When I was 12 I began to take horse riding lessons. I was with a group of six girls my own age who learned the basics and enjoyed the opportunity to make one lone trail ride every Saturday. At the time I knew nothing of sex or masturbating and had never experienced an orgasm.
One warm Saturday I was surprised to begin feeling a very nice but new sensation as I rode. I noticed that the sensation was connected to the horse's gait, and that if I rocked my body the right way I could increase the pleasure of the feeling.
I was absolutely amazed by this feeling. I began to think that it was only riding that could make it happen, and that I was the only one that had these wonderful feelings.
A month or so after making my amazing discovery I went riding behind our stable with only one other girl on the trail. It was a ride that took about an hour and I was absolutely distracted by the feelings I was having. When we returned, my fellow rider and new friend Susan told me that she noticed I was 'really enjoying' my ride. I asked her if she had the same feelings and she laughed. 'Why do you think I do this?' she responded.
Then she asked me if I finished myself when I was done riding. I asked her what she meant and she proceeded to explain what a climax was. We were brushing the horses and putting our stuff away at the time and we were alone in the barn.
'Come over here,' Susan said, 'and I'll show you.' She led me into an empty room, pulled her jeans down a bit, and exposed her vagina to me. It was obviously swollen and wet like mine always became when I rode. 'Here's what you have to do,' she said. She began touching her clitoris. I was fascinated and very aroused, and within a few minutes I was following her lead. Touching myself just as she was doing, I soon brought myself to a very powerful orgasm, my first ever.
When I had regained my composure we talked for a long time. Susan told me that sometimes she was able to climax while riding if she leaned into the saddle in just the right way. She also said that many girls had the same experience when they rode. Susan and I became great friends that year and masturbated several more times while watching each other.
She moved away a year later and I never had that kind of a relationship with another female.