How do I keep him from going into a canter on the lunge line?

I ride a horse at another barn with ex racehorses. I took a lesson on the one and hadn't been on him for close to a year. My instructor took us into the new arena where we have to work from now on. I'm still on the lunge line at her place with no reins. The horse I ride doesn't have a long enough mane to hold onto, and so now I'm used to gripping to the front of the saddle. My main problem is that this horse likes to break into a canter when we're trotting, which really throws me off balance when I have nothing to hold onto but the saddle and that doesn't help at all. So yesterday at my lesson I ended up falling off once and almost two other times because he keeps cantering. How can I prevent this from happening with no reins and no control over the lunge line?

You need to keep your post light, slow and close to your saddle. Concentrate on lengthening your leg down and wrapping your leg around his barrel (but not clamped on) to give you a good base. When a horse gets quick, peoples tendencies are to lean forward and curl up in a ball. Make sure you keep your body tall and try to use your body and seat (and voice)to help slow your horse. Just curious...How long have you been riding? I was just curious to see if your trainer is doing this exercise with you too soon...

So, the trainer has the line, right? I would think you're trainer would know how to correct it. It's also a balance thing. If you lean forward, it's more natural for the horse to start in a canter. Try leaning back a bit if he does. It may feel unnatural at first, but that's what you want... you want the horse to feel unnatural so he will start trotting again to equal out his balance to match yours. Other than that, your trainer really has most control on foot if you don't have reins.

This may not be the horse for you to learn on lunge if he keeps breaking into a canter, just a thought

I've only been riding for about a two years now but it's really on and off. I usually ride once every 2 weeks and if something happens where a trainer (i have two) can't teach lessons then I'm off for a while which happens quite frequently. At the one stable I ride at I am really good at posting and can canter with an older mare I ride. She isn't as fast as lets call him Joe is. I'm really not used to riding Joe but Midnight I can ride all the time with no problem. This is at another stable where I have reins to use and have never been on a lunge line at. Since Midnight is slower it's a lot easier to ride but with joe it's really hard for me to balance because he's so fast. My instructor says she doesn't want to help me a lot in controlling Joe because she's trying to teach me how to keep my balance and control the horse at the same time. I think it's a little too soon for both but my instructor likes to mix things up a little.

I've tried leaning back when he gets too fast but then I lose my balance even more and it causes me to slip out of the saddle. I'm trying to get better at my halts and slowing Joe down but yesterday I couldn't coordinate at all after that fall.