Pony behaving strangely...

I've recently started riding a horse for a friend of mine (who doesn't ride her very often) and who has just moved away so is a bit preoccupied. I've ridden Jaz before and she was always fine, but last week I rode her twice and both times she behaved very strangely. She would be very reluctant to move up to trot and when she did she would flick her tail and throw her head up and jog about so that I kept losing my seat.

She'd be fine in canter and walk. I wondered if maybe she was lame (to my knowledge, I've never ridden a lame horse, so I wouldn't be certain) but I lunged her and she didn't seem bothered at all in trot. I'm wondering if her saddle is perhaps pinching her. She's put on a lot of weight recently and I imagine it would be worse with a rider in the saddle but I'm not sure.

Does anyone have any idea what the problem could potentially be, or has experienced similar problems with their horse?

She also coughed a few times when we moved up into trot, if that's any help.

Thanks for reading and I'd really appreciate any ideas.

Alex :)

You've already mentioned the ones I would be looking into - especially the saddle not fitting which is very common after some weight gain.

If the horse is lame there would usually be some visual indication of a limp or a head bob when the horse steps on that sore leg. But mild lameness could still be a potential culprit since horses are great at hiding soreness.

Maybe her back is out and she needs an adjustment?

Thanks, I appreciate your suggestions. I'll have to get in touch with the owner and tell her my worries, I think.

If it is the saddle that's causing her trouble, should I just try and get her to lose some weight or does she need a new saddle fitted?

It depends. How long do you think it will take her to lose weight? Maybe you could borrow a wider saddle until she has lost some.

On the other hand - has she just gained weight or also muscle mass? Sometimes muscling up can change their back enough to make the current saddle not fit and they need a new one.

Not sure what kind of saddle you have, but some of the english and aussie saddles can be reflocked/stuffed by a professional to compensate for the issue.

I think it's just weight rather than muscle. It's an English saddle and I've sent a message to the owner to see if we can maybe get a saddle-fitter to come out and have a look. Thanks for your help :) I'm going to the yard later and I may post some footage of me trotting on her to see what's really going on.

Any updates?

The owner says she has always done it, but I've never experienced behaviour like this from her before so I'm going to have to look into it more. All the horses in the yard seem to have cracked feet, including the one I ride (quite badly), so the farrier's come to deal with it. I'm hoping that's part of the reason.