Originally Posted by Celeste
It is not good for out of shape horses or out of shape people to do extremely long rides. An 8 hour ride would kill me. I think that anything over 7 or 8 miles is something that you need to build up to. Horses that are ridden in an arena may be in excellent shape and ready to go on long rides.
A horse accustomed to riding in an arena may be in good condition for that sort of riding, but (again) it depends on the type of trail/terrain you plan on tackling.
I wouldn't suggest taking a horse that has only done arena work out on a trail with a lot of hills. There is much more required of a horse (and rider) in terms of balance, use of muscles and overall fitness that you just cannot duplicate in the soft, even ground of an arena.
That's like thinking you're in shape because you walk on a treadmill at the gym, then trying to hike the whole Appalachian Trail.
I've seen "trail" horses that have only ever done flat trails/roads, whose owners thought they were in great shape, break down when they tried to go out and do a longer ride that required them to do a lot of climbing, or scrambling through tricky footing, or crossing through deep water. The horse just wasn't in condition for that kind of work.