Lead Sour?

Question
Hi! I have a problem with my 5 year old Quarter Horse mare. I have been training her since she was green broke. I got her about a year ago, and I have been working on canter leads with her. She will take her right lead immediately, but not her left. She has a scar on her back left leg from when she was a foal, but the vet declared it sound and strong. She is barefoot(strong hooves). I'm usually working in a round pen, and when I ask her to take her left lead she usually starts a fast trot or spins and shakes her head. I have tapped her with the crop and tried gentle leg pressure, and giving her a good boot. She just won't take it and we both end up getting frustrated. Please reply as soon as you can!
                                 Thank you, Lyndsey

Answer
Hi Lyndsey,
Thanks for writing in. Without being there and seeing what is going on it's hard to say exactly why she won't work with you on her canter lead. But I'll try and give some suggestions. I am assuming that she picks up the correct lead at a trot. You didn't mention it. If the vet has checked her out and reported her sound and no other medical problem exist then I would say it is either her just not wanting to do it or she doesn't know what you want her to do. The shaking of the head and spinning is her defiance. "No, I'm not going to do it and you can't make me". Horses are right sided or left sided just like we humans are. She sounds like she is right sided. Which means she learns faster and it's easier to do things on that side. Don't let your frustration get in the way. It's real easy to get caught up in it and that is counter-productive. Education begins where frustration ends. Now on to the suggestions.
I won't go into the mechanics of a canter other than it's a 3 beat gait. You probably know that already. In order for the horse to push off into a left lead and stay in it she will need to push off with her right hind foot. This in turn causes her left front foot to pick up with the shoulder. To do this you might try picking up the left rein and holding it out and up giving her a clear signal as to which way you want her to focus on. At the same time move your right foot back just behind the cinch and cue her with the heel. Don't punch her with it. This combination raises her left shoulder and moves the right hind in. She should pick up the correct lead at that point. If she balks on you and refuses to go, reach back with your right hand and "spank" her on the right rump. One good slap should get her moving. Don't whip her but just give a quick slap on the right rump. Be prepared to feel her jump forward though. Make sure you have loose reins and are not in her mouth. If the reins are making contact with her mouth and you give her the cue to move you would be sending a mixed  signal to her. She would be confused and thinking "what does this gal want me to do already??????" I would do this exercise in a controlled area such as a round pen or an arena. If in an arena, let her canter on a loose rein. Don't worry about where she goes and don't steer her. Just let her cruise around the place at a canter. Start out with only about five strides and then one rein stop her. I am assuming at this point you know how to one rein stop. Each time increase the distance she canters on that lead and shut her down with a one rein stop. To depart on the opposite lead you just reverse the cues. This may take some time so don't expect it to be perfect in the beginning. I have trained some horses that it took hundreds of times of doing this to get them to depart on the correct lead. Once she departs on the correct lead just canter her around in large circles in the direction of the lead. Example....left lead= left circle. Right lead=right circle. Don't make the circles too small in the beginning. Let her get use to it and grow into it.
I  hope this has helped you. If you still have problems with it and this doesn't work (not everything works for every horse) get back in touch with me and I can give you some other suggestions. You can also e-mail me at blpdoc82652@yahoo.com
My facility is Yazoo Equine Training.
Please let me know how well she responds....or doesn't. I like to follow up on these problems. Good luck and please stay safe.