Horses who buck while being lunged. There are several different reasons, which I’m sure many other trainers and horse advisers have mentioned – physical pain, playfulness or rowdy-ness, ill fitting tack, etc. One thing which I see is not often addressed, is the communication portion of interacting with the horse on the lunge.
Before I go down that lonely road, I want to first bring up the concept of a horse bucking. When we watch rodeos, we see horses do amazing maneuvers as they leap into the air – caused by a bucking strap. If your saddle is not equiped with one and you haven’t fashioned one by hand… then that is likely not the cause of your horse’s bucking – no matter how much it might resemble those famed rodeo horses! Bucking is not a maneuver of forward motion. It is a movement of upwards motion. It is just like rearing, with a little oomph, or a lot depending on your horse’s dedication. It engages more of the horse’s abdominal strength than rearing does.. but aside from the physical prowess your horse is showing, they are in essence the same ‘thing.’ (bear with me..)
Barring any physical issues or ill-fitting tack, that leaves playfulness and mis-communication as the key targets for why your horse is bouncing around on the end of that lunge line. Given that most of us learn how to lunge by doing rather than solid education taught by a professional (and not just your average riding instructor), it is not really that surprising that communication is still on the list of offenders. It is not a given when interacting with horses, least of all with 30 feet of line between you and a whip trailing at his feet… :)
Now, trying to link the two together – that bucking is an upward motion rather than a forward motion, and that most often mis-communication is a culprit… I’m going to give you the wham bam boogie! Not really, but…
The most common cause of a horse bucking on the lunge is that he doesn’t fully understand your desire that he moves forward, or is being blocked in some way shape or form (by you, his surroundings, or something imagined, you can decide on a case by case basis), while receiving increasing amounts of pressure from you (the ‘lunger’) until the pressure from behind is equal to the pressure in front, resulting in an upward explosion.
So… a simple solution? Clarify yourself by changing tactics. If your horse isn’t responding calmly and immediately from your request to move forward (or move *more* forward), perhaps go back to step one and teach him that you want him to move forward from the cue of the whip. Combine that with a double check that your position during lunging isn’t cutting him off (you should be behind the withers slightly if there was a straight line from the horse’s body to the center of the lunge circle), there is nothing blocking his way or path, or if needed do some confidence building to get rid of those scary ghosts (and I’m not talking about the confidence building that involves chasing him down with a blue plastic tarp… ;)).