Now that we have developed the walk, it is time to move on to the trot. Same principals apply, we want the horse moving forward with freedom of movement in a balanced and relaxed way of going. We will still be looking for the overstep in their stride and something else we will be looking for is that the legs on the diagonal are moving in hamony with each other. What does that mean?
When looking at pictures of horses moving at the trot, not only will there be overstep and sometime overreaching, (see photo below) but if you were to draw a line thru the cannon bone of the front leg and hind leg on the diagonals- they should be parallel. Looking at the legs in the air, if the front leg is in front of the parallel and going to be on the ground before the hind leg, the horse is heavy on the forehand. This is often paired with the horse having No overstep. This is typical as the horse hasn't learned how to move properly yet and if you look at them, most of their weight is in their front end anyways.
Developing the walk, we taught the horse to reach up under them with their hind legs and use their rear end more, engaging it and pushing themselves forward. With their hind legs coming up under them, it allows their front end to become lighter. Think of it like a teeter totter. If you're sitting in the middle and you want the board behind you to go down (rear end coming up under you) the board in front of you (the horses front end) will obviously go up making the horse lighter and more forward. In the photo of Kat, although he is built slightly downhill, he is moving in such a way that his withers are actully a touch higher than his rear end.
It is important to remember to be fair to the horse here. Their muscles are in development and they won't be able to hold this frame and way of moving for long. At first you may get a couple of strides at best in either direction. One reason is because 1) the horse is trying to figure out what you're asking them to do and 2) because they aren't used to actually doing it. We are trying to develop *New* muscle memory in their way of going. It takes time. Compare it to your own riding. Think about where you were at when you fist started and how far you've come to where you're at today. Think about the different muscles you use and how they remind us we weren't using them when we took a week or two off from riding.
Part of long line work is being able to take up contact and to remain soft and following when needed. Long line work is similar to riding. Same cues with your hands and reins, you're just on the ground, not in the saddle. If you have done ground work and lunging with your horse, they will be familiar with you asking for different gaits. As you ask them to move forward into the trot you will also take up contact. You're asking them to move up into the bridle and giving them a reference point of where they need to be.
This part is a balancing act for both of you. The horse finding that *sweet spot* where they are balanced in their movement and for you, where you know when to use a little more rein to bring them back, voice and body language to push them forward or when to praise them for doing it right and leave them alone otherwise. Too much of one, not enough of the other and some days it will feel like you're never going to get there. It won't happen overnight and some days it takes more to get it than others. It's not a race and keep in mind, you're just setting up the base of things to come later on.