In my previous post about finding Kat had popped a splint, I had mentioned doing more research to find out if driving horses were more prone to splints than horses competing in other events. In discussing bits with a couple of my friends, it was mentioned about the differences between riding and driving. Mostly it was the weight involved with each.
Riding- the horse is carrying the weight. It is easier for them to learn to balance you, shift their weight back on the rear end, lighten the front and move with engagement.
Driving- the horse is not carrying the weight, but rather they are pulling it. Whether it is a two wheeled cart or four, they have to lean into the breastcollar and pull in order to get things moving. They still have to maintain their balanced way of going, but keeping the weight on the rear end is a bit different. They are pulling with the front end, while trying to remain light enough to allow fluid movement.
With the added amount of digging in on the front end to get the cart moving, it wouldn't surprise me if driving horses are in fact, more prone to popping splints because of this. This is also the reason my mentor told me it is tough to get the proper amount of engagement in the horse and in their rear end when driving as opposed to riding. While I haven't really found any studies devoted to the likely occurrance of splints or similar front limb injuries in driving horses as opposed to riding horses, surely there is some connection. Just something to think about.