Did you ever get a wild hair and just jump off the couch, after not running for awhile, and then run 6 miles? It feels great ... and then the next morning comes. The most important part of endurance isn't your finishing time (but that really matters if you want to be competitive). The MOST important aspect is your horse RECOVERING at vet checks, which means getting his pulse into an acceptable range, eating and drinking, showing no signs of lameness. The pulsing down can be the tricky part. The more your horse is 'in shape' the better they will pulse down. Some breeds, and some horses in those breeds, pulse down better than others with less conditioning than others, but just like people, the more you run or bike, the better you will get, and the better your heart will recover. However, you probably won't want to run the six miles the next day if you are sore, and horses are similar. They need to start slow and build up endurance. It takes a few months of going long, slow distances, working in some trotting up hills and different terrain. If you are fortunate and can get a horse pulse rate watch from POLAR, you can find your horses resting heart rate, average working heart rate, and then you can chart your horse's progress that way. If you are new to the sport and low on funds, the easiest is to buy a nice little stop watch and a stethoscope. When you stop for a quick break, take your horse's pulse (it will be higher if he's eating or drinking, so just have him stand still while you do it), and then take it again a few minutes later - the faster it lowers to his resting heart rate, the better in shape he is getting (you can take his resting heart rate in the morning or before the ride if you don't know it). You want to do a ride roughly as long as an average endurance loop, roughly 14-18 miles give or take where you are and the terrain - plan on each trail ride being 3-4 or more hours, and 2-5 days a week (5 is the high side, 2 is the low side). Training is a GREAT way to learn all about your horse, too, and his physical needs and limitations. Really pay attention to the signals he gives you on the rides about how he's feeling, and be prepared to listen. All the miles mean you need to be more attentive to his feet and H2O intake. BUT you will STILL need to be in control. I cannot stress enough that horses can get really HOT on an endurance ride since there will be horses of all abilities there and some will take off like their butt's on fire! This is why it is so, so, SO important to know your horse, do the training and know how to 'rate' him, and keep him at that rate during the ride. You can get swept up with people who have faster horses in better shape with more experience, and they will be trotting away from the vet check while you get pulled if you ask too much. But that is also what makes it fun - you and your horse, having a plan, being responsible and camping out with a bunch of awesome horse people is the BEST!!!!