Other times, I use one-handed riding to test our connection and my own steadiness and correctness. Once we have a nice forward trot and Harley is reaching through his back and neck into the bit, I carefully place both reins in one hand, usually the inside hand.
The benefits are numerous...
Riding with one hand makes it very easy to ensure that my reins are even and that my horse is going to each side of the bit equally.
Riding with one hand prevents me from raising one hand or fussing with one side of the bit instead of just riding Harley forward from my seat and legs.
Riding with one hand shows me if my horse is not engaging one hind leg as much or is bracing with one shoulder, be it stiffness or unequal aiding on my part.
Riding with one hand tells me if I am riding Harley straight and forward.
Riding with one hand leaves my free hand available to gently encourage with the whip, keep rhythm, or make positional corrections such as feeling for softness in my lower back or checking that my bellybutton is pushing back toward my spine.
Riding with one hand makes it basically impossible to "cheat" with my hands. All of the aids must work in concert for Harley to carry himself and reach for the bit. When everything fits together and the puzzle is complete, even if it is only for a few strides, the feeling is very validating. After lots of practice, we can basically go all around the ring with little change in his frame or balance. This makes me happy!
Riding with one hand gives my horse the opportunity to show his level of understanding without corrections from the hand. This makes Harley happy!
Switching from one-handed to two-handed riding is also a useful coordination exercise. Harley was moving forward really nicely after a few minutes of one-handed riding and switching between the two. I like to put the reins in my inside hand so that I can still ask for inside flexion with my ring fingers. I initiate a circle this way and use my weight and legs to turn him. It is fun to ride different sized circles with just my body.
When we change direction across the diagonal, I slowly change to two-handed and then put my reins in the new inside hand. I use my free hand to tap with the whip if he not forward enough and adjust the rein length in my holding hand. Harley's neck gets really long and gorgeous when we ride this way. Sometimes I experiment with shortening his stride and then asking him to go back to working trot. Riding with one hand requires that I continue to ask him to go forward from my legs and seat even as he is shortening or collecting his trot. If I do just use my hand, then he hollows or backs off the contact. Riding with one hand keeps me really honest and gives me a lot of information about what I am doing and how I am doing it. Since I see my teacher very infrequently, this is a valuable self-evaluation tool.
A new thing to do this year would be to translate some of this to the canter. We have not done as much work with one-hand in the canter partly because his canter has not been as rideable as it is now and partly because I don't usually think to do it. This would be a good challenge and will, no doubt, show me some interesting things. I already know that Harley will like it very much.
After our one-handed warm up, I was really feeling the forward surge under my saddle. Harley's hind legs were pedaling underneath me with a pleasant, assertive feel. I tested the feeling by sitting the trot. He continued to push the saddle and my seat along. It felt very easy to sit this way and I felt very still. Sometimes we lost the feeling, but the change was very subtle. He would start to rush down the long side or tighten in anticipation of the canter (which I was not going to ask for yet). The feeling under the saddle changed before the tempo of his trot or tension became visible in his back. If I felt the surge disappear, he was sure to change his tempo and balance immediately afterward. Even though the trot probably didn't look that different, it became much less easy to sit and much less comfortable. I found myself starting to tip forward and collapse. It also felt like he was pulling the reins from me instead of pushing into the reins. The difference in feel was dramatic. The first sensation was steady yet powerful, the second was strong but unstable. I believe that this was my horse swapping from "back to front" to "front to back" movement and thinking. It was very interesting.
I found that I had the best luck encouraging him to stay in the former when my seat gave little nudges in coordination with my legs. If I just used my legs, he didn't really improve and adjusting my hands didn't work either. Harley seemed to best understand what I wanted from him when I used my seat. I began playing around with keeping him in front of my seat literally with little forward nudges. I also had to keep my seat closed in the saddle. I kept contact with the saddle and tried to support my upper body without leaning forward or back. If I lean back, he hollows and flattens onto the forehand. If I lean forward, he cannot carry himself properly and falls onto the forehand. There is not much grey area, which makes it very challenging, but when I achieve the correct position he rewards me instantly. When Harley moves this way we can do anything. Canter depart. Shoulder-in. Half-pass. It is just a matter of when and where and a flick of the ear.