Immediately after my fourth set of matwork (TM) this morning, I clocked my HR at 45 bpm for 15 seconds. Margins of error (+/1 5 bpm) notwithstanding, that's a HR of 180. And by just about any estimation, that's also supposed to be my maximum heart rate.
I know that the mathematical models (and I've looked at a few) are flawed. But I doubt that they are off by that much (10 bpm? 15? at the most?). What is all the more interesting is that the maximum heart rate should be adjusted lower for seated activities like bicycling or rowing. Joel Jamieson at 8WeeksOut suggests that for typical grappling/wrestling/jiu jitsu purposes, taking 5 bpm off the top is more accurate. This makes it all the more likely that I managed to hit a maximum level in today's training.
The point behind threshold training, according to Joel, is to "increase the aerobic system's maximum rate of ATP regeneration so more power can be produced aerobically." It does this by raising your "anaerobic threshold, and power at ANT, thus delaying the point at which anaerobic processes begin to dominate."
I think of it as being as explosive and agile as possible while remaining in the aerobic zone, which is crucial over the course of an 8-10 minute match (not including overtimes). You want to spend as little time in the anaerobic zone as possible, since it is harder to "live off the aerobic land" so to speak when you are in that zone. At the same time, you have to exert. So the trick is to be able to increase your the peak aerobic level you will be able to compete at. It's like being able to raise your speed limit: faster, but still legal.