The Bridge is a technique present in just about every grappling art, going by many names including upa, bump, and buck. The particulars change from art to art but the goal is the same - use the hips to create momentum and space. A powerful action that can throw a novice grappler off, and can be used to disrupt a more advanced grappler's top game and balance if timed right, the bridge is used in a variety of ways.
Here is a basic video of how a bridge looks:
This basic technique is how bottom fighters move a fighter on top of them, creating space and momentum to then execute other higher level techniques. The bridge's power comes from the legs and core, both of which push the hips.
The bridge is taught in Brazilian Jiu Jitsu, Judo, and Wrestling to set up escapes, or in the case of competitions with pins, to keep the shoulder blades from touching the mat. Such is the case of the wrestling bridge, which makes greater use of the head to prevent from being pinned and then to roll on to the stomach.
Judo makes use of the bridge to escape pinning positions also. One of the primary pinning positions in Judo is known as Kesa Gatame, a very strong pinning position. It is extremely difficult to escape as the top fighter is able to put down extreme amounts of pressure and has excellent control of the bottom fighter.
This particular escape uses the bridge to first disrupt the top man's balance and create a bit of momentum. The bottom fighter then uses the space created by the bridge to get his hips under the top fighter and then uses a second bridge to roll the top man over.
Here is 2008 Olympic Judoka Matt D'Aquino teaching the escape.
This idea of disrupting base, creating momentum and then using a second bridge to escape is a principle used in other escapes from dominant positions.
One being a reversal from the bottom of mount. Again the bridge is used to first disrupt the top fighter's base and then reverse him. In this case the bottom man uses an explosive bridge to break the posture of the top fighter so that one arm can be trapped. The bottom fighter then bridges up to create momentum and roll the top fighter over.
Here is Rener Gracie teaching a long form of the escape, but the technique is contained in the first two minutes or so.
The bridge is also very useful for escaping side control but that was pretty well covered in the first Bloody Basics as it needs to be paired with the hip escape for it to work fully.
But here is UFC fighter and BJJ ace Demian Maia showing a few details on how to maximize the bridge's effect from side control.
The bridge is normally only useful when an opponent is physically on top of one's hips and thus is not used frequently when a fighter in in full guard. But there are sweeps that make use the basic principle of the bridge, like the "hip bump sweep". Used by Stephan Struve against Sean McCorkle, this sweep uses the bridge to off-balance and then roll over the top fighter.
Here is Rickson Gracie black belt Pedro Sauer with the details of this sweep:
In MMA there other factors to consider in grappling not present in these arts, even when practicing with strikes. The cage has become an integral part of grappling and techniques are being altered to accommodate that factor. So to conclude this entry I leave you with one of many bridge modifications that makes use of the cage in MMA.