Sounds like something to be found in the cranial cavity, doesn't it?
IIRC, the bloke who designed it was Japanese. It's a form of
High Intensity Interval Training. Take any exercise (preferably appropriate for cardio or high # of repetitions - in my case it's kettlebell ballistics), and do it as hard as you can for 20 seconds, then take a 10 second rest, then do it again, you get the idea. I prefer to use a 1:1 work-rest ratio as of the moment, because I've tried the 2:1 with the 12kg and 16kg KB's and it took well over 15 minutes before my heart rate went down. Don't think I'm quite ready for that yet.
Try it with push-ups, squats, or even burpees or mountain climbers!
I'm not too sure what can be crammed into 15-20 second intervals with regard to sparring, but I have incorporated a similar concept into my training. I space 5 minute gaps between rounds and squeeze in a 3-minute kettle-bell routine in between consisting of quick pulls (swings, snatches, cleans) to gas me out and force me harder. The remaining two minutes are divided into 2 1-minute breaks before and after the mini-routine. Done wonders for me endurance and work capacity since then.