You've heard a lot about the recent spate of upsets in mixed martial arts, which was punctuated by 4-1 underdog Houston Alexander's devastating 48-second thrashing of Keith Jardine at UFC 71.

You haven't heard as much about why these are happening.

I've chatted with several people with deep roots in MMA off the record over the past few days. Here are some of their thoughts on why more big-name fighters than ever seem to be going down to defeat:

1. The sheer number of events being run means more opportunities for more fighters. UFC ran five events per year as recently as 2004. Now they're looking at two dozen this year. If you have more than 200 matches in a year as opposed to less than fifty, there will be more upsets through sheer volume.

2. High-profile fighters can be scouted in minute detail by up-and-comers. If you're Joe Lauzon, for example, you grew up looking up to someone like Jens Pulver, watched all his fights on television, watched them over and over on DVD, and his success was a big part of the reason you got into the sport. Lauzon went into his 48-second TKO of Pulver at UFC 63 knowing all of his tendencies, strengths and weaknesses. Pulver, at best, might have seen some of Lauzon's clips kicking around on youtube. So many of these unknowns are coming in with a scouting advantage over their opponents.

3. Some of the top guys, quite simply, are getting a taste of the good life and aren't working as hard as they could to keep up with changing times. This could be the case with Mirko Cro Cop, who didn't even bother training in an octagon before his fights with Eddie Sanchez and then Gabriel Gonzaga. Cro Cop looked lost while he was trying to defend Gonzaga's elbows on the ground at UFC 70 while pushed up near the edge of the cage, right before the restart that led to Gonzaga's KO kick. Cro Cop, incidentally, has since purchased a cage for his future training.

4. Finally, perhaps the biggest factor, we're starting to get a hint of the sheer scope of how many talented athletes are getting into MMA these days. While some outlets just noticed that UFC exists last week, anyone who has been paying attention any length of time knows that interest in MMA has been steadily rising for years. What we're seeing now is the first generation of top-notch athletes who specifically got into the game wanting to be the next Matt Hughes, B.J. Penn, Fedor, Rich Franklin, etc.

Consider there are now groups like Team Takedown, which is recruiting NCAA champion wrestlers into MMA. They signed a pair of Oklahoma State standouts -- Jake Rosholt, the 2006 and 2007 national champ at 197 pounds; and Johny Hendricks, the 2005 and 2006 champ at 165 -- who will be training with Randy Couture.

With athletes of that caliber banging down the door looking to get in, don't expect the upsets to end anytime soon.

***

The idea that all the recent title fluctuation in the UFC is unprecedented simply isn't true.

Take a look at the results of title matches between UFC 46 on Jan. 31, 2004, and UFC 53 June 4, 2005:

46: B.J. Penn beats Matt Hughes for the welterweight title; Vitor Belfort beats Randy Couture for the light heavyweight title (on a fluke injury, but still a title change)

47: No title matches

48: Frank Mir beats Tim Sylvia for the vacant heavyweight title

49: Couture regains the LHW title from Belfort

50: Hughes beats Georges St. Pierre for the vacant WW title

51: Evan Tanner beats David Terrell for the vacant middleweight title; Arlovski beats Sylvia for the interim HW title after Mir had to forfeit the title due to his motorcycle accident

52: Hughes retains against Frank Trigg; Chuck Liddell beats Couture for LHW title

53: Rich Franklin beats Tanner for MW title; Arlovski retains against Justin Eilers.

From the time Penn beat Hughes to the time Franklin beat Tanner, you had eight new champions crowned in nine title fights over eight shows (one of which had no title matches), three of which were filling vacancies. In a span of more than 16 months, Hughes was the only man to step into the octagon as a UFC champion and leave with the belt.

Now, let's take a look at another eight-show span, from UFC 64-71:

64: Sean Sherk decisions Ken Florian for vacant lightweight title; Anderson Silva beats Franklin for MW title

65: Sylvia retains HW title against Jeff Monson: St. Pierre beats Hughes for WW title

66: Liddell retains LHW against Tito Ortiz

67: Silva defeated Travis Lutter in a non-title match, originally scheduled to be a title match, but Lutter missed weight.

68: Couture beat Sylvia for HW title

69: Matt Serra beats St. Pierre for WW title

70: No title matches

71: Quinton Jackson defeats Liddell for LHW title

Over this span, two champions retained; Silva won a fight which should have been a title match, and there were five new champs crowned, including a vacancy filler.

The current stretch of title changes may seem more pronounced because it has occurred over a seven-month span, but it simply has yet to match the 2004-05 run in terms of volatility.