I sometimes do a "round-less" training like the KB classes at my gym (yeah, there's girls in it, but at full power I get good and tired, and have some nice "scenery" while I take a 10-sec. breathing break)...
...in between rounds, esp. when Bas dares to tell you to do shadowboxing during your break, do a calisthenic ex., like 10 push ups or 10 burpees, or 20 crunches and bicycles or 20 V-ups with a medicine ball, alternating legs and slamming it in to your shins (my favorite ab routine). You still get a little break, and vary the routine.