Over-developed pectorals

[Hollymead]

Hello everyone. My mate owns a lovely 16.1hh TB x trotter called Ollie who, I've noticed, has over-developed pectoral muscles. He's your typical TB build, in good condition, but has these huge, sticky-out pectorals. Now what would they cause when ridden? And what, in turn, would cause them to become over-developed?
Ollie has a tendency to rush into canter, and can also get very strong and on the forehand when in canter. If he gets stressed, particularly when jumping, he can rear. Would any of these be related to his pectoral muscles? Anyone got any exercises my friend can do under saddle to reduce the pectorals?
I'm training as an equine massage therapist, and, whilst big and strong, the pectorals aren't really tense, just huge! Olly is also the most supple horse I have come into contact with - his carrot stretches are phenomenal!

[Wally]

I used to hunt a mare like this, she was a 15.2hh typical Irish hunter, TB X whatever.

She had a keel, that's the only way I can describe it, HUGE brisket stick out in front. She was always like that, summer or winter, fit or roughed off.

[Mehitabel]

are you sure it's muscle, and not just the way she is built? some horses do have a very protruding breastbone, like tha one wally describes.

[chev]

Could also be that he's pulling himself along rather than using his bum. Willow has rather impressive pecs too, mainly because her back end is weak so she compensates.

Lots of horses do just have that kind of build though.

[galadriel]

Pecs draw the torso forward after the horse extends his legs. Horses that tend to be on the forehand often have stronger pecs, because they're dragging themselves along rather than pushing from behind (as chev said). Such horses also tend to have very strong hamstrings, less so of the bicep and quadruceps.

If you can get some good balanced work out of the horse, pushing himself along rather than pulling....develop the quads so he's stronger in his back end...the pecs will probably not look so out of proportion any more. The rest of his muscles will strengthen :) as well.

[Hollymead]

Having had a good feel, I would definitely say it's mostly down to muscle, not bone. It's also very firm, ridgy muscle.
Galadriel - what you said was very interesting. Ollie has tense hamstrings as well as his big pecs, whilst his biceps and quads are very supple and soft. As an aside, his bracheocephalic muscle is like a piece of rock it's so tense.

[galadriel]

Overdevelopment of the muscles of the underside of the neck would go along with overdevelopment of the other muscles used in dragging a horse along on his forehand. That's the pecs, the hamstrings, the glutes just at the top of the croup.

A horse who's moving properly uses the top of his neck more, the top of his back, his abs, will use the muscles between the croup and the dock (rather than the ones on top of the croup and the hamstring) and the quads.

[Wally]

Sounds to me as if your horse might have a hip problem, sounds daft, but if there is a problem at the back as Galadirel says the front will compensate.

[Hollymead]

Wally - Ollie isn't mine, he belongs to a friend, but I'll ask the owner when she last had the chiro out, just to be sure.
Basically then, Galadriel, so long as it isn't a back/hip problem, I need to get the owner to start making Ollie work properly from behind? So that would start with getting him straight and going forward, but without rushing (his biggest fault), so she should be working on transitions, circles, spirals, shallow loops, leg yield, that sort of thing?