This is a doozy for sure. You have to rule out WHY she is lazy. Laziness is a symptom. Is she bored? Sore? Unmotivated? Mad? Etc..
Once you find the "issue" then you can treat it. For a mad horse, you have to let them "win" a battle so you can win the war. For a bored horse, you have to do something different, go outside, set up some obstacles, etc.. For a sore horse, call the vet. An unmotivated horse needs to be motivated (think, carrot and fishing rod - I have tried this, it can work! Eventually a pat and a "good boy" can replace it).
As much as beating the tar out of the horse might work, your going to end up with a resentful horse that doesn't enjoy its work. And it will stop working. I have seen horses welted up like they'd stumbled upon a beehive that still don't move.
You might also resort to some.. *ahem* alternative?? Solutions. Plastic bags on a whip are good, so are fire extinguishers, fog machines, and Styrofoam.. just as a few ideas. If the horse wants to "fight" instead of "flight", we have to activate the "flight". Grab mane though because you do not want to stop the horse once it starts going.
PS I also like the idea of tying the mare to a bigger horse!! Make a quick release knot though!
She's not sore, I've flexion tested her, gone all over her back etc. and there is nothing at all coming up. The only injury she's had has been a fractured skull a few years ago when she was reaching under a rail to get grass and spooked, smacking her head on the rail.
As for boredom or frustration, well I doubt that she is either. She lives in a very big grassy paddock with plenty of trees and two 'friends' during the day, and comes into a roomy stable with a large yard attached at night, were she can see and talk to her 'friend' who is in the stable/yard next door. She is taken out fairly often into the forrest for trail rides with her companion.
She seems like a happy go lucky type of horse in the paddock, it is her work ethic that needs improvement by the looks of it.
I certainly havent got to the point of belting her one to leave welts, for the same reason that you said above, they eventually blank out to it. I don't want to get to the point of using brute force on her, because if that doesn't work then I've trapped myself.
She's not a spooky mare, and in the stables getting tacked up you can just about tie plastic bags to here ears and she doesn't care, so I'm not sure if spooking her with the bag would help much, it might though!!
I don't have a problem with accidentally gobbing them when they leap off as a result of a strong forward cue! Having had a few ottb's that have no idea what a leg means, I've certainly sat my fair share of equine aerobics with no reins!!
I'll give her a go with aplastic bag on the whip and see how that works out.
I'm a bit dubious about tying her to another horse, she can be a bit of a grumpy bugger and I would worry that she's going to bite the gelding and wind up with a broken leg as a result of the resulting kick! But if nothing else under saddle works I may have to resort to that.
My arab cross is just like that when he is out of work. Won't move at all, no matter what you do. I have had a few people get on him with the same results. Everyone except my dad, who had only ridden a few times. He can get on and Richie will happily trot whilst my dad holds the saddle...
Lunging was the same. Tried the plastic bag on the end of a whip and he didn't even blink. The only thing that worked was having another horse in the arena. Didn't matter whether he was following or not. I did that for a couple of weeks and once he started getting a little bit fitter I could ride him without another horse in the arena. And suddenly he seemed to know understand how to lunge as well.
Might not work with such a stubbon and lazy horse, but one horse I rode was stubbon as all hell. But he loved being patted, so when I got what I wanted he would be patted and praised and cuddled like he'd just cleared the worlds biggest show jumping round, but not every time he got what he wanted. Sometimes it was just a little pat when he was doing well and a carrot after the ride, might help. I'm not sure?
One thing I didnt hear you mention- spurs!
I have been riding 10 years, owned one for 4 months, in the mean time I have had my fair share of unresponsive horses!
Wear spurs, get someone witha lunge whip and good luck!