Alwyn Cosgrove included the following metabolic workout in The New Rules of Lifting for Abs book, which I previously raved about.
It's perfect when in a time crunch or if you want to add the (no calorie) icing on top of an already awesome sweat session. Last week I threw it in before I taught a low-impact group exercise class.
At the start of a minute, complete anywhere from six to ten burpees. The goal is to complete as many as you can within about 20-25 seconds. Rest for the remainder of the minute (about 35-40 seconds). Repeat ten times for a total of ten minutes. Mine looked something like this:
0:00 - 0:25: 8 burpees
0:25 - 1:00: rest, feeling confident this will be a good workout
1:00 - 1:25: 8 burpees
1:25-2:00: rest, starting to breathe a little heavier
2:00 - 2:25: 8 burpees
2:25 - 3:00: rest, yep, heart rate's definitely up now
3:00 - 3:25: 8 burpees
3:25 - 4:00: rest, how many do I have left??
and so forth...
Beginners should start somewhere around four to six minutes, adding one at a time as their fitness improves. More advanced exercisers can add on a minute each week. Have fun!