’t think that it’s an absolute that circus acts interrupt narrative. (I REALLY hate her use of “always.”) If done well, the circus acts should flow out of the narrative and help propel the story-line along. EG, mail room guy starts juggling packages in a cigar box routine to impress the clumsy secretary who knocked them over in the first place.
If done poorly, it’s much like the very early days of musical theatre, where songs didn’t always have anything to do with the plot.
JP on circus narritive
I agree with Stormtrooperprincess, the narrative and the action can meld. I’ve seen it happen. It’s not easy but that’s the challenge for contemporary circus makers.